Tropical Atlantic Update

Rina passes over Cancun, weakens to a Depression

2011-10-28T09:02:00.001-06:00

Since yesterday's update, Rina became even less organized and lost what little deep convection it had. This was well-timed for Mexico though, since Rina made landfall on Playa del Carmen (the mainland city directly west of Cozumel) at 03Z today (late Thursday night for them) then passed over Cancun. Its 9-hour traverse over land, combined with the increasingly hostile environment, was responsible for the downgrade to a 30kt Depression at 15Z today. All that remains is a tiny harmless low-level swirl just off the northeastern tip of the Yucatan peninsula. For a very Wilma-like origin and track, thankfully the intensity didn't follow suit.

The image below shows a vertical cross-section taken along the shear vector (southerly) from one of the regional hurricane models (HWRF's 06Z analysis). The fields shown on there are the wind speed (shaded) and relative humidity (lines). It's easy to see how weak and shallow the vortex is, and the intrusion and overriding of very dry air... the analyzed shear is 27kts too. This is not an environment that a storm can redevelop in.

Rina is forecast to lose its remaining tropical characteristics and degenerate to a remnant low very shortly, meandering around in the same vicinity due to weak steering flow.

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Rina downgraded to Tropical Storm

2011-10-27T10:51:00.001-06:00

In a battle against increasing vertical shear, Rina was downgraded to a 60kt tropical storm at 15Z today. The center is located just south of Cozumel and heading NNW at 5kts. You can also track it on Cancun's radar: http://smn.cna.gob.mx/radares/cancun/cancun.php

Now that it has weakened and the convective area associated with it has shrunk drastically, it is steered by different layers of the atmosphere. Deeper systems are steered by a deeper layer, and weaker/shallower systems are steered by a lower and shallower layer. That said, the forecast track now calls for Rina to stall in place, just meandering around in a loop waiting for some stronger steering flow to pick it up. The track plot in the map below shows forecasts from 3 dynamical models, and the NHC forecast is basically an average of these. The thin light lines are prior 00Z forecasts and can be ignored. The official intensity forecast also follows the model guidance closely: gradual weakening over the next several days.

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Rina nearly a major hurricane

2011-10-25T16:11:00.002-06:00

In the past day, Rina has intensified to a 95kt hurricane, with a high likelihood of reaching 100kts... it would become the season's 4th major hurricane. Visually, it has become a beautiful symmetric storm, with delicate outflow cirrus expanding uniformly away from the center.

It has another couple of days to enjoy a low-shear environment, then as it heads further north toward Cuba, the upper-level winds become quite a bit more hostile. But in the meantime, the ocean below it is extremely warm not just at the surface, but is warm quite deep too (that minimizes upwelling effects that slow-moving systems are prone to). The map below shows the depth of the 26C water... Rina's current location has some of the deepest warm water in the entire Atlantic basin.

The forecast is still quite tricky because of the weak steering environment. In the next few days, it should continue its slow crawl to the N-NW, but after that, its future depends on whether or not it gets "picked up" by a passing mid-latitude trough. If it does, it will make a turn to the NE and head for Cuba and then Florida... if it doesn't, it should meander slowly to the west or even stay approximately stationary.
Basically... Mexico, Cuba, and Florida should all be watching this very closely.
Some additional strengthening is still possible, and for at least the next day, there's no reason Rina can't strengthen quite a bit.

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Rina becomes season's 6th hurricane

2011-10-24T13:01:00.001-06:00

In what was a somewhat expected rapid intensification (based on satellite presentation), Rina was upgraded to a 65kt hurricane at 18Z today. The central pressure is 991mb, and it's still crawling north at 4kts. And again, given its appearance and environment, it's quite likely that additional intensification will occur, perhaps reaching Category 3 status by tomorrow. In the visible satellite image below, you can already see an eye forming:

Full zoop (zoomed out):
http://rammb.cira.colostate.edu/ramsdis/online/loop_640.asp?product=tropical_ge_4km_visir2_floater_2

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Rina forms in western Caribbean

2011-10-24T09:03:00.002-06:00

The disturbance off the coast of Nicaragua that I mentioned in Friday's update has gotten much better organized... and on Sunday at 21Z was upgraded to TD18, then six hours later, to TS Rina. This is the 17th named storm of the season; climatologically by this date we have had just ten named storms.

At 15Z today, Tropical Storm Rina's intensity is 40kts, with a 1001mb central pressure... and an appearance that suggests some hefty intensification can be expected. It's currently located north of the eastern tip of Honduras, and the forecast track calls for a very slow crawl toward the northern tip of the Yucatan peninsula. The majority of models bring this system up to hurricane intensity by Wednesday.

This time of year, this location, and this track forecast are very similar to Wilma (2005)... but so far, we aren't dealing with a Category 5 hurricane. At Rina's position, Wilma was a Category 5 storm six years and five days ago. This map below is for Wilma... NOT Rina:

There's also a disturbance in the far eastern Caribbean that is worth keeping an eye on...

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Disturbance festering in southwestern Caribbean

2011-10-21T09:02:00.000-06:00

For nearly a week now, there has been an area of disturbed weather in the extreme southwestern Caribbean. It's origins appear to be a combination of a tail of a cold front and the ambient monsoon depression. There is a 1010mb Low associated with the disturbance, and the low-level center is approximately 200 miles off the Nicaraguan coast.

The system is in a low-shear environment, and the shear is expected to remain below 20kts for at least the next several days. The SST is and will be nearly 30C. There is not yet a lot of model guidance for this, but the global models indicate that it will develop and VERY slowly crawl northward toward Cuba as it intensifies. Certainly something to keep a very close eye on, since the western Caribbean during time of year has birthed some infamous Category 5 hurricanes: Hattie 1961, Mitch 1998, and Wilma 2005. The plot below shows the tracks of 11 storms that formed in October in the western Caribbean and became major hurricanes. Note the relatively tight track pattern... north toward Cuba and Florida (Hattie, Mitch, and Wilma are the 3 that first went west before recurving/dissipating). If named, the next name on the list is Rina (replaces Rita from 2005).

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Philippe becomes a hurricane after 12 days

2011-10-06T09:25:00.001-06:00

The first advisory was written on Philippe on Sept 24th, and since then, it has fluctuated in intensity from 35-60kts, but never dropped to a depression, and never made it to a hurricane... until this morning. At 15Z today, Philippe's estimated intensity was 70kts and 985mb, making it the 5th hurricane of the season. It's located about 415 miles southeast of Bermuda and moving NNE at 8kts.

However, this is also its last gasp as a tropical system. Over the next couple of days, it will encounter SSTs nearing 20C and vertical shear up to 50kts and it will become an extratropical storm then finally merge with its mid-latitude trough.

To support the 70kt hurricane classification, the microwave image below (from NRL in Monterey CA... at 1023Z this morning) shows what appears to be an eye and eyewall, and definitely some strong tightly-curved rainbands. The latest visible and infrared images are indeed showing a slightly clearing eye... I included an enhanced visible image from 1445Z below the microwave image so you don't just have to take my work for it!

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Ophelia turns extratropical, Philippe still a TS

2011-10-03T11:41:00.000-06:00

At 15Z today, the final advisory was written for Ophelia... 18 days after it left the African coast and 13 days after it was first classified as a tropical storm. Over the weekend, the storm reached a peak intensity of 120kts and 940mb (Category 4) as it passed 140 miles east of Bermuda. It's presently a 50kt extratropical cyclone and just passed over Newfoundland (exactly the same landfall location as Maria 17 days ago!).

Early Saturday morning, it did indeed pass very close (just 5.4 miles west!!!) to Buoy 41049 as I mentioned. The buoy reported 40ft waves, wind gusts up to 100kts, and a pressure of 952mb. The plot below was made using hourly data from the buoy:

Philippe is still hanging around, and is still a tropical storm. Surprisingly though, on Sunday morning, it was nearly a hurricane! It reached an intensity of 60kts and 993mb, but has since weakened again to 55kts.

It is forecast to continue westward for another 24-36 hours, then recurve abruptly into the north central Atlantic.

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Ophelia now a major hurricane

2011-09-30T09:51:00.002-06:00

Against all odds, the storm that was not even a Depression three days ago is now a 100kt major hurricane... the 3rd major hurricane of the season. Since the 27th at 21Z when Ophelia regained Depression status, the maximum winds increased 75kts and the central pressure fell 48mb. More impressively, we can narrow the time window down to the past 12 hours, when the winds increased by 25kts and the pressure fell 19mb.

This rapid intensification was not anticipated by dynamical models, statistical models, or human forecasters, and goes to show how little we still know about what makes these storms tick. One run sticks out, which suggests it was more serendipitous than skillful... HWRF's 18Z run on Sep 27th was fairly accurate:

Ophelia is now forecast to maintain Category 3 intensity for another day or so, then gradually weaken and become extratropical by early next week as it gets whisked into the north central Atlantic by a strong mid-latitude trough. Something to keep an eye on is Buoy 41049, which should get a near hit from Ophelia on Saturday afternoon: http://www.ndbc.noaa.gov/station_page.php?station=41049. The winds are already on the rise there, the pressure is falling, and the significant wave height is up to 10 feet and increasing rapidly.

Philippe hasn't been so fortunate. Still a 45kt tropical storm, it is battling relentless vertical shear, and will continue to do so for several more days.

In the plot below, you can see the track forecasts taking it generally westward over the next 5 days, and the shear forecast highlighting an unpleasant week for Philippe. The official intensity forecast is in line with the statistical models on that plot (LGEM, DSHP, SPC3), and weakens the storm to a Depression by the end of the weekend.

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Fourth hurricane of the season

2011-09-29T14:39:00.001-06:00

At 21Z today, Ophelia was upgraded to a 65kt hurricane, the 4th of the season. This is still a record low number of hurricanes for having 16 named storms though. Looking back through the records, any season with 16+ named storms had at least 7 hurricanes.

The storm intensity guidance is from satellite estimates, since there aren't any aircraft in it, and it's not too close to any buoys. The central pressure is down to 987mb, with a forecast for additional strengthening over the next couple of days.

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Ophelia nearly a hurricane

2011-09-29T11:24:00.000-06:00

The easterly wave that exited the African coast on September 16 became TS Ophelia on Sep 21, then on the 25th was so weak that it wasn't even classified as a Depression. A couple days later, it regained Depression status, then yesterday it regained TS status, and today, after this tremendous comeback, it is almost the season's 4th hurricane! The images on this page allow you to easily track the appearance of this system over the past week: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/hovmoller/epac_carib1/

At 15Z this morning, Ophelia is a 60kt TS with 991mb central pressure. The microwave image below shows quite clearly that the storm has formed an eyewall, though the eye hasn't cleared out yet in infrared imagery.

The forecast is for some additional strengthening over the next couple of days as it heads north toward Bermuda. Then as it comes under the influence of a mid-latitude trough, the shear will increase, and as it enters the north-central Atlantic, the SSTs will decrease. Together, these effects will transform Ophelia into an extratropical cyclone within 4-5 days.

Moving on to Philippe... not much has changed. The storm is still embedded in a strong vertical shear environment, so the deep convection associated with the Low is displaced completely to the northeast of the surface circulation. At 15Z, the intensity estimate is 40kts and 1005mb... located about 1240 miles west of the Cape Verde islands.

The forecast is looking more interesting with time. A large-scale ridge is expected to move back over the central Atlantic, which would steer eastern Atlantic systems more to the west (the current trough in place has been pulling everything north). So despite the shear remaining fairly high during the period, the SSTs will at least be warm, and Philippe should be several degrees north of the Leeward Islands by the middle of next week.

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Ophelia makes a comeback, and Philippe struggles

2011-09-28T09:03:00.000-06:00

Since my last update on Monday, the remnants of Ophelia made a comeback. The vertical shear decreased a bit more than expected, and the storm was surprisingly quick to take advantage of the improved environment. It was upgraded to a Depression on Tuesday afternoon, and at 15Z this morning was upgraded again back to a Tropical Storm. Though it's still in nearly 20kts of shear, convection has remained much closer to the center than it was a couple of days ago. The latest intensity is 45kts and 1002mb.

You can view a radar loop of Ophelia from Guadeloupe at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/ophelia11/Ophelia_27-28Sep11.gif
Although it's currently meandering very slowly, it is forecast to accelerate to the north within a day, and like Maria, reach hurricane intensity for the first time thanks to baroclinic enhancement as it interacts with a mid-latitude trough. It should remain safely east of Bermuda when it passes by there on Saturday.

TS Philippe has a very similar appearance on satellite, but is a little weaker: a 35kt storm with 1006mb central pressure. The forecast varies greatly depending on whether you're looking at a statistical models or dynamical models. The official forecast agrees with the statistical models (LGEM, SHIPS, etc), by the way.

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Ophelia dissipates and Philippe forms

2011-09-26T10:19:00.002-06:00

Since my last update on Friday, Ophelia succumbed to the strong vertical shear and lost its tropical characteristics... namely, co-located persistent deep convection. The final advisory was written on Sunday afternoon, and it's currently being tracked as a remnant low with a slight chance of regeneration... located northeast of the Leeward Islands.

Also since Friday, the disturbance I mentioned in the far eastern Atlantic was upgraded to TD17 shortly after my update was sent out, then upgraded again to TS Philippe on Saturday afternoon. Philippe is the 16th named storm of the season... climatologically we would have just 8 named storms by this date. Amazingly, 2011 is on par with the hyperactive 2005 season (in 2005 we were at the 17th named storm by this date). As of this morning at 15Z, Philippe is a 50kt tropical storm located 600 miles west of the Cape Verde islands.

Philippe is also struggling with fairly strong vertical shear, as well as moderate SSTs (27C)... it should continue to maintain TS intensity as it recurves to the north in the coming days. The 500mb chart below shows a deep trough in the central Atlantic that is responsible for recurving this storm so quickly.

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Ophelia still struggling, new disturbance in far eastern Atlantic

2011-09-23T11:39:00.000-06:00

Over the past couple of days since my last update, not much has changed with TS Ophelia... the storm reached 55kt intensity, but has been plagued by very strong vertical shear. At 15Z today, it's down to a generous 35kts, with a forecast for additional weakening. In the satellite image below, you can see the exposed surface circulation near 15N 53W with a convective blowup to the north, but the bulk of the convection displaced far to the east. It's in about 20-25kts of southwesterly shear, and over the next 5 days, that is not expected to let up at all.

As you can see from the plot below, the models have backed off significantly on their intensity forecasts, and their high-shear environments all agree in the near term (GFS is quite a bit larger several days out, and that is the model that the DSHP and LGEM intensity models are based on).

Elsewhere, a fresh easterly wave exited the African coast yesterday and is presently south of the Cape Verde islands. This wave was born over the Ethiopian Highlands 8 days ago and has a history over the past 3-4 days of being convectively active. It appears likely that this system will be our next named storm: Philippe.

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TS Ophelia forms

2011-09-21T10:58:00.000-06:00

[This is the second and final update being sent to both the old and new mailing lists. Check to make sure you are receiving this with tropatlan@googlegroups.com in the "To" field. There are still quite a few people who have not migrated to the new list. If you need any assistance or have questions, please ask.]

The easterly wave that exited the African coast on Sep 16 was upgraded to Tropical Storm Ophelia at 03Z today. This is the 15th named storm of the season... climatologically by this date we would have just 7 named storms!

A fairly recent ASCAT overpass from 12Z shows a nice closed surface circulation with TS-force winds in the north half (ASCAT is a satellite-based microwave scatterometer which is able to retrieve surface wind speed and direction over water by detecting the surface roughness caused by winds disturbing the ocean's surface).

At 15Z this morning, Ophelia's intensity was estimated at 50kts with a minimum central pressure of 1005mb. It's located about 1100 miles east of the Lesser Antilles and tracking W at 14kts. It's being sheared, so the intensification has likely leveled off and it will continue to the W-WNW over the next several days as a TS. The official forecast places it just north of Puerto Rico in 5 days as a TS, and the majority of model guidance supports that scenario.

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New disturbance in eastern Atlantic

2011-09-19T13:45:00.000-06:00

[This message is the first being sent to both the old and the new email lists. I apologize for duplicate mailings, but I want to give everyone a chance to migrate and accept the invitation to the new Google Groups list. If you have not yet accepted the invitation I sent on Friday (there is a link to click in that message... the subject was "Google Groups Invitation: Tropical Atlantic Update"), you will stop receiving these updates once I discontinue the old list. The old distribution address was tropical@atmos.colostate.edu, and the new address is tropatlan@googlegroups.com. Please check with me if you have any questions or problems!]

Over the past week or so, 3 easterly waves left the African coast. But rather than making their way westward one after the other, they have begun to accumulate in a weak-steering region between 35-40W. There's some evidence of this if you look at the time series of infrared images over the deep tropics: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/hovmoller/atlantic/ In this view, the newest image is on top, and then you look back 12 hours every slice as you go down the page. This allows you to track persistent features (such as African easterly waves) for many days simply by looking at their convective signature! The visible satellite below shows the appearance of this disturbance as of this writing, with the surface center location marked by a red dot. The estimated intensity is 25kts and 1008mb, and it's very close to becoming a Depression (TD16). The next name on the list is Ophelia.

The plot below shows the past, present, and forecast intensity, track, shear, SST, and mid-level humidity. The important thing to take away from it is that significant development of this is not expected in the near future, mostly because the vertical shear will be rather high.

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Maria becomes season's third hurricane

2011-09-16T12:08:00.001-06:00

After 9 days in the deep tropics since it was first classified as a Depression, Maria was upgraded to a hurricane at 21Z yesterday... making it the 3rd of the season (after Irene and Katia). The extratropical transition is underway, and though it won't be classified as a hurricane much longer, it will remain a powerful extratropical cyclone with hurricane-force winds as it heads across the northern Atlantic toward Greenland and Iceland. As of 15Z today, it is a 65kt hurricane with a 983mb central pressure... located just offshore of Newfoundland and racing NE at 45kts.

You can follow Maria on radar (until it zips out of view anyway) at http://www.weatheroffice.gc.ca/radar/index_e.html?id=WTP

Also, we've gotten lucky again with a buoy... Buoy 44251 is presently just 34 miles west of the center, and is reporting the following as of this writing (you can follow up later and see the full trace at http://www.ndbc.noaa.gov/station_page.php?station=44251):

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Maria strengthens slightly

2011-09-14T08:52:00.000-06:00

Over the past two days since my last update, Maria has barely maintained intensity in the 45-50kt range, due to the strong vertical shear. Since Tuesday morning, the central pressure fell 5 mb... the only sign of vigor it has shown lately. At 15Z today, the intensity is 50kts and 1001mb. The low-level center (marked by the red dot on the image below) is still on the far fringe of the deep convection in the face of 15kt shear.

At about 06Z today, Maria passed just 20 miles west of Buoy 41046, and the buoy reported a surface pressure of 1004.5mb, along with sustained winds of 33kts, gusts to 43kts, and a significant wave height of 18 feet. The wind and pressure trace also indicates a fairly weakly-organized core, with the pressure minimum coinciding with a tiny wind minimum and surrounded closely by wind maxima. Quite a different look than the plot I showed from Katia's passage over Buoy 41048 six days ago!

Much like Katia, Maria is about to encounter a strong mid-latitude trough... and with that comes some baroclinic enhancement and an eventual extratropical transition. So, in the coming couple of days, the storm could approach hurricane intensity even as the shear skyrockets and the SSTs plummet. It will recurve between Bermuda and the US, with the closest approach to Bermuda occurring Thursday morning.

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Nate makes landfall, Maria still a TS

2011-09-12T09:10:00.001-06:00

Nate never made it to a hurricane, but that fits with the rest of the season.... only 2 of the 14 named storms have become hurricanes. That's just 14% compared to the climatological 50-60%. However, in terms of named storms, 2011 is just 1 behind the mega-season of 2005... by this date in 2005, we were on the 15th storm, and this year, we're on the 14th. Tropical Storm Nate made landfall at about 1730Z on Sunday by Poza Rica. The satellite image below is from the approximate time of landfall, and the full radar loop from Alvarado can be found here: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/radar/index.html#nate11

Maria has been battling relentless vertical shear. Now up to 30kts, the shear has displaced Maria's deep convection far to the east of the low-level circulation, as you can see clearly in the visible satellite image below (the surface center is near 21.7N 67.2W in this image).

The intensity has been holding at 50kts for the past 30 hours, and the track has also been steady at WNW at around 8kts. It is forecast to begin recurving to the north shortly, well before reaching the US, then pass just west of Bermuda on Wednesday night, then zip off into the north-central Atlantic. It's still a possibility that Maria will reach hurricane status in 48-60 hours when it briefly could be exposed to less shear, and when it begins to experience baroclinic enhancement.

Elsewhere, a large easterly wave has just exited the African coast today, and has had a history of being very active since it formed over the Ethiopian Highlands on Sep 4. It is not organized at all yet, but the surface pressure in coastal African stations fell to about 1011mb as it passed over, and is the next feature to keep an eye on over the coming week.

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Katia, Maria, and Nate still making waves

2011-09-09T09:44:00.000-06:00

Katia remains a strong Category 1 hurricane with 75kt winds as it recurves into the north central Atlantic. It's over 26C water, in about 20kts of vertical shear, and is about to begin its extratropical transition (ET). This will be a major storm for the UK early next week.

The baroclinic enhancement that commonly occurs with ET can keep the intensity high even amidst what we typically think of as hostile conditions. In the next 24h, the SST will plummet to 18C and the shear will increase to about 45kts, but the storm could still pack hurricane-force winds. ET involves losing the circular symmetric structure and becoming more frontal in nature (which implies the cyclone tilts with height rather than being vertically stacked), while at the same time transitioning from a warm-core system to a cold-core system (which implies the strongest winds move outward and upward). Tropical cyclones have their strongest winds at the surface and close to the center, while extratropical cyclones have their strongest winds aloft and quite removed from the center.

Maria has regained a lot of deep convection, and the intensity as of 15Z today is 40kts, with a forecast for VERY slow intensification over the next 5 days as it heads WNW toward the Bahamas. Tropical Storm warnings cover the Leeward Islands and Puerto Rico (http://www.nhc.noaa.gov/storm_graphics/AT14/refresh/AL1411W5+gif/145220W_sm.gif). The vast majority of forecast models now indicate that Maria will follow a track similar to Katia, so as of now, it appears that the US east coast could be spared another rainmaker.

Nate is organizing and wrapping up, but part of what it's wrapping up is the very dry air from Mexico and the northwestern Gulf. The entrainment of dry air into the system has limited its intensification, but it's still a 55kt tropical storm. It is forecast to reach hurricane status by tomorrow morning as it crawls slowly westward toward the northern Veracruz coastline in Mexico. There are hurricane and tropical storm watches/warnings around the Bay of Campeche's perimeter: http://www.nhc.noaa.gov/storm_graphics/AT15/refresh/AL1511W5+gif/143800W_sm.gif

Finally, it's worth noting that we are in the peak of the season now... Sept 10 is climatologically when we have the most activity in the basin: http://www.nhc.noaa.gov/climo/images/peakofseason.gif

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Katia turns north, Maria struggles, and Nate strengthens

2011-09-08T09:32:00.000-06:00

Hurricane Katia strengthened slightly to 80kts as of 15Z today, and did indeed pass over Buoy 41048 as expected -- the center of the eye was actually 34 miles west of the buoy at closest approach at 09Z. It has also completed its turn to the north, and over the next few days will turn northeast and out into the north-central Atlantic graveyard. However, it's only a graveyard for tropical cyclones... it will still be an extremely potent and dangerous extratropical cyclone as it heads for the UK early next week.

Peak observations from the [un]lucky buoy include a 976mb pressure, 40-foot significant wave height, 68kt sustained winds, and 93kt wind gusts. The SST dropped from its pre-storm value of 28.4C to a low of 25.1C!
http://www.ndbc.noaa.gov/station_page.php?station=41048

Maria is still a 40kt tropical storm, but looks quite anemic this morning... a sign that shear and dry air are nudging their way into the vortex.

The plot below is the initial condition from HWRF's 06Z run... it's an along-shear cross-section of wind speed and relative humidity. You can clearly see the asymmetry in the wind field (shaded), as well as the low RH values (contours) being forced into the system by the strong shear. The official forecast brings Maria over the central Bahamas in 5 days as a strong tropical storm. Given this track, the southeast and east coast of the US should be very alert... this is nearly a copy of Irene's track.

Tropical Storm Nate is at 45kts, and still virtually stationary. It's forecast to slowly intensify to a hurricane on Saturday as it begins to crawl to the northwest toward the US/Mexico border next week. You can view full-resolution visible images of Nate at http://rammb.cira.colostate.edu/ramsdis/online/loop_640.asp?product=tropical_ge_1km_center_relative_vis_floater

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Katia, Maria, and Nate keeping the basin active

2011-09-07T17:25:00.001-06:00

Hurricane Katia has not changed too much since my update this morning, but I wanted to highlight once again the buoy that it is going to pass over. It's a special occasion when a hurricane eye manages to pass directly over a tiny stationary buoy in the middle of the ocean. And today, Buoy 41048 is that lucky one. As of this writing, the buoy is 110 nautical miles NW of Katia's eye, and Katia is moving NW at 9kts (and a knot is a nautical mile per hour)... so that's about 12 hours until closest approach. Already though, huge waves over 30' tall are rocking the buoy ("significant wave height" is defined as the average of the highest 1/3 of the waves), and wind gusts up to 54kts have been measured. You can view current data and additional plots at http://www.ndbc.noaa.gov/station_page.php?station=41048

Maria is still a tropical storm, but I hunted through some historical tracks that matched Maria in terms of location, month, and intensity. One very noteworthy result stuck out: Hurricane Hugo. The track plot below shows Hugo's track, and the gray circle is a 100-mile circle around Maria's current location. Hugo was located where Maria is now on September 13, 1989. This of course doesn't mean that Maria will be a Hugo, but it's certainly worth paying close attention to history.

Last but not least, the disturbance in the Bay of Campeche was upgraded to Tropical Storm Nate, the 14th named storm of the season, based on aircraft reconnaissance. The intensity is 40kts and 1004mb, and it's basically stationary. In such weak steering flow, a track forecast is extremely difficult to make, for both models and humans. Models are all over the place with it, and justifiably so... but the official NHC forecast keeps it stationary for another 2 days, then ever so slowly tracks it northwest toward Mexico. All of this time over the warm Gulf of Mexico should allow for some intensification, probably becoming the season's 3rd hurricane by the weekend.

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Katia weakens, Maria forms

2011-09-07T10:21:00.003-06:00

Katia continues to lose its organization in the face of increasing vertical shear. At 15Z today, the intensity is down to 75kts, and the forecast is for a very gradual weakening and loss of tropical characteristics. It is going to pass over a buoy located near 32N 70W later today... you can view observations (wave height, wind, pressure, etc) at http://www.ndbc.noaa.gov/station_page.php?station=41048 The infrared image below shows Katia, then Bermuda is the yellow speck near 32N 65W, and the buoy I mentioned is shown by the red dot.

Shortly after I sent out yesterday's update, the easterly wave that was near 35W was upgraded to TD14. Then 18 hours later (15Z today), it was upgraded to Tropical Storm Maria, the 13th named storm of the season. Maria's estimated intensity is 45kts with a 1003mb central pressure. It's located at 13N 42W (about 1300 miles east of the Lesser Antilles) and cruising westward at 20kts. The environment that it's in is only marginal for intensification... the SST is a healthy 28C, but the vertical shear is 12kts and increasing. So, it will probably just slowly strengthen over the next several days, while tracking WNW toward the northern Leeward Islands. This is a storm to keep a very close eye on if you're on the US coast; though at this point it's too early to say if it's heading for the Gulf coast or the east coast.

The trailing end of a front extending from the northeast US through Florida and into the Gulf of Mexico has been showing signs of organization. The front ends in the Bay of Campeche, and the pressures are dropping in the area... with this disturbance at approximately 1007mb. The 06Z surface analysis shown below illustrates the position of the front, and the terminal Low in the Bay of Campeche. Also note the Low in western VA/NC associated with the remnants of TS Lee.

The steering flow in this area is very weak, so it's not going anywhere in a hurry. It's also surrounded by dry air, so even if it does make to a TD or TS, it shouldn't get much stronger. If named, the next name on the list is Nate.

Please visit my tropical Atlantic headquarters.

Katia becomes season's 2nd major hurricane

2011-09-06T09:39:00.000-06:00

The intensification trend I mentioned in Sunday's update did indeed continue, and on Monday at 21Z, Katia was upgraded to a Category 3 storm with 100kt sustained winds... then just six hours later, was upgraded again to a Category 4 storm with 115kt winds. In the 18-hour period from 09Z on Monday through 03Z today, the pressure fell 26mb and the winds increased by 30kts.
As of 15Z today, the intensity is down a little to 105kts with a central pressure of 954mb.

The tiny yellow speck you see on that image near 32N 65W is Bermuda... and they now have a tropical storm watch in effect. Models are now in excellent agreement on the track, and they indicate a recurvature by about 72W, safely off the US east coast, and safely west of Bermuda (though Bermuda could certainly feel some outer effects like tropical storm force winds and very large ocean swells).
The shear is also expected to increase again, and the mid-level relative humidity is quite low, so it appears that Katia will be on a steady weakening trend now until it ends up in the TC graveyard of the north central Atlantic.

The easterly wave that exited the African coast on Sep 2 (AL95) is now near 35W, or almost 1800 miles east of the Lesser Antilles. It continues to show signs of organization, and will likely be upgraded to TD14 or even TS Maria within the next 24-48 hours. The environment it's moving into isn't the best, so if it does develop, it should be slow to intensify for the next several days. It is very far from land, but it will be something to keep a close eye on simply because of its location and potential track (the southeast US is about 11 days away).

Please visit my tropical Atlantic headquarters.

Katia rapidly intensifies, Lee makes landfall

2011-09-04T09:00:00.001-06:00

Not much changed since my last update on Friday... Katia has been hovering on the 60-65kt mark, which also means switching between TS and hurricane each time (fairly big name shift for a very minor change in wind speed). The vertical shear has been much slower to let up than forecast (except for the GFDL model, which did see this extended period of high shear, but it was an outlier), and as a result, Katia did not intensify as forecast... but also didn't weaken much either. However, conditions have improved over the past few hours, and the storm was quick to respond in a big way. The intensisty as of 15Z today has skyrocketed up to 85kts with a central pressure of 966mb, and a open, clear eye is forming... it was a 60kt TS with a pressure of 992mb six hours ago! The center is about 375 miles northeast of the northern Leeward Islands. The forecast is still for additional intensification, and for a continued northwest track; it's looking quite likely now that Katia will recurve prior to reaching the US east coast, AND stay to the west of Bermuda.

Shortly after my update on Friday, TD13 was upgraded to TS Lee based on aircraft recon. Since then, it did not intensify much, but as expected, remained a large amorphous rainmaker, crawling along at 2-5kts. It made landfall about 50 miles west of Morgan City with 40kt sustained winds. But more importantly, the rain keeps falling.

There has already been up to a foot of rain across the southern coast, from LA to AL, over the last 3 days. More will come today and tomorrow. Lee should still be over southern LA for at least another day, then begin accelerating to the northeast ahead of a mid-latitude trough... tracking over MS, AL, and TN over the next 3-4 days. The graphic below shows the estimated rainfall totals over the past 4 days in the region:

Please visit my tropical Atlantic headquarters.

Katia hanging on, TD13 forms in Gulf

2011-09-02T10:06:00.001-06:00

Katia actually went against model guidance again and weakened a bit to a strong tropical storm yesterday afternoon, but has since reintensified to a minimal hurricane (65kts, 991mb). The vertical shear was quite a bit stronger than forecast, and it definitely took a toll on the storm. However, with shear dropping from 20kts to 10kts over the next couple of days, Katia should be able to resume the previous strengthening trend.

The official forecast calls for gradual intensification to 100kts (Cat 3) over the next 5 days as it heads WNW... with a 5-day (Wednesday) position located about 500 miles north of Puerto Rico. The long-term future is still too uncertain as to whether it will recurve before reaching the US east coast or not, but extended-range models generally indicate a safe recurvature. Certainly something to keep a very close eye on anywhere along the east coast though.

The disturbance that I first mentioned on Tuesday has been upgraded to TD13, and is not far from becoming Tropical Storm Lee. This disturbance was way back by the Lesser Antilles on Aug 25, so it's been "on the radar" for a week now. It is organizing very quickly now that the vertical shear is relaxing -- from 25kts to 5kts over the next 24 hours. The intensity is 30kts, it's centered just 190 miles southwest of New Orleans, it's nearly stationary, and the outer rainbands are already onshore.

Tropical Storm warnings are up for the entire LA and MS coast... the latest forecast track, watches, and warnings can always be found at http://www.nhc.noaa.gov/storm_graphics/AT13/refresh/AL1311W5+gif/145613W_sm.gif

The 5-day accumulated precipitation forecast from HPC is still very ominous for the southeast, with 1-2 feet of rain possible over southern LA and MS. You can watch the regional radar loop showing the extent of the rainfall at http://radar.weather.gov/Conus/southmissvly_loop.php

This flooding rain will be combined with perhaps multiple days of tropical storm force winds, and I wouldn't be surprised at all if some evacuations were ordered for New Orleans, Biloxi, Mobile, Pensacola, and other urban flood-prone cities in the area (as well as offshore oil rigs). If you or someone you know is down there, keep a close eye and ear to the local tv and radio stations this weekend.

Finally, the circulation that was north of Bermuda yesterday has not moved much at all, but is actually even more sheared than it was... making any development unlikely. What convection there is in association with this system is displaced far to the northeast, and while the SSTs are fairly high now (28C), they will plummet to 22C within a day as it moves to the northeast.

Please visit my tropical Atlantic headquarters.

Katia now a hurricane, Gulf disturbance organizing

2011-09-01T09:30:00.003-06:00

Welcome to September, by far the busiest month of the Atlantic hurricane season!

As of this morning, Katia was upgraded to a hurricane (second of the season) with 65kt sustained winds and a 987mb central pressure.

It's located about 850 miles east of the Lesser Antilles and heading W at 16kts. This westward motion was not anticipated... models have been in excellent agreement that the WNW or even NW track would persist. This could suggest that the more southern models among the guidance package could be on the right track. The models also collectively suggest a continued gradual intensification (shear is an inhibiting factor, but not strong enough to be too detrimental).

The disturbance that was near the northern Yucatan peninsula yesterday is now well into the Gulf (AL93). It has persistent deep convection, but is in about 20kts of vertical shear. This is forecast to let up over the next couple of days, perhaps allowing this to organize. The next name on the list is Lee.

The current NW heading should also come to a halt as it encounters a region with little or no steering flow, leaving it to drift very slowly just off the northern Gulf coast... possibly bringing a major flooding threat with it. The graphic below from NOAA/HPC shows the forecast 5-day rainfall totals. Yes, that's an 18.9" bullseye over southern LA. Whether this storm becomes a TS or hurricane seems like a minor point compared to the flooding potential.

There is also a small and highly-sheared circulation north of Bermuda that bears watching (AL94).

Please visit my tropical Atlantic headquarters.

Katia intensifies, could become hurricane later today

2011-08-31T09:16:00.000-06:00

Katia is still a tropical storm, but the central pressure has fallen 9mb in the past 24 hours... certainly not rapid by any measure, but on a decidedly strengthening trend. The maximum sustained winds are estimated at 55kts as of the 15Z advisory, and additional (substantial) intensification is expected.

Forecast models are in excellent agreement on a continued WNW track for the next 5 days, which brings it near the northern Leeward Islands. Beyond that, there is some divergence... with the majority recurving it well off the US east coast (perhaps bad news for Bermuda) and a minority bringing it very close to the US east coast. There is plenty of time to refine the forecast track before it's a thread to any land.

The disturbance I mentioned in the western Caribbean continues to simmer, now near the northern tip of the Yucatan peninsula.

Many models slowly develop this as it heads NW into the Gulf of Mexico, then by this weekend into next week, have it stall off the TX/LA coast... perhaps strengthening as it sits there. Definitely something to keep an eye on. The image below shows the total precipitable water (TPW... the total amount of water in an atmospheric column if it all condensed out), and the large envelope of high values surrounding this disturbance. An environment of very moist air is healthy for tropical cyclones, both young and old.

Please visit my tropical Atlantic headquarters.

Tropical Storm Katia forms in far eastern Atlantic

2011-08-30T09:07:00.001-06:00

At 09Z today (5am EDT), TD12 was upgraded to TS Katia, the 11th named storm of the season, based on satellite presentation. The 15Z intensity estimate is 40kts, with a 1003mb central pressure. It's centered near 12N 34W, or roughly 1800 miles east of the Lesser Antilles, and heading WNW at 16kts.

Katia is forecast to intensify fairly quickly, reaching Category 3 status within 5 days as it approaches the Leeward Islands. The WNW motion is expected to continue, bringing it near 20N 60W by Sunday morning. In 8-10 days from now (late next week), it could be on a similar track to Irene or perhaps further east over the ocean, so it will of course be watched very closely. The graphic below shows the forecast intensity and track of the storm, as well as the vertical shear, SST, and RH in the storm's environment (left of the vertical lines is in the past, right of the vertical lines is the forecast... from the various models listed in the legends). You can find the latest version (and full size) of this at http://rammb.cira.colostate.edu/products/tc_realtime/storm_model_data.asp?storm_identifier=AL122011

Climatologically by this date, we would have 4 named storms, 2 hurricanes, and 0 major hurricanes. We are currently at 11, 1, and 1.

Elsewhere, there is a very slow-moving easterly wave festering in the western Caribbean that warrants attention. Many models favor this for development, with a VERY gradual track toward the TX/LA coast; possible Gulf coast landfall in the middle of next week... IF it develops.

Please visit my tropical Atlantic headquarters.

Irene and Jose dissipate, TD12 forms

2011-08-29T12:06:00.000-06:00

The final advisory was written on Irene at 03Z today, located north of Maine and still producing heavy rain in eastern Canada. As of this writing, Irene is blamed for at least 24 deaths, tens of billions of dollars in property damage, major disruptions to the nation's transportation network, and about 3 million people without electricity. The radar/raingauge precip totals during Irene's passage are shown below. There are values approaching 20" near Albany NY, Suffolk VA, and Greenville NC, but very heavy totals from NC into northern New England resulted in widespread flooding. The governor of Vermont summed up the weekend for many areas: "We prepared for the worst and hoped for the best and unfortunately got delivered the worst".

All of the radar loops that I've made for Irene can be found at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/ (News & Updates section, or in the CSU Atmospheric Science section). This includes coverage from San Juan PR, Miami FL, Morehead City NC, Dover DE, and New York City NY.

The odds of the name Irene being retired are high, which would make it the 7th "I" storm in the past 11 years to be retired (joined by Iris, Isidore, Isabel, Ivan, Ike, Igor). Quite unusual!

Short-lived TS Jose has already dissipated after being a named storm just a day. It formed southwest of Bermuda and the remnants are now north of Bermuda.

The easterly wave that I mentioned yesterday is now near 28W and was upgraded to TD12 at 09Z this morning. The environment should improve in the coming days, mostly in the form of decreased vertical shear. The majority of models are quite aggressive in developing this, and it will likely become our next tropical storm and hurricane: Katia.

One additional tidbit: today is the 6th anniversary of Katrina's final landfall in LA. The next name on this season's list, Katia, is the replacement name after Katrina was retired.

Please visit my tropical Atlantic headquarters.

Irene near NYC, Jose near Bermuda, new wave near Cape Verdes

2011-08-28T08:21:00.000-06:00

Since yesterday, Irene has been downgraded to a tropical storm with 65kt winds, and the center has just passed over New York City. The rain shield is almost entirely on the north half of the storm, so from southern NY up into Canada there is widespread heavy rain, but south of there, coverage is pretty minimal. Without going into immense detail from all possible locations, Irene has already been blamed for 10 deaths, and extensive coastal erosion and flooding in much of mid-northern Atlantic states. It will be easier to summarize the rainfall amounts once it's done raining. Here is a composite radar image showing the extensive rainfall as of 10am EDT this morning:

There is extensive flooding in Lower Manhattan, Philadelphia, the list goes on. And, for those of you without power, or with a flooded basement/business, etc, just remember that this hurricane was a blessing, according to Glenn Beck. (http://religion.blogs.cnn.com/2011/08/27/glenn-beck-hurricane-irene-is-a-blessing/) Sorry, couldn't resist tossing that in. If anyone cares to share stories or photos from Irene, I'd be happy to share them on here for you!

For some additional tidbits on Irene, check out this NYT article: http://www.nytimes.com/2011/08/28/us/28hurricane-irene.html

Earlier this morning Tropical Storm Jose formed on Bermuda's doorstep, prompting short-fuse warnings. The intensity is 35kts, but is forecast to weaken. It's located 100 miles southwest of Bermuda and heading north at 14kts. This is a small weak system, but you can see the circulation on Bermuda's radar: http://www.weather.bm/radarLarge.asp

Elsewhere, another vigorous easterly wave exited the African coast yesterday (early on the 27th). It's centered near 22W, and forecast to develop fairly quickly as it heads WNW over the next several days. It's no immediate threat to anyone, and the next name on the list is Katia (replaces Katrina from 6 years ago).

Please visit my tropical Atlantic headquarters.

Irene makes first US landfall in NC

2011-08-27T09:25:00.000-06:00

At about 12Z today (8am EDT), Irene made landfall near Cape Lookout, NC as a Cat 1 hurricane. The radar image from the approximate time of landfall is shown here.

The northeast is still in the crosshairs, and although Irene is weakening, that will only minimally affect the storm surge and not affect the rainfall... the category rating is only for wind, not water (though a stronger storm will generally generate a larger storm surge). The Chesapeake Bay, Delaware Bay, Long Island Sound, and all inlets, bays, and sounds along the northeast coast should still be ready for some major flooding. The latest storm surge model output for the northeast metro areas is shown below:

And, in addition to this, the entire northeast can expect huge amounts of rain in the next 36 hours. The graphic shown here is the forecast accumulated rainfall over the next 3 days (in inches). This will be a very historic storm, even if it's only a tropical storm by the time it reaches New York! As of this update, the rain is already beginning to fall as far north as CT and RI, including VA, PA, DE, MD, NY, NJ. As the storm progresses, you will be able to find current and additional long radar loops at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/

Please visit my tropical Atlantic headquarters.

Irene forcing evacuations in nine states

2011-08-26T16:47:00.000-06:00

Hurricane Irene has weakened a bit more this afternoon in terms of maximum sustained wind speed in the core, but as I mentioned earlier, the main threats are the storm surge and the rain... the exact intensity should not be the focus when it comes to preparations and evacuations. At 21Z today, the maximum sustained winds were 85kts, making it a Cat 2 storm. It is located 265 miles south of Cape Hatteras NC and moving N at 12kts.

I first mentioned this disturbance on Aug 16, one day after it exited the African coast. Now, 10 days later, it's getting a bit more attention! Here is a satellite image from Aug 15 showing pre-Harvey approaching the Lesser Antilles and pre-Irene just west of Africa.

And here is Irene as of this writing. What a difference 11 days makes!

Tropical storm force winds and outer rainbands are already ashore in NC, where landfall isn't expected until early Saturday morning. The radar loop covering the landfall can be found here: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/ (in the News & Updates section)
For some perspective on size, if you placed Irene's circulation over the continental US, it would cover Florida up to Pennsylvania, and from North Carolina to Oklahoma. This is a large storm.

There are evacuations in coastal areas from NC up to MA, and wisely so. Even if Irene continues to weaken, the storm surge and rainfall will be extremely destructive. The storm surge is forecast to reach 8' in parts of the Chesapeake Bay, up to 6' in parts of the Delaware Bay, and 3-6' in the NJ/NY area. The latest storm surge forecast for the NJ/NY area is shown below. For the first time in history, New York City is shutting down its mass transit systems and evacuating low-lying portions of the city (300,000 people so far).

Looking back, I was able to find just 12 hurricanes in the past 160 years that had comparable tracks to Irene, many of them notable and infamous. These include Floyd (1999), Bob (1991), Gloria (1985), Belle (1976), Donna (1960), Carol (1954), Edna (1954), and 5 from earlier years when storms weren't given names (1944, 1894, 1879, 1861, and 1858). The plot below shows the east-central portion of the coast with these storms' tracks overlaid. So Irene will be added to this list and be remembered just as these are.

Please visit my tropical Atlantic headquarters.

All eyes on Irene as it heads toward US coast

2011-08-26T09:28:00.000-06:00

As of the latest advisory, Irene is heading N at 12kts with 90kt sustained winds. It's about 330 miles S of Cape Hatteras NC. The latest forecast track, watches, and warnings can be found at http://www.nhc.noaa.gov/storm_graphics/AT09/refresh/AL0911W+gif/092739W_sm.gif The track is very ominous, and one of the worst-case scenarios for the entire northeast coast. It's been 6 years since the US has experienced a major hurricane landfall, and that was Wilma when it hit just south of Naples FL with 105kt winds. The last non-major (Cat 1-2) US hurricane landfalls occurred in 2008: Dolly, Gustav, and Ike (TX, LA, TX).

The first and strongest US landfall is expected in the early morning hours on Saturday, near Morehead City, NC, as a Category 2 (90kt) storm. In addition to the powerful winds gusting up to 125mph, the storm surge will be quite high... up to 9' in surge-prone areas like Pamlico Sound. Keep in mind that large violent waves are on top of that storm surge, and both are on top of the normal tides.

A long-range radar loop from Morehead City can be found here:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/irene11/Irene_26-27Aug11_MHXlong.gif
and a short-range radar loop can be found here:
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/irene11/Irene_25-26Aug11_MHXshort.gif
Also, the exact time and location of landfall is almost irrelevant for a storm this large... the effects of the hurricane will be felt far from the center and for at least 12 hours before the eye crosses the coastline.

Further north and a day later, Irene will be just off of the NJ coast, and creating a large storm surge in the Chesapeake and Delaware Bays as well as along the ocean. Norfolk VA is in a very sensitive area, and can expect a 6-7' surge. It could still be a powerful Category 1 storm at that time, so wind gusts up to 120mph could affect coastal VA, MD, DE, and NJ. There is still a lot of concern for New York City, where low-lying parts of the city exposed to water are home to large numbers of people. Again, the evacuation map for NYC can be found here: http://www.nyc.gov/html/oem/downloads/pdf/hurricane_map_english.pdf

The image below shows what the latest forecast storm surge will be in the DE/MD/NJ/NY area:

Then on top of all of this is the rainfall. The image here shows the 5-day forecast accumulated rainfall totals (in inches). Many areas in the northeast have just gotten a lot of rain unrelated to the hurricane, so the ground is saturated prior to getting up to a foot of additional rain.

Please visit my tropical Atlantic headquarters.

Irene maintains Category 3 strength as it heads north

2011-08-25T16:07:00.000-06:00

Since this morning, Irene has maintained its intensity at 100kts, but the latest aircraft flight into the storm found a central pressure of 948mb, indicating that Irene is intensifying a bit.

I have a long radar loop from Miami showing Irene's eyewall and western rainbands at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/irene11/Irene_25-26Aug11_long.gif Sometime tomorrow, the storm will be in range of the Morehead City NC radar... and the radar loop will be available at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/irene11/Irene_26-27Aug11_MHXlong.gif

The latest forecast track, along with updated watches and warnings, is posted below. This track is only shown out to 3 days... the 5-day track of course extends further to the north.

Many coastal cities have already begun their evacuations and preparations. This is a very large and dangerous storm... do not be fooled by the exact category rating. The storm surge all along the east coast could be quite large, even up into bays and sounds, but certainly along the ocean. Mayor Bloomberg in New York City had the following to say about the situation:

"If the worst scenario is going to happen this weekend, we will activate other elements of our Coastal Storm Plan, including the possibility of evacuating of New Yorkers who live in low-lying areas that could be affected by such storm surges. That includes places such as Coney Island and Manhattan Beach in Brooklyn, Far Rockaway and Broad Channel in Queens, South Beach, Midland Beach, and other low-lying areas on Staten Island, and Battery Park City in Manhattan."

Please visit my tropical Atlantic headquarters.

Irene heading for US coast, TD10 forms

2011-08-25T10:20:00.000-06:00

Major Hurricane Irene is wrapping up its destructive tour of the Bahamas, and has its eye on the eastern US coast now. At 15Z today, the center of the storm was located very near Abaco Island in the Bahamas, and about 650 miles south of Cape Hatteras NC. The intensity is 100kts (Cat 3, 951mb) and the heading is NNW at 11kts. The structure got a little jumbled overnight, but appears to be reorganizing and intensifying now. This is a very large storm, with tropical storm force winds extending an average of 170 miles from the center, and hurricane force winds extending an average of 49 miles from the center. These will only increase with time.

The forecast track is becoming more and more certain thanks to large-scale troughs and ridges that are governing its motion in a very straightforward manner. Select model tracks are plotted on Jonathan Vigh's website: http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2011/al092011/track_late/aal09_2011082506_track_late.png
The official NHC forecast has a first landfall near Morehead City NC on Saturday morning as a Cat 3, then skimming along the coast, passing over the big northeast cities on Sunday morning-afternoon as a Cat 2 hurricane. Hurricane watches are already posted for much of NC, evacuation of the Outer Banks is underway, and a state of emergency has already been declared for coastal NC.

On this track, and at this intensity, and with its large size, Irene has the potential to cause a lot of trouble from NC to ME. "Trouble" refers to flooding rains, destructive winds, tornadoes, coastal erosion, and very large inundating storm surges. Some prior hurricanes with similar tracks hitting Long Island are quite infamous: Carol (1954), Donna (1960), Belle (1976), and Gloria (1985). The storm surge threat is very real with this storm, especially in big cities where many people are affected... Washington DC, Philadelphia, New York City, Boston, etc. In addition, very heavy rain can be expected all along the track; this map to the right shows the 5-day forecast accumulation totals. Given the enormous population and low elevation, New York City is a huge concern with a storm like this. Finally, if you live anywhere along the east coast from NC on up to ME, pay close attention to the local news, make preparations well ahead of time, and evacuate if told to so.

Of much less significance now, TD10 formed this morning from the easterly wave I mentioned yesterday. It is located at about 32W and is forecast track northwest and perhaps reach tropical storm intensity. This does not look like it will be a storm of any concern to anyone, but the next name on the list is Jose.

Please visit my tropical Atlantic headquarters.

Irene now a major hurricane

2011-08-24T10:45:00.000-06:00

Irene continues to track slowly over the Bahamas, and is intensifying. At 15Z today, it became the season's first major hurricane (Cat 3+), with an intensity of 100kts and a 956mb central pressure... that's a drop of 24mb in the past 24 hours. A current satellite image (as of this writing) shows a well-defined eye centered over Acklins Island in the Bahamas.

Irene has also begun to turn toward the northwest, and the current motion is northwest at 10kts. It is in an ideal environment for additional strengthening, and is forecast to reach 115kts (Cat 4) by Thursday morning. The official track brings Irene over the remainder of the Bahamas through Thursday night, then heading a bit more north... perhaps scraping by coastal NC on Saturday. More noteworthy however, is the track after that. If the current model runs and official forecast verify, Irene will hit Long Island NY and/or coastal New England -- and still as a powerful hurricane. One representative model run (HWRF) has an ominous forecast valid Sunday afternoon:

Aircraft are frequently flying into and around this storm to sample its structure and environment, hopefully resulting in accurate forecasts of intensity and track. You can find the latest track forecast, watches, and warnings at http://www.nhc.noaa.gov/storm_graphics/AT09/refresh/AL0911W5+gif/143914W_sm.gif

Elsewhere, a very strong easterly wave exited Africa on Aug 22 and is now centered near 12N 28W. It already has a vigorous mid-level circulation and is in a favorable environment for development. However, the present steering currents out there are expected to lift this system northwestward long before it's a threat to any land. If named, the next name is Jose.

Please visit my tropical Atlantic headquarters.

Irene heading for Bahamas and possibly US

2011-08-23T17:26:00.000-06:00

Since my last update on Friday (I apologize for the break during this interesting period... but it was vacation time), the easterly wave that was located far east of the Lesser Antilles has intensified dramatically. It became TS Irene on Saturday evening, crossed over the Leeward Islands, became the season's first hurricane on Monday morning as it crossed over Puerto Rico, and is now nearing Category 2 intensity as it begins to track over the eastern Bahamas.

The forecast is of course of great interest to the US, since storms in this location can easily hit the US coast (either by tracking westward and entering the Gulf of Mexico or by recurving and hitting the southeastern states). Models have been strongly trending toward an earlier recurvature, bringing any potential US landfall further and further northward along the coast. The figure below (from http://rammb.cira.colostate.edu/products/tc_realtime/) shows three models' track forecasts... thick lines for past location, very thin lines for past forecasts (shown only once daily), and medium lines for the most recent forecast. The feature to note is the older runs are consistently further west than the later runs.

The models are in good agreement for a NC landfall (or near miss offshore) on Saturday night, most likely as a Category 2-3 hurricane. Before that though, it is causing and will continue to cause substantial problems in the Bahamas (wind, heavy rain, large storm surge, etc). You can always find the latest official track forecast, watches, and warnings at http://www.nhc.noaa.gov/storm_graphics/AT09/refresh/AL0911W5+gif/205313W_sm.gif

The intensity at the latest advisory is 80kts with a forecast of 110kts in 3-4 days.

Please visit my tropical Atlantic headquarters.

TD8 nearing Belize, central and eastern Atlantic disturbances brewing

2011-08-19T10:39:00.000-06:00

At 03Z today, the easterly wave that we've been watching since it left Africa on Aug 10th was upgraded to TD8. It's cruising along the northern coast of Honduras, and on the verge of becoming a Tropical Storm. At 15Z, the intensity is 30kts and 1005mb. It is expected to intensify just slightly prior to landfall in Belize on Saturday evening, and if named, it would be Harvey. As time goes on (it's not in range as of this writing), you will be able to view a radar loop from Belize at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/harvey11/Harvey_19-20Aug11.gif

The easterly wave that exited Africa on the 15th (AL97) is now near 50W, or roughly 700 miles east of the Lesser Antilles, and tracking west at about 15kts. On its current track, it is expected to reach the Leeward Islands on Sunday morning, Puerto Rico on Monday morning, and then continuing toward Hispaniola, Cuba, and southern FL after that. The majority of models do develop this to a TS, and some to a Cat 1 hurricane... the amount of land it encounters will be a large factor in determining just how strong it can get.

Finally, another easterly wave exited Africa yesterday (AL98) and is centered near 20W now... not even to the Cape Verde islands yet. This vigorous wave was born over the Ethiopian Highlands back on Aug 12, traveled across Africa in one week, and is already showing signs of tropical development. It's too early to say much about the potential track of this, but models are indicating more of a NW heading than W by five days out.

Please visit my tropical Atlantic headquarters.

One disturbance nearing Central America, one in far eastern Atlantic

2011-08-18T11:36:00.000-06:00

The easterly wave that we've been watching since it left the African coast back on Aug 10th is now located just 200 miles due east of the Honduras/Nicaragua border. It is still not a Depression, but is visually very close (low-level winds appear to be circling in to it in all quadrants, and it has persistent centralized deep convection). An aircraft is flying through the system as I type this, which will determine if it has reached TD or TS status. It is forecast to continue its westward course, bringing it into Belize and the Yucatan Peninsula on Saturday... most likely as a Tropical Storm. The next name on the list is Harvey.

Elsewhere, the easterly wave that exited Africa on the 14th is now centered near 40W (about 900 miles west of the Cape Verde islands). This is a very large circulation, though lacking convection and organization.
Global forecast models indicate that this system will develop and be in the vicinity of Cuba and southern Florida by the middle of next week. It's a long way out, but worth keeping a close eye on. The following plot from Univ of Miami (http://www.rsmas.miami.edu/personal/smajumdar/predict/) shows the possible locations (from 20 members of the GEFS ensemble) of this disturbance next Thursday evening. Keep in mind that this is only showing an indication of track, not intensity, and from one model.

Please visit my tropical Atlantic headquarters.

Gert weakens, disturbance in Caribbean persists

2011-08-16T11:14:00.000-06:00

As of this writing, Gert is not much more than a skeleton vortex... though still clinging to tropical storm intensity. It is located approximately 550 miles south of Newfoundland and zipping off to the northeast at 26kts. There is little to no deep convection associated with it, the SST under it is 26C and will decrease rapidly along its track, and it is soon going to get absorbed by a deep mid-latitude trough. So, Gert's time as a TC is limited. And with it not becoming a hurricane, this is the first time in 160 years of records that the Atlantic has started a season with 7 named storms and 0 hurricanes.

The disturbance that exited Africa on the 6th and was crossing the Lesser Antilles yesterday is now centered near 65W in the Caribbean (this was the one that can be traced back to the Ethiopian Highlands on Aug 2). It's lacking a surface circulation, but it's persistent, and is still definitely worth keeping a close eye on. Generally, models favor this system and intensify it quite substantially in the next 5 days as it heads W-WNW toward the Yucatan area. BUT, it needs to at least become a Depression before getting concerned about anything beyond that. An aircraft will investigate the system later today.

Elsewhere, a large easterly wave exited Africa early on the 15th and is now near the Cape Verde islands. A scatterometer (a polar-orbiting satellite that can measure surface winds over the ocean) overpass earlier today reveals a fairly healthy low-level circulation... look near 12N 27W:

Please visit my tropical Atlantic headquarters.

Franklin, Gert, and possibly Harvey...

2011-08-15T10:23:00.000-06:00

During the weekend, the disturbance that was west of Bermuda (AL95) got slightly better organized and was upgraded to TD6 at 21Z on Friday. Then at 09Z on Saturday, it was upgraded again TS Franklin, the sixth named storm of the season. However, just 18 hours later, it has lost tropical characteristics and merged with a mid-latitude frontal system. A short-lived and uneventful storm, like the rest of the storms in the Atlantic basin this season so far.

To add to that theme, Tropical Storm Gert is now churning east of Bermuda... this formed from the disturbance that I mentioned on Friday that was northeast of the Lesser Antilles (AL94). The first advisory was written on this as TD7 at 03Z on the 14th. The latest intensity is 50kts and 1000mb, and heading north at 10kts. Some additional strengthening is still possible in the coming day or so before it too gets whisked away to the northern Atlantic TC graveyard. Gert is the seventh named storm of the season, and if it does not become a hurricane in a hurry, this will be the first season in 160 years of records to have 7 named storms and 0 hurricanes.

Finally, AL93, the easterly wave that was near 30W on Friday, has continued its westward trek and is now near 58W... or about 200 miles east of the Lesser Antilles. You can monitor its passage through the Lesser Antilles on radar: http://www.meteo.fr/temps/domtom/antilles/pack-public/animation/animMOSAIC2.html . It's not too organized, but has had persistent convection since exiting Africa on the 10th. This disturbance is strongly favored for intensification by the statistical models (SHIPS, LGEM, SHF5), but not so much by the dynamic models (CMC, GFS, NOGAPS, HWRF, GFDL). If it does get named, the next name on the list is Harvey.

Please visit my tropical Atlantic headquarters.

Multiple areas of interest scattered across Atlantic basin

2011-08-12T10:43:00.000-06:00

Since Emily, the Atlantic has been fairly quiet, just some easterly waves trekking across the deep tropics, but for the most part, not developing into anything.
However, two such waves (one near 45W and one near 30W) are showing signs of gradual organization. The one near 45W exited Africa on Aug 8, and the one near 30W exited Africa right on its heels on Aug 10. There is also a potential for development with a Low located near Bermuda, and one northeast of the Lesser Antilles.

The visible satellite image from 1615Z today is shown below, with the four areas of interest circled in red.

At this point, none of these disturbances are even Depressions, and none pose a threat to land in the immediate future. I will keep you posted though as any or all of these develop! The next names on deck are Franklin, Gert, Harvey, and Irene.

Please visit my tropical Atlantic headquarters.

Emily reforms just east of the southern Florida peninsula

2011-08-06T16:17:00.000-06:00

The remnants of Emily finally acquired the organization required to be classified as a Depression, and at 21Z today, TD Emily was reborn. The intensity is 25kts and 1012mb, and the heading is north at 7kts. The center is located just offshore of Fort Lauderdale FL, but has been producing very heavy rainfall over the Bahamas for the past 24+ hours. It appears that FL will escape the precipitation, perhaps with the exception of some isolated thunderstorms.

The long-range radar loop from Miami can be found here: http://radar.weather.gov/radar.php?rid=AMX&product=N0Z&overlay=11101111&loop=yes and once Emily is further north, the loop from Melbourne will be more practical: http://radar.weather.gov/radar.php?product=N0Z&rid=mlb&loop=yes

Since the system did not "sneak under the westerlies", it lifted north and will continue to move north then northeast into the open ocean and come under the unfriendly influence of a mid-latitude front by Monday. So its time as being "Emily" is limited once again.

Elsewhere, an easterly wave that exited the African coast back on July 30 is approaching the Lesser Antilles, at about 55W. In addition, a new wave has just exited Africa and is near 17W... this can be traced back to the Ethiopian Highlands on Aug 2 and has a rather potent history as it trekked across the continent.

Please visit my tropical Atlantic headquarters.

Can Emily make a comeback?

2011-08-05T16:15:00.000-06:00

The remnants of Emily's low-level circulation have cleared Hispaniola and Cuba, and the "center" is now located just north of central Cuba's coast (south of Andros Island, Bahamas). There is deep convection associated with the system, but it's displaced to the east. I added a red X to the visible satellite image below to highlight where the surface circulation is located as of this writing since it's quite far from obvious. I also added estimated locations over the past two days to give you an idea of where this ill-defined circulation has traveled.

In its current state, it's not very threatening... capable of some localized flash flooding at the worst. But it is back over very warm water, and in a low-shear environment, so it's too early to completely let your guard down yet if you're in FL. Models tend to not develop this system much anymore, since it needs to undergo genesis all over again. Since this is not a deep coherent vortex, its motion isn't simply governed by the deep-layer mean flow; it could continue to sneak westward along the north coast of Cuba and enter the Gulf of Mexico. Simple barotropic models (e.g. LBAR, BAMS, BAMM, BAMD) do actually bring the system south of FL and then recurve it back into the west coast of the FL peninsula in about 3 days. However, the intensity should still be minimal, but FL can expect to get wet this weekend. The long-range radar loop from Miami can be found here: http://radar.weather.gov/radar.php?rid=AMX&product=N0Z&overlay=11101111&loop=yes

Please visit my tropical Atlantic headquarters.

Emily dissipates

2011-08-04T16:37:00.000-06:00

The dry air and encounter with Hispaniola have overwhelmed the fragile circulation that Emily had, and the final advisory was written on the storm this afternoon. The latest position estimate is between Cuba and Haiti and the heading is NW at 14kts.

Although the storm has weakened to an open trough, this does not rule out the possibility that it could regenerate once conditions improve. Depending on the details how this happens, it could be classified as 6/Franklin or maintain 5/Emily. To pull from a a 6-year old advisory written by Stacy Stewart at NHC:

THE NWS RULES GOVERNING THE NAMING OF TROPICAL CYCLONES SPECIFY THAT...WITHIN A BASIN...WHEN A CYCLONE FORMS FROM THE REMNANT OF A PREVIOUSLY EXISTING CYCLONE...THE OLD NAME/NUMBER IS RETAINED. TROPICAL DEPRESSION TWELVE HAS A COMPLEX GENESIS THAT LIKELY INCLUDES A MID-LEVEL REMNANT OF FORMER TROPICAL DEPRESSION TEN. A REVIEW OF SATELLITE AND RAWINSONDE DATA OVER THE PAST WEEK OR SO SUGGESTS THAT A SECOND DISTURBANCE APPROACHED AND COMBINED WITH THE MID-LEVEL REMNANT OF TROPICAL DEPRESSION TEN ON 20 AUGUST. BECAUSE IT IS IMPOSSIBLE TO DETERMINE WHICH OF THESE TWO SYSTEMS IS ASSOCIATED WITH TODAY'S GENESIS...WE HAVE ELECTED TO USE THE DESIGNATION TWELVE RATHER THAN TEN FOR THE NEW DEPRESSION. THIS SITUATION DIFFERS FROM LAST YEAR'S REGENERATION OF IVAN...IN WHICH THE LOW-LEVEL REMNANT OF THAT SYSTEM REMAINED A DISTINCT FEATURE THAT COULD BE FOLLOWED CONTINUOUSLY UNTIL IT REGENERATED.

So in this case from 2005, TD10 dissipated, and after careful analysis, the new circulation that formed from its remnants did not have enough of TD10 in its gene pool to keep the same name. TD12 was classified as a new system from the remnants of TD10 (TD11 had formed elsewhere in the meantime). Incidentally, TD12 would eventually hit southern FL as Tropical Storm Katrina and then the northern Gulf coast as Hurricane Katrina.

Many models do re-develop this storm, and the track passes over the Bahamas on Friday and Saturday, then recurving out to sea before reaching Florida. The forecast intensity spread in 2 days (near closest approach to FL) is anywhere from 25-60kts for the models that re-develop it, and of course nothing for those that don't.

Please visit my tropical Atlantic headquarters.

Emily falling apart as it approaches Hispaniola

2011-08-03T13:36:00.000-06:00

Since getting named on Monday evening, Tropical Storm Emily has intensified slightly to 45kts, but has also been struggling to organize. A combination of vertical shear and environmental dry air has hindered the storm from strengthening very much, which is certainly welcome news to the Dominican Republic and Haiti (the eastern and western nations of Hispaniola, for anyone who isn't familiar with it). As of 15Z today, Emily was located about 120 miles south of Santo Domingo in the Dominican Republic and tracking W at 12kts. As you can see in the satellite image, the low-level center (at about 17N 70.5W) is quite removed from the majority of the deep convection.

As it nears and traverses the mountainous island of Hispaniola, it will likely lose what structure it has, and undergo genesis again once it exits the island in about 24 h. However, just because the storm isn't intense when measured in terms of wind speed, even tropical storms can be extremely dangerous to flood-prone areas due to large rainfall amounts... e.g. flash flooding, mudslides, etc. The graphic below shows the latest 5-day forecast precipitation swath from the HWRF model (up to 24" over areas of Hispaniola with large amounts along the US coast from FL to NC later in the period):

In the longer range, models continue to indicate that Emily will graze or miss the US east coast, recurving very close to the coastline. The current official forecast track as well as watches and warnings can be found here: http://www.nhc.noaa.gov/storm_graphics/AT05/refresh/AL0511W5_NL+gif/

Please visit my tropical Atlantic headquarters.

Tropical Storm Emily becomes 5th named storm of the season

2011-08-01T17:44:00.000-06:00

Based on extensive aircraft reconnaissance today, the disturbance near the Leeward Islands was upgraded to TS Emily. The intensity is 35kts and 1006mb, and it's located 50 miles WSW of Dominica (the island between Guadeloupe and Martinique). I have a radar loop available at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/emily11/Emily_01-02Aug11.gif

There are tropical storm warning issued for the southern Leeward Islands, Puerto Rico, and Dominican Republic. The latest watches and warnings can be found here: http://www.nhc.noaa.gov/storm_graphics/AT05/refresh/AL0511W5+gif/

The official forecast brings the storm over Hispaniola on Wednesday, the Bahamas on Thursday-Friday, and into south Florida on Saturday as a minimal hurricane. As usual though, intensity forecasts are prone to errors, so this will be watched very closely, but the interaction with Hispaniola should limit the intensity.

Please visit my tropical Atlantic headquarters.

Disturbance nearing Lesser Antilles, poised to strengthen

2011-08-01T09:09:00.000-06:00

The disturbance I mentioned in the July 29 update has gotten better organized over the weekend, though is just short of being classified as a Tropical Depression (as verified by an aircraft reconnaissance flight into it this morning). It's been 8 days since this wave left the African continent, and now it's located about 250 miles east of Martinique in the Windward Islands, and tracking WNW at 12kts. At this pace, it will cross the Leeward Islands on Tuesday morning, be near Puerto Rico on Wednesday morning, and near the Dominican Republic on Thursday morning.

At this point, the bulk of models do not indicate that this storm will enter the Gulf of Mexico, but rather recurve before reaching the US coast, or make landfall somewhere along the east coast. This far out, anyone in the Greater Antilles, Bahamas, and southeast US should be paying close attention. The plot below from Jonathan Vigh shows the most recent series of model track forecasts, including models that range from very basic to very sophisticated and everything in between.

As far as intensity goes, it does not appear that there is an urgent risk of an intense hurricane in the next several days, so areas such as the Leeward Islands, Puerto Rico, and Hispaniola should be mostly concerned with the rain/flood threat it will bring.
If and when this system reaches Tropical Storm intensity (sustained winds of 35kts), it will be named Emily.

Please visit my tropical Atlantic headquarters.

TS Don making landfall, new disturbance brewing...

2011-07-29T17:31:00.000-06:00

Tropical Storm Don has not gotten much better organized, and is now nearly ashore near Corpus Christi, TX. The storm surge north of the landfall location should be quite small, perhaps 1-2', but the rain will be very heavy (and welcome), and there's always an elevated risk of tornadoes with landfalling tropical cyclones of any intensity.
The latest radar loop from Corpus can be found at http://radar.weather.gov/radar.php?rid=CRP&product=N0R&overlay=11101111&loop=yes

The intensity as of 21Z today was 45kts and 1004mb, and heading WNW at 14kts. Being such a small system, it will dissipate quickly once inland.

Much further east, there's an impressive easterly wave near 10N 45W (1100 miles east of the Lesser Antilles) that exited the African coast back on July 24. It is very well organized, and nearly every model is forecasting this to become a hurricane within 4-5 days as it heads WNW toward the Leeward Islands. If named, the next name on the list is Emily. More on this as it develops...

Please visit my tropical Atlantic headquarters.

Easterly wave finally in Gulf of Mexico... possible TX landfall

2011-07-27T09:35:00.000-06:00

The African easterly wave that exited the African coast on July 17 (and the same one I mentioned in my last update on July 22) has become better organized and has entered the Gulf of Mexico between the Yucatan Peninsula and Cuba. The deep convection is displaced slightly to the southeast of the low-level center due to some vertical shear. The SST is 28.8C and the vertical shear is expected to remain favorable.

The majority of reliable models bring this system up to a strong tropical storm or even minimal hurricane in 2-3 days prior to a landfall in southern-central Texas on Friday night. Though not yet a Depression, it could quickly intensity to TS Don in the coming 24 hours. There will be an aircraft reconnaissance flight into the disturbance later today for an accurate intensity measurement.

Please visit my tropical Atlantic headquarters.

Bret and Cindy come and go, possible action nearing Lesser Antilles

2011-07-22T08:46:00.000-06:00

Sorry for the lack of updates during the past two named storms... I was vacationing in Miami since the 14th and got to experience the distant effects of Bret first-hand (wave height was 12" instead of 2" on July 17-18).

Tropical Depression 2 formed off the eastern coast of southern Florida on July 17, quickly became TS Bret, and zipped off to the northeast. It reached a peak intensity of 55kts (996mb central pressure), and has since weakened, now barely holding onto Tropical Depression status. As of the final advisory at 15Z today, the intensity was 30kts, 1009mb, and tracking NE at 18kts. It's located about 550 miles east of Delaware and has lost its tropical characteristics.

On July 20, Tropical Storm Cindy formed about 500 miles east of Bermuda. It has always had a subtropical appearance, and it continues to struggle maintaining TS status. The SST under the storm is 19C and dropping fast (will be about 13C in 24 hours) and the vertical shear is 25kts.

Elsewhere, there is an easterly wave located at about 55W. This wave exited the African coast on July 17, and has had persistent convection associated with it. The limited number of statistical forecast models that have been run on it generally develop this system and bring it WNW toward Hispaniola and Cuba over the next 3-5 days. We will see what the dynamical models produce once they are run on it later today. Should this get named, the next name on the list is Don.

Please visit my tropical Atlantic headquarters.

Arlene makes landfall

2011-06-30T09:05:00.000-06:00

At about 15Z today, the center of Tropical Storm Arlene crossed the Mexican coastline near Cabo Rojo (about 45 miles south of Tampico) with 55kt sustained winds and up to a foot of rain further inland over the higher terrain.

Over the next day, it will weaken, produce a lot of rain, and eventually completely dissipate. Elsewhere, the basin is quiet... but when the time comes, the next name on the list is Bret.

Please visit my tropical Atlantic headquarters.

First storm of the season forms in Bay of Campeche

2011-06-29T10:05:00.000-06:00

Not long after yesterday's update was sent out, the area of disturbed weather was upgraded to Tropical Storm Arlene, the first of the season. As of the 15Z advisory today, it is a 45kt storm with a 1000mb central pressure. It's located 155 miles ESE of Tampico MX and heading W at 7kts. As expected, the vertical shear has decreased, and the storm was quick to take advantage of the improved environment. Further strengthening is forecast prior to landfall, perhaps nearing or reaching hurricane intensity.

The track should bring the storm onto land during the overnight hours very close to Tampico. Even at minimal hurricane intensity, by far, the greatest threat is the heavy rain that comes with tropical systems. Strong winds and a 2-4' storm surge will also occur along the coast, especially north of where the center crosses the coast. You can monitor the latest track forecast, watches, and warnings at http://www.nhc.noaa.gov/storm_graphics/AT01/refresh/AL0111W_NL+gif/

Finally, you can follow Arlene on radar at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/arlene11/Arlene_29-30Jun11.gif

Please visit my tropical Atlantic headquarters.

Bay of Campeche disturbance getting organized

2011-06-28T13:47:00.000-06:00

Over the past week or so, there has been a persistent area of convection and depressed surface pressures over the Yucatan Peninsula and into the Bay of Campeche. This disturbance is currently centered near 21.0N 93.4W, tracking WNW at 6kts, and has a 1006mb central pressure. The circulation is broad and ill-defined, but has been improving gradually.

This system is expected to continue organizing as the sea surface temperatures remain at about 28.5C and the vertical shear decreases from the current 15kts to around 7kts by tomorrow evening. Landfall will occur sometime Wednesday night into early Thursday morning near Tampico MX, and by far, the most significant threat will be the heavy rainfall. The graphic below shows the forecast precipitation totals starting today and running through Sunday:

Should this get named, the first name this season is Arlene. Climatologically, the first named storm in the Atlantic forms on July 9, so this would be just slightly ahead of an average season.

Please visit my tropical Atlantic headquarters.

First day of hurricane season comes with a couple of disturbances

2011-06-01T14:01:00.000-06:00

Today is the first day of the Atlantic hurricane season. To help usher it in, there are two areas of disturbed weather to keep an eye on.

The first, a very compact system labeled AL93, has been tracking toward the southwest over the past day and has just made "landfall" near Daytona Beach FL as a 1013mb Low. It is bringing heavy rain, hail, and/or gusty winds to much of the central FL peninsula, and will soon enter the northeast Gulf of Mexico. Though unlikely, there is a chance that this will re-develop over the Gulf and head generally westward as a Tropical Storm. I won't say any more about that unless it actually survives the Florida transit.

The second area of disturbed weather is in the central Caribbean, north of Colombia/Panama centered near 12N 77W. It is nearly stationary, and although environmental conditions are unfavorable now, they could improve in 2-3 days, allowing this to develop and crawl NW-N toward the Yucatan-Cuba area.

The first couple of names on this year's roster are Arlene and Bret. Since the blog format is new this season, I'm sending the posts to the old mailing list as well.

I'd also like to point out that the CSU's June 1 Seasonal Forecast is available at http://hurricane.atmos.colostate.edu/Forecasts/2011/june2011/jun2011.pdf ... the short version is that 2011 should be an active season, though not as active as the historic 2010 season. The forecast calls for 16 named storms, 9 hurricanes, and 5 major hurricanes, or about 75% higher than average.

Please visit my tropical Atlantic headquarters.

Archives of tropical updates

2011-02-02T10:26:00.000-07:00

I know some people have been on this list (in whatever form it was) since the very early days... started in 1996. This is a long-shot, but if anyone has saved any messages from the 1996-2001 era, could you please let me know... I'd love to include them on here!
Please visit my tropical Atlantic headquarters.

Tomas re-intensifies as it passes between Haiti and Cuba...

2010-11-05T10:02:00.002-06:00

Since my last update on Monday, Tomas behaved pretty much as expected, and continues to do so. Copying directly from that update: "By later in the week, Tomas is forecast to regain hurricane status and very slowly make its way northward toward Haiti". Well, Tomas has become a hurricane again, and is currently near the tip of Haiti's southern peninsula. At 15Z, the intensity was 75kts/987mb and tracking NNE at 10kts. By far, the biggest concern with this storm is the very heavy rainfall over Haiti, eastern Cuba, and the Dominican Republic. There are many locations with Hurricane Warnings, please check http://www.nhc.noaa.gov/storm_graphics/AT21/refresh/AL2110W5+gif/ for the latest.

By early next week, Tomas will become entangled with a mid-latitude trough and become extratropical. But impressively, it's already been around as a numbered system for nearly 7 days, and probably will be around for another 3-4. My colleague Phil Klotzbach pointed out that "it would be the second most NSD [Named Storm Days] generated by a storm forming on or after October 29 since aircraft recon began in 1944. The most NSD generated by a single storm forming after October 29 is Hurricane Lili back in 1984, which generated an impressive 11.75 NSD". So, yet another anomaly for this incredibly active season that will go into the record books with the company of 1933, 1995, and 2005.

Please visit my tropical Atlantic headquarters.

Tomas weakens in the central Caribbean...

2010-11-01T11:11:00.002-06:00

For a brief period early Sunday morning, Tomas reached an intensity of 85kts (Cat 2), but has since weakened significantly in the face of hefty vertical shear. In fact, the low-level circulation is completely exposed and the convection is displaced well to the east. As I write this, there is a resurgence of deep convection over the center, but it's still getting pushed off to the east. At 15Z today, the intensity is 40kts/1005mb (a weak tropical storm) and is forecast to remain weak for another day or so until the shear relaxes and the storm can regain its organization. By later in the week, Tomas is forecast to regain hurricane status and very slowly make its way northward toward Haiti.

Reaching the 19th named storm is extremely rare, but having a named storm in November is not so rare. In recent years, November storms include Ida '09, Paloma '08, Noel '07, Gamma '05, Delta '05, Otto '04, Nicholas '03, etc, etc, etc. The end of the official hurricane season is the end of November, but nature doesn't always obey that arbitrary limit... recent post-November storms include Olga '07, Epsilon '05, Zeta '05, Odette '03, and Peter '03.

Please visit my tropical Atlantic headquarters.

Hurricanes Shary and Tomas bring a surge of activity to the end of October...

2010-10-30T08:58:00.000-06:00

Shortly after recurving away from Bermuda, Shary intensified to a 65kt minimal hurricane and is still headed out to the hurricane graveyard that is the north-central Atlantic. This makes it the 11th hurricane of the season. It's 580 miles ENE of Bermuda and racing away from the island at 35kts. It is rapidly on its way to becoming an extratropical cyclone and will get absorbed into the mid-latitude westerlies.

As I suggested in my update yesterday, the disturbance near the Windward Islands was indeed upgraded to TS Tomas once the aircraft got there to investigate it. Then, today at 15Z, it was upgraded to Hurricane Tomas, the 12th of the season. The latest intensity is 65kts/993mb and on a very definite strengthening trend. It's crossing the Windward Islands as I type this, and will head into the Caribbean, quite likely bound to become the season's 6th major hurricane in the coming days. There is a long radar loop of the hurricane at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/tomas10/Tomas_29-30Oct10.gif. Tomas is heading WNW at 13kts and this motion is expected to continue, bringing it near Jamaica in 5 days, probably as a major hurricane. All interests in the Caribbean should be watching this very closely. The latest watches, warnings, and track forecast can be found at http://www.nhc.noaa.gov/storm_graphics/AT21/refresh/AL2110W5+gif/

Please visit my tropical Atlantic headquarters.

Shary forms far east of US coast, two other disturbances worth watching...

2010-10-29T09:34:00.000-06:00

In a late-season surge of activity, there are three significant areas of tropical activity. The first of which was recently upgraded to TS Shary (03Z today), and is located about 950 miles due east of Jacksonville FL. This is the 18th named storm of the season. Intensity is estimated at 35kts/1004mb, and it is just about to begin recurvature to the NE... heading directly for Bermuda later tonight. Intensification will be limited due to the hefty vertical shear and cooling SSTs, so it's unlikely that Shary will become a hurricane. You can monitor Shary near Bermuda at http://www.weather.bm/radarLarge.asp

Elsewhere, an extremely well-organized easterly wave is nearing the Windward Islands. It existed the African coast on Oct 23 and has been quite impressive since then, particularly in the past couple of days. There is a 1006mb Low analyzed with the system, and a plane will be flying into it later today to gather more accurate intensity data. It's quite likely that this will be upgraded to TD 19 then TS Tomas within 24 hours. It's presently about 400 miles east of Trinidad and heading WNW toward the southern Windward Islands. Over the next several days, the eastern Caribbean environment will be favorable for significant development, so this could become the season's 11th hurricane. The Windward Islands, Virgin Islands, Puerto Rico, and Hispaniola should be very alert for possible impacts.

Finally, there's another area for potential development in the central Atlantic, about 1200 miles east of TS Shary. It also has its origins from an easterly wave that exited Africa back on Oct 19 (it's the one I mentioned in my update on Oct 21 when it was near the Cape Verde islands). Conditions are fairly hostile for this system to develop, but if it should, it would be TD22 then TS Virginie, assuming the previous system goes first.

Also assuming that Tomas forms from the disturbance nearing the Windward Islands, that would bring the season up to 19 named storms, a tie with the infamous 1995 season. 2010 is most certainly in the top 4 seasons in recorded history for activity, even if nothing else forms. As of today (not counting current or future developments), it has seen five major hurricanes, four of which were Cat 4, ten hurricanes, among the most ever recorded in a season, and 18 named storms, also among the the most ever recorded in a season!

Please visit my tropical Atlantic headquarters.

Richard becomes season's 10th hurricane, hits Belize...

2010-10-25T10:30:00.000-06:00

Over the weekend, Richard intensified to an 80kt Cat 1 hurricane prior to making landfall on Belize and tracking across the Yucatan peninsula. This was the 4th storm to hit that small section of coast (Alex, Karl, Matthew, Richard) this season. The radar loop of the storm's approach and landfall is at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/richard10/Richard_24-25Oct10_belize.gif

At 15Z today, Richard was downgraded to a 30kt Depression and is still over the southern Yucatan peninsula. There will most likely be very little left of the vortex once it enters the Bay of Capeche, and all model guidance suggests a minimal TS or remnant low as it limps W-NW across the Bay.

With yet another hurricane added to the ranks, the rarity of such an active season not having a US landfall is even more striking. In the last 110 years, there has never been a season with 10 hurricanes and 0 US hurricane landfalls. You may recall that Ike was the last time the US was hit by a hurricane, and that was in early Sept 2008.

Please visit my tropical Atlantic headquarters.

Richard nearly stationary east of Nicaragua...

2010-10-22T11:14:00.000-06:00

Since yesterday's update, very little has changed. Richard is still a 35kt tropical storm, still forecast to head toward Belize and the Yucatan peninsula, and still forecast to become a hurricane prior to that first landfall. It's presently in a very weak steering environment, so it's drifting, most recently to the west at 3kts. Over the next two to three days, the forward motion should pick up as a ridge moves in to the north of it, sending it westward into Belize by Monday morning. I will have a full radar loop from Belize once the storm is within radar range, so stay tuned.

Depending on how intense it gets prior to that landfall, and how quickly it traverses the Yucatan peninsula, it will enter the southern Gulf of Mexico either as a remnant swirl or as a re-intensifying tropical storm. Given the magnitudes of those unknowns, any forecast beyond that is total speculation. To be on the safe side though, areas on the north and east US Gulf coast should be keeping a close eye on Richard next week.

The easterly wave that was near the Cape Verdes continues to look impressive on satellite imagery, but is not yet a Depression. It's still near the Cape Verdes, but moving toward the NW. It only has another 1-2 days to develop before it moves into much stronger vertical shear.

Please visit my tropical Atlantic headquarters.

Richard forms in western Caribbean...

2010-10-21T09:23:00.000-06:00

The area of disturbed weather that I mentioned in my last update 6 days ago has been festering and very slowly getting better organized. As several global models predicted about a week ago, a tropical storm has emerged from the southwestern Caribbean! At 03Z today, it was upgraded to TD19, then at 15Z today, upgraded again to TS Richard based on aircraft recon, making it the 17th named storm of the season. It's located about 200 miles ENE of the Nicaragua/Honduras border and the intensity is 35kts/1006mb. Since 1900, only three other seasons have had this many named storms: 1933, 1995, and 2005, so this is among the most active seasons in recorded history. Also, the name Richard has never been used before in the Atlantic, though it has been in the rotation for 30 years.

Richard is expected to continue strengthening as it heads slowly toward Belize and the Yucatan peninsula... the 5th storm this season to affect that area (Alex, Karl, Matthew, and Paula have already made their unwelcomed visits). The official forecast brings Richard to a Yucatan landfall (as a Category 1 hurricane) early on Monday morning, then enters the southern Gulf of Mexico by Tuesday morning. Beyond that, the states along the north and east Gulf coast (particularly Florida) should be watching this system closely.

Elsewhere, a surprisingly well-organized easterly wave has exited the African coast and is presently south of the Cape Verde islands and showing signs of a surface circulation. The shear and SSTs are currently not inhibitive for this to become a tropical cyclone in the next couple of days, but the environment does become more hostile after that.

Please visit my tropical Atlantic headquarters.

Paula dissipates over Cuba...

2010-10-15T08:59:00.000-06:00

Over the last couple of days, Paula skirted turned toward the NE, encountered significant shear, skirted along the northwest coast of Cuba, and just recently has the final advisory written on it as a dissipated Depression over central Cuba. Yet another landfall to add to the seasonal count, and yet another one that the US dodged.

With the assistance of my colleague Phil Klotzbach, I have a 159-year climatological probability of hurricane landfalls anywhere along the US coast. In seasons that are this active (as measured by the Net Tropical Cyclone activity, or NTC, which is currently 173.5 compared to an average season with NTC of 100), the US has a 95.4% chance of being hit by at least one hurricane of any category. Moving the threshold up to major hurricanes only (Cat 3+), the US has a 20.5% chance of being hit by at least one major hurricane. Clearly, the US coast has been quite fortunate so far this season.

Back to the current state of the tropics, there are hints of a tropical disturbance festering in the extreme southwestern Caribbean, over Panama. There is low-level convergence along the monsoon trough, some enhanced vorticity centered near Panama, and persistent convection also centered over Panama. In mid-October, those ingredients at that location is climatologically favored for a north-moving western Caribbean hurricane. In several long-range global models, a strengthening storm does emerge from this cocoon in the coming 3-4 days, then make its way generally northward toward Cuba in about 9 days.

Please visit my tropical Atlantic headquarters.

Category 2 Hurricane Paula stalling in Yucatan Straights...

2010-10-13T10:31:00.000-06:00

Aircraft recon into Paula on Tuesday afternoon found much stronger winds than expected, and it was immediately upgraded to an 85kt CAT2 hurricane with a central pressure of 981mb. Since then, it has has changed very little... at 15Z today the intensity is 85kts/984mb. Though the forecast is for gradual weakening in the face of increasing vertical shear, a short-term temporary increase is possible based on satellite imagery. There is another recon plane en route to the storm as I type this, so in a couple of hours we will know better what the exact intensity is. It's a rather small storm, so changes (either increases or decreases) can happen dramatically.

Looking at the long radar loop available at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/paula10/Paula_12-13Oct10.gif, you can see that the motion has slowed down quite a bit, and is now drifting to the NE at roughly 3kts. The forecast track is for continued slow motion, and turning to the E, then dissipating over the mountains of Cuba. However, there is large model guidance spread, and anything from completely stalling in the Yucatan Straights for a few days to getting picked up by the trough and heading NE over Cuba/Florida/Bahamas is within the realm of possibilities. If you are in any of those areas, you can keep up to date on the latest watches and warnings at http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/144014.shtml?5day#contents

Please visit my tropical Atlantic headquarters.

Hurricane Paula heading for the Yucatan...

2010-10-12T10:27:00.000-06:00

A lot has happened in 24 hours... the disturbance that was off the Nicaragua/Honduras border rather quickly got better organized. A plane flew into the system and found much stronger winds than expected, and at 21Z yesterday, it was upgraded to TS Paula with 50kt winds and a 1000mb central pressure. Just 12 hours later, it was upgraded to Hurricane Paula, the 9th of the season. The intensity as of 15Z today is 65kts and 991mb, and it's located 150 miles SSE of Cozumel, Mexico and heading NNW at 9kts. Hurricane warnings are in effect for the eastern coast of the Yucatan Peninsula: http://www.nhc.noaa.gov/storm_graphics/AT18/refresh/AL1810W_NL+gif/

It is forecast to continue intensifying, and also to slow down. In 5 days, it is forecast to be in the Yucatan Straights, not far from where it is now. However, increasing shear is expected to hit it in about 3 days, so it might not make it to a major hurricane.

You can monitor its structure and movement via a radar loop from Cancun: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/paula10/Paula_12-13Oct10.gif

Please visit my tropical Atlantic headquarters.

Otto becomes extratropical, disturbance brewing in western Caribbean...

2010-10-11T08:50:00.000-06:00

Otto spent 1.5 days as a hurricane, though was visibly losing its tropical characteristics in a hurry (weaker and displaced convection, frontal bands, etc.). At 03Z on Sunday, it was downgraded to a TS, then twelve hours later, advisories were ceased on the system as it became an extratropical cyclone about 400 miles west of the Azores.

There is a 1008mb Low associated with a disturbance that has been festering in the western Caribbean for several days (I mentioned it in my update on Friday). It's currently located on the tip of the Nicaragua/Honduras border and drifting to the WNW. The majority of models gradually develop this system into a TS (Paula) as it heads NW toward Cozumel, then recurving to the NE toward Cuba/Florida. Intensification should be somewhat limited due to the expected proximity to land throughout the next few days.

Please visit my tropical Atlantic headquarters.

Hurricane Otto heading out to the north central Atlantic...

2010-10-08T08:50:00.000-06:00

Since my last update on Tuesday, the disturbance I referenced was upgraded to STD17 on Wednesday morning, STS Otto on Wednesday afternoon, TS Otto on Thursday morning, and now Hurricane Otto as of 15Z today. Sorry about the lack of updates since Tuesday!
The storm took a while to get organized and acquire purely tropical characteristics, and as such, it was sub-tropical for at least a couple of days. As I write this, it definitely is tropical, and has a rather impressive satellite presentation with nearly -85C cloud tops in the CDO. There is not yet an eye apparent in the VIS or IR, but that could certainly change in the coming hours.
The current intensity is 65kts and 979mb, making Otto the 8th hurricane of the season. Right now, we're just one TS away from matching the active 2008 season which had 16 named storms, 8 hurricanes, and 5 major hurricanes. The storm is located about 550 miles north of Puerto Rico and tracking ENE at 15kts. The forecast is for some additional strengthening, then a rapid transition to extratropical as it merges with a mid-latitude trough which will whisk the system out to the north central Atlantic over the next 3 days.

Elsewhere, there's a low-level swirl associated with an easterly wave located north of Panama. This doesn't look too likely to develop in the foreseeable future.

Please visit my tropical Atlantic headquarters.

Disturbance near Windward Islands getting organized...

2010-10-05T09:34:00.000-06:00

Back on Sept 25, an easterly wave exited the African coast and has been making its way westward through the deep tropics. For much of the last 1.5 weeks, it has been a feature of interest, but not great interest. In the past couple of days however, the circulation and convection have become more concentrated, and the system is now just north of Puerto Rico. Using the long-range radar from San Juan, we can see the weak circulation: http://radar.weather.gov/radar.php?rid=JUA&product=N0Z&overlay=11101111&loop=yes.

It's in about 10kts of vertical shear (expected to decrease slightly over the next couple of days) and over 29C water (remaining steady over the next couple of days). The majority of models now develop this system, bringing it to TS intensity within a day, and hurricane intensity in 2-4 days. As far as the track goes, models are in agreement that it will recurve out to the open ocean in about 2 days... drifting to the NW prior to that.
The next name on the list is Otto.

It's truly remarkable that the US has not had a hurricane landfall this season... it's been quite an active season so far, with 14 named storms, 7 hurricanes, and 5 major hurricanes. But, countries to our south haven't been so fortunate. It's been a very bad year for landfalls and tropical cyclone effects in most of central America and Mexico... also Bermuda and Newfoundland had noteworthy, historic encounters.

Please visit my tropical Atlantic headquarters.

Nicole dissipates, easterly wave getting organized...

2010-09-30T09:50:00.000-06:00

Since my update on Tuesday, TD16 was briefly upgraded to TS Nicole, then Nicole rapidly lost its tropical characteristics and merged with a mid-latitude trough... before even reaching Florida! This was a very unusual situation, and is resulting in a very unusual heavy rain event up the entire US east coast. Everywhere from FL to ME and from the coast to hundreds of miles inland, flooding rains are the big story.
See http://www.weather.gov/largemap.php for a real-time summary of the watches and warnings associated with this event, and http://www.hpc.ncep.noaa.gov/discussions/nfdscc5.html for a history of what has fallen so far in select locations.

Elsewhere, there's a broad circulation associated with an (possibly 2 really close) easterly wave located about 800 miles east of the Windward Islands. Though not widely favored by global models for development, it looks fairly impressive on satellite imagery.

Please visit my tropical Atlantic headquarters.

Lisa and Matthew are out of the picture, TD16 forms...

2010-09-29T10:04:00.000-06:00

During the last three days since my last update, Lisa and Matthew fizzled out (Lisa drifted north over cold water in the far eastern Atlantic and Matthew dumped ridiculous amounts of rain over much of central America and dissipated inland), and a new large area of disturbed weather has been brewing over the western Caribbean... perhaps the one that many of the global models hinted at over a week ago.

That disturbance was upgraded to TD16 today at 15Z based on satellite and surface observations... and a recon aircraft just took off for a flight into the system as I type this. The intensity estimate is 30kts and 1001mb; it's located about 180 miles S of Havana and tracking NNE at 9kts. It is forecast to slowly intensify and head NNE, bringing it over Cuba then into south Florida most likely as a TS. There are Tropical Storm Warnings for central Cuba, the Bahamas, and the Florida peninsula from Key West to West Palm Beach. The next name on the list is Nicole.

For a little bit of hurricane history, on this day 12 years ago, large and tenacious Hurricane George made landfall near Biloxi, MS as a CAT2 storm: http://upload.wikimedia.org/wikipedia/commons/d/d0/Hurricane_Georges_28_sept_1998_2043Z.jpg

Please visit my tropical Atlantic headquarters.

Lisa downgraded to TD, disturbance in southern Caribbean getting better organized...

2010-09-23T10:04:00.000-06:00

Lisa has been plagued by a hostile environment with moderately strong vertical shear and moderately dry low-mid level air... a bad combination if you're a tropical cyclone. As a result the storm was downgraded to a Depression at 09Z today, and remains so at 15Z. However, there is a 1-2 day window of opportunity beginning now where the environment should improve before drier air invades again. Regardless, Lisa will remain a weak storm and far from any land.

On the other hand, that area of disturbed weather that was skimming the Venezuelan coast the past couple of days is now located north of western Columbia and heading west toward Nicaragua. The environment in which this system is embedded couldn't be any more conducive for significant development: 30C SSTs, 5 kts of vertical shear, and huge values of ocean heat content. Though it has taken nearly a week to get spun up (not out of the norm), it appears that it is now nearly a Depression and could quickly intensify to TS Matthew. As I mentioned before, a system like this must be watched very closely, because it WILL affect land, and probably have 1-3 landfalls in its lifetime. I've been perusing the global model output regularly, and an overall trend and consensus is to bring the storm gradually WNW through much of the western Caribbean, then perhaps a NW turn to bring it up into the Yucatan Straights area by the middle of next week.
A recon plane left St. Croix early today and is conducting multiple penetrations through the system as I type this. So far, a central pressure of 1008mb has been found, along with 36kt flight-level winds (corresponds to nearly tropical storm force at the surface).

Please visit my tropical Atlantic headquarters.

Igor racing by Newfoundland, Lisa forms in eastern Atlantic, disturbance crossing Windward Islands...

2010-09-21T09:59:00.000-06:00

Igor is still officially a hurricane, though is in the midst of its extra-tropical transition. Storms like this that are over very cold SSTs (15F) and in 50kts of vertical shear can still be very powerful thanks to baroclinic enhancement. The same trough that's steering and shearing it is providing an energy transfer to the dying [formerly-barotropic] hurricane. Here's one model's (HWRF) representation of an along-shear vertical cross-section of the storm showing a barely barotropic structure: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/hwrf/2010/plots/AL11/2010AL11_HWRFXSEC_201009210600_F000.PNG

At 15Z, Igor's intensity was 65kts, 952mb, and cruising by Newfoundland at 40kts. It probably has another 6-12 hours remaining as a system that NHC tracks. It has been a hurricane for nearly 10 days and using NTC as a measure of seasonal activity, has provided ~40% of a typical season's entire activity by itself (NTC is Net Tropical Cyclone activity which combines the numbers and longevities of the various storm intensities --TS, H, MH-- and compares them to climatology)!

At 03Z today, the easterly wave in the far eastern Atlantic was upgraded to TD14, then six hours later, to TS Lisa, the 12th named storm of the season. It's located about 530 miles WNW of the Cape Verde islands, and drifting to the north. It is forecast to continue drifting to the north, and only intensify slightly, probably never reaching hurricane status and never affecting any land.

Back on the 16th, I mentioned a "suspicious surge of southwesterlies" about 1700 miles east of the Lesser Antilles. Well, it has indeed festered for a few days, and is now a fairly impressive disturbance located just north of the central Venezuelan coast. Conditions are favorable for further (and significant) development, so this will be watched very closely. The next name on the list is Matthew.

Please visit my tropical Atlantic headquarters.

Igor passes close to Bermuda, new disturbance in eastern Atlantic...

2010-09-20T12:40:00.000-06:00

Hurricane Igor made its closest to Bermuda right around midnight local time as forecast. A peak wind of 81kts was reported on the island, and the minimum pressure at that time was 955mb. The radar loop showing the approach is here: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/igor10/Igor_19-20Sep10.gif (the radar and/or network was down on Bermuda as the eyewall neared, so the loop cuts off just prior to closest approach).
At 15Z today, the intensity was 65kts (minimal hurricane) and 960mb. Tropical storm force winds extend 300 miles to the NE and NW of the center, and 12' seas extend out to 800 miles from the center in the southwest quadrant. A tropical storm warning is now in effect for eastern Newfoundland, but by Tuesday morning, the long-lived (12 days) powerful hurricane will begin its extra-tropical transition as it merges with a mid-latitude trough.

The final advisories were written on Karl and Julia on Saturday 09Z and Monday 15Z, respectively.

The easterly wave that I mentioned on Friday has continued to get better organized and now has a 1007mb Low associated with it. It's located about 450 miles west of the Cape Verde islands and drifting to the NW. There's also an easterly wave right on the African coast. Both of these will be watched closely, and the next names are Lisa and Matthew.

Please visit my tropical Atlantic headquarters.

Igor, Julia, and Karl still all hurricanes, Karl becomes 5th major hurricane...

2010-09-17T10:08:00.000-06:00

Igor is still holding onto major hurricane status (it's been 5 days now) with winds of 105kts and a 945mb central pressure. It's an extremely large storm, with tropical storm force winds extending 250 miles from the center on the front-left quadrant, and hurricane-force winds extending 90 miles out in the same quadrant. It continues to slowly make it way toward Bermuda, and a closest approach is still forecast to take place Sunday night into Monday morning... Bermuda now has a hurricane watch in effect. You can monitor weather conditions at Bermuda here: http://www.ndbc.noaa.gov/show_plot.php?station=bepb6&meas=wdpr&uom=E&time_diff=-4&time_label=EDT and there's a radar loop available here: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/igor10/Igor_19-20Sep10.gif

Julia has been slow to weaken, but is now estimated to be 75kts and 981mb. It's been moving quite a bit further west than expected, and the relatively tiny storm is only about 800 miles due east of Igor and it's huge circulation. The forecast is for continued weakening and a turn to the NW then recurving by 55W.

2010 is shaping up to be quite a historic season... during the overnight hours, Karl rapidly intensified to 105kts, making it the fifth major hurricane of the season, and the furthest south a major hurricane has ever existed in the Gulf of Mexico. It also made a turn to the WSW, steering it directly into the city of Vera Cruz (Mexico's oldest and largest port with a population of ~ 700,000 and 490 years of history). The city has never experienced a major hurricane, so this will probably be quite destructive and worthy of retiring the name Karl (which has been in rotation since the beginning of naming hurricanes)! Only 3 other "K" storms have been retired: Klaus '90, Keith '00, and Katrina '05. As I type this message, Karl is making landfall with an intensity of 105kts and a central pressure of 967mb. Not only will the powerful winds be destructive, but flooding rains (up to 15" forecast) and a significant 12-15' storm surge. There is a radar loop of Karl here: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/karl10/Karl_16-17Sep10.gif showing an eyewall replacement cycle, subsequent eyewall contraction, and landfall.

An educational tidbit can be gathered from Igor and Karl: they are both 105kt storms (as verified by aircraft) yet Igor is about 4 times larger than Karl. With tropical cyclones, it's important to realize that size and intensity are not related. Another contrast is Katrina '05 and Andrew '92... at landfall, Andrew was quite a bit stronger than Katrina (Cat5 vs Cat3), but was a fraction of the size. I cannot resist the opportunity to use a memorable quote from Yoda in Star Wars (Empire Strikes Back): "Size matters not. Look at me. Judge me by my size, do you? And well you should not, for my ally is the Force, and a powerful ally it is."

The area I described yesterday with a surge of southwesterlies continues to look interesting, and more global models are beginning to pick up on possible tropical cyclone formation from it. This area is at about 10-15N and 35-40W.

There's also a potent easterly wave that recently exited the African coast and is now located near the Cape Verde islands. This will be watched closely in the coming days for development as well. The next names on the list are Lisa and Matthew.

Please visit my tropical Atlantic headquarters.

Three simultaneous hurricanes

2010-09-16T10:31:00.001-06:00

From Phil Klotzbach:

With Karl becoming a hurricane, we have three hurricanes at the same time. This is a pretty rare occurrence. The only other years that this has occurred are 1893, 1926, 1950, 1961, 1967, 1980, 1995, and 1998. 1998 even had four hurricanes at the same time! For those that are interested, the time periods with three hurricanes are as follows:

August 17, 1893 00Z    – August 24, 1893 12Z 

September 12, 1926 12Z – September 14, 1926 00Z 

August 31, 1950 00Z    – August 31, 1950 06Z 

September 2, 1950 12Z  – September 4, 1950 18Z 

September 7, 1961 00Z  – September 12, 1961 06Z 

September 10, 1967 06Z – September 11, 1967 00Z 

September 12, 1967 00Z – September 12, 1967 06Z 

September 14, 1967 12Z – September 16, 1967 06Z 

September 8, 1980 06Z  – September 8, 1980 18Z 

August 30, 1995 18Z    – August 31, 1995 12Z 

September 23, 1998 18Z – September 27, 1998 18Z

Please visit my tropical Atlantic headquarters.

Igor heading for Bermuda, Julia weakening, Karl heading for Mexico a second time... And another worthy headline: three simultaneous hurricanes in the Atlantic!

2010-09-16T10:23:00.000-06:00

Igor has not dropped below the CAT4 threshold, and is presently a 120kt storm with a central pressure of 934mb. It is located 910 miles SSE of Bermuda and heading NW at 6kts. It is forecast to maintain major hurricane status through Monday when it begins recurving and interacting with a mid-latitude trough.
The attached file shows the latest suite of model forecasts of Igor's track. There is very little spread among the models, indicating a greater deal of certainty in the forecast. Though not shown on that map, the closest approach occurs 90-96h from the 06Z initialization, which is late Sunday night into early Monday morning. I will make a running radar loop (real-time, accumulating frames) and provide a link to it as the time gets closer.

Julia has entered a more hostile environment as expected, and has weakened... the satellite presentation is much worse today than it was yesterday. As such, the intensity is down to 85kts and 971mb. It is in the open eastern Atlantic, far from anything, and will continue to weaken in the face of increasing vertical shear.

Karl made landfall on the Mexico/Belize border as a 55kt tropical storm, and was barely phased by the flat terrain of the Yucatan peninsula. It exited the peninsula in the early morning hours on Thursday and was very quick to regain its organization. At 15Z today, it was upgraded to a hurricane, the sixth of the season, and is forecast to continue intensifying, perhaps nearly to a major hurricane, before it makes its second and final landfall near Poza Rica on Friday evening. Hurricane Watches and Warnings are in effect, and you can see the latest here: http://www.nhc.noaa.gov/storm_graphics/AT13/refresh/AL1310W5_NL+gif/. The current intensity is 65kts and 983mb and increasing fairly rapidly.

Elsewhere, there is a suspicious surge of southwesterly winds in the area of 5-10N, 30-40W (about 1700 miles east of the Lesser Antilles) and some scattered deep convection associated with the resulting convergence. If that festers for a few more days, a low-latitude tropical disturbance could be in the cards. Something worth keeping an eye on in the coming days, since low-latitude systems are much less likely to recurve before reaching the US.

I'll dedicate today's update to my grandfather, James McNoldy, who passed away this past February, but would be 94 today. He once told a story of his WWII assignment (maintaining and repairing aircraft in Iceland) and the intense storms they'd get there. Once in a while, the remnants of a tropical cyclone make their way up to Greenland, the UK, Portugal, and Iceland, and if you're on an airfield fixing aircraft, you'd notice things like that!

Please visit my tropical Atlantic headquarters.

Igor and Julia both CAT4 hurricanes, Karl forms and hits Yucatan...

2010-09-15T09:59:00.000-06:00

Igor is still heading WNW and is still a Category 4 hurricane (has been since Sunday afternoon!). The 15Z intensity is 115kts and 942mb, but there was a nighttime intensification period during which it reached 135kts and 925mb... the strongest of its lifetime. It's located about 1055 miles SE of Bermuda and heading WNW at 7kts. In the coming days, Igor's intensity will likely fluctuate but remain very strong, and the track will bend a bit more to the NW. This will bring the hurricane very close to Bermuda by Sunday morning.

Tuesday evening, Julia experienced a period of rapid intensification where the pressure fell 24mb in 6 hours and the wind speed increased 25kts in the same time. As of 15Z, the intensity is 115kts and 950mb. This makes it the forth Category 4 hurricane of the season, and the easternmost CAT4 hurricane on record. Never in recorded history has there been four CAT4 storms so early in the season (we've had Danielle, Earl, Igor, and Julia all by Sept 15). It is also only the second time that two CAT4 storms have existed at the same time (the other time was in 1926). So Julia has certainly become a storm for the record books, as has the 2010 season!

The disturbance that has been tracking through the Caribbean was upgraded to TS Karl at 21Z yesterday based on an aircraft recon flight into the system. Since being named, it quickly intensified to a 55kt storm, and is now inland near the Mexico/Belize border heading W at 12kts. At this rate, it should enter the Bay of Campeche in the early morning hours (local) tomorrow, perhaps as a Depression. It is then forecast to regain TS status and head W into Mexico and make its final landfall early Saturday morning as a TS.

This is old news now, but I thought I'd share a high-resolution visible satellite loop that I made of Igor as a CAT4 on Sep 13 using 1-minute imagery: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/igor10/goes15_ch1_20102562045.swf

Please visit my tropical Atlantic headquarters.

Igor and Julia now both hurricanes, no threat to land...

2010-09-14T08:59:00.000-06:00

Igor has weakened slightly to 115kts/945mb, but is still a powerful Category 4 hurricane. During the night, the storm finally made a turn to the WNW, which models have been hinting at for a few days, but the storm wasn't doing it. Assuming this motion continues, this confirms that the storm is feeling the weakness in the subtropical ridge and will continue to turn toward it. Igor is expected to remain a major hurricane at least through this week. The primary land at risk is Bermuda, which could feel the worst of the storm late this weekend.

At 09Z today, Julia was upgraded to the 5th hurricane of the season. In an average season, the 5th hurricane would form around October 7, so we're certainly seeing an active season (the 2nd major hurricane hurricane would climatologically form around October 3, and we've already had 3!). At 15Z, the intensity was estimated at 75kts with a central pressure of 984mb. As is typical for pressures ~985mb, an eye is forming, and Julia is expected to strengthen more, until it hits higher vertical shear in a day or so. It's currently located about 355 miles WNW of the Cape Verde islands and heading WNW at 9kts.

The disturbance that was south of Jamaica yesterday is still not a Depression, and is located south of Isla de la Juventud, Cuba. The appearance continues to improve, and could become a Depression later today. There is a 1006mb Low associated with the disturbance, and the majority of forecast models intensify it to a TS prior to hitting the Yucatan, maintain or slightly weaken it during the crossing, then re-intensify it to a strong TS or weak hurricane as it traverses the Bay of Campeche. Landfall on mainland Mexico is expected on Saturday, assuming a storm actually forms. The next name is Karl.

Please visit my tropical Atlantic headquarters.

Igor now a CAT4 hurricane, Julia forms in far eastern Atlantic...

2010-09-13T09:26:00.000-06:00

Since my previous update on Saturday morning, Igor has become a very powerful Category 4 hurricane, with 130kt winds and a 933mb central pressure. The bulk of the intensification occurred on Sunday, when the pressure fell from 970mb to 942mb in 6 hours (and a corresponding increase in wind speed from 90kts to 120kts). Impressively, it has maintained Cat 4 status for a day now, and isn't showing signs of weakening yet. It's located about 880 miles east of the Leeward islands and heading W at 9kts. The forecast models have consistently been indicating a more NW turn in the track, which so far hasn't happened... in fact, it has been moving slightly south of west over the last 12-18 hours, which only one model (NOGAPS) was predicting. All models, even that one, are now showing a WNW-NW turn beginning almost immediately. There is quite a bit of model variance beyond 3 days, but it also isn't going to affect land any time in the near future.

The strong easterly wave that exited Africa on Saturday was promptly upgraded to TD12 then TS Julia (it was numbered at 21.4W, two degrees east of the easternmost Cape Verde islands... VERY far east!). It is currently located south of the westernmost Cape Verde islands, and the intensity is estimated at 35kts/1004mb. The forecast is for gradual strengthening, probably becoming the season's 5th hurricane, and for a NW turn in the track, taking it into the central Atlantic by 5 days.

The area of disturbed weather that was in the eastern Caribbean on Saturday has not gotten much better organized and is now south of Jamaica. It still has a chance to become a tropical cyclone in the coming days, as it's in a rather favorable environment. The track, if it forms, would be generally WNW into the Yucatan Peninsula then the mainland Mexican coast by the weekend. The next name on the list is Karl.

Please visit my tropical Atlantic headquarters.

Igor heading west, still a tropical storm...

2010-09-11T11:50:00.000-06:00

Tropical Storm Igor has gone through a few oscillations between sparse and healthy convection, but has maintained a vigorous low-level circulation. As of this writing, the deep convection is located over the center and is fairly symmetric. It appears to be taking advantage of an improving environment and is on its way to becoming the season's 4th hurricane. It's located about 1400 miles east of the Leeward Islands and heading W at 17kts. At 15Z, the intensity was estimated at 60kts and 995mb. The long-range forecast is for Igor to continue heading west, then make a gradual WNW bend by the middle of next week as it passes north of the Leeward Islands.

Two other disturbances are worth watching in the coming days: one in the far eastern Caribbean and one right on the African coast. Both of them are likely to become named storms in the coming days, and the next names are Julia and Karl. The easterly wave that is exiting the African coast is incredibly well-developed and could even be a numbered/named system before reaching the Cape Verde islands!

Also of note: today is the 50-year anniversary of Hurricane Donna's landfall on Florida (Category 4), and Hurricane Iniki's landfall on Hawaii (Category 4).

Please visit my tropical Atlantic headquarters.

Igor maintains intensity, easterly wave crossing Windward Islands...

2010-09-09T12:14:00.000-06:00

Igor is drifting around the Cape Verde islands in very weak steering, and the latest heading estimate is NNW at 5kts, but a general motion to the WNW is expected in the longer term. The deep convection is persistent, but not located over the surface circulation due to the rather strong (~25kts) vertical shear. However, the shear is forecast to drop drastically to about 5kts within the next couple of days and Igor should intensify and become the season's 4th hurricane. At 15Z, the intensity was 35kts and 1006mb. This storm is just off of Africa, so it will be a week or longer until it could even reach the Lesser Antilles, and much longer for any potential US encounter. Here is a map from Jeff Masters showing all past tracks taken by storms in the same location: http://icons-pe.wunderground.com/data/images/at201011_climo.gif

The easterly wave near the Windward Islands continues to get better organized, and is centered very close to Grenada (Grenada suffered catastrophic damage from Hurricane Ivan on Sep 7, 2004 and has barely recovered from that devastation). Luckily, this disturbance is nothing like Ivan, but will still bring flooding rains and perhaps tropical storm force winds to the area. Although poorly organized now, it must be watched very closely because the environment is quite favorable for significant development and forecast track scenarios for a storm in this location inevitably involve at least one landfall. The next name on the list is Julia.

I'd like to thank once again my guest writers during the past week, Kate Musgrave and Gus Alaka. I've heard from some of you that you were quite appreciative to keep receiving these updates in my absence!

Please visit my tropical Atlantic headquarters.

Hermine dissipating, Igor forms in the far eastern Atlantic...

2010-09-08T10:46:00.000-06:00

From Gus Alaka:

Tropical Depression Hermine (20 kts, 1005 mb) is located in central
north Texas and is bringing heavy rains to much of the state. Most of
the heavy rain occurred to the east of the center, as the onshore flow
helped feed moisture into the system. Much of the region received 3"+
of rain from 12Z yesterday to 12Z today. A few isolated areas (near
Austin, TX) received 10"+ during the same time frame. Hermine should be
extratropical by tonight.

1-Day Rainfall - Texas
<http://water.weather.gov/precip/save.php?layer%5B%5D=0&layer%5B%5D=1&layer%5B%5D=4&timetype=RECENT&loctype=STATE&units=engl&timeframe=current&product=observed&loc=stateTX>

****************************************

A vigorous tropical wave moved off the African coast yesterday. This
system maintained deep convection and the circulation became better
defined. Thus, Tropical Storm Igor, the 9th named storm of the 2010
Atlantic hurricane season, formed in the far eastern Atlantic,
approximately 95 miles SE of the southern Cape Verde Islands. The
initial intensity is set to (35 kts, 1005 mb) and it is currently moving
W at 7 kts. Igor is the 2nd tropical storm to form without first being
a tropical depression (Colin was the other). Presently, tropical storm
watches are out for the southern Cape Verde Islands of Maio, Sao Tiago,
Fogo, and Brava.

Igor's forecast calls for slow strengthening over the next couple of
days, with an increase in motion as it moves generally to the W. NHC
has Igor becoming a hurricane in 72 hours, which is slower than some of
the models, due to the presence of vertical wind shear. Igor is
forecast to turn to the WNW in a few days in response to a weakness in
the subtropical ridge. However, if the ridge does not weaken as
forecast, Igor could be of interest to the Leeward Islands in a week or
so, but let's not get ahead of ourselves.

****************************************
OTHER FEATURES

The remnants of Gaston continue to race through the Caribbean. Although
convection is present with the system, it is quite disorganized. Models
do not call for the redevelopment of this system.

Please visit my tropical Atlantic headquarters.

Earl makes landfall in Nova Scotia, Fiona dissipates, Hermine makes landfall in Mexico as a TS, remnants of Gaston entering the Caribbean, west African coast active again...

2010-09-07T12:27:00.000-06:00

From Gus Alaka:

Earl weakened from a Cat. 1 hurricane to a tropical storm and passed 
about 90 miles SSE of Nantucket Island, Massachusetts.  Most of the 
nasty weather associated with Earl was located to the east of the 
center, which allowed SE Massachusetts to escape mostly unscathed.  
Nantucket Island experienced gusts to about 55 mph and a few inches of 
rain.  Earl continued to race to the NE and made landfall at Western 
Head, Nova Scotia at 14Z on Saturday with (60 kt, 962 mb).  With a large 
wind field, much of the province experienced strong tropical storm force 
winds and heavy rain.  However, Earl had already begun an acceleration 
to the NE and did not linger long enough to cause any serious damage.  
However, Maritime Electric reported that 9400 Nova Scotian homes were 
without power at one point during the storm.  Earl quickly raced into 
the Gulf of Saint Lawrence, where it was pronounced extratropical at 3Z 
on 9/5.

Fiona continued to weaken and bear down on Bermuda late last week.  
However, the unfavorable environmental conditions got the best of the 
system, and Fiona degenerated into a remnant low before reaching 
Bermuda.  At the last advisory, Fiona was only 60 miles south of 
Bermuda.  The island likely experienced some gusty winds and isolated rain.

TD10 formed in the SW Gulf of Mexico late Sunday evening.  By Monday 
morning, TD10 intensified into Hermine, the 8th Atlantic tropical storm 
of 2010.  Moving generally to the NNW, Hermine intensified from (35 kt, 
1001 mb) at 9Z to (55 kt, 991 mb) at 0Z.  Hermine was still intensifying 
at landfall, and if the track had been slightly more N (rather than 
NNW), Hermine may have had a chance to become the 4th hurricane of the 
Altantic basin.  Hermine has since moved inland and will bring heavy 
rains (4"-8") and flooding to south Texas as the center moves to the N 
at ~15 kts.  Hermine, still a minimal tropical storm, is forecast to 
continue weakening and should be a tropical depression at the next 
advisory.

I was able to find this Doppler Radar image of Hermine at landfall:

There are no other named storms or depressions in the Atlantic.  
However, there are a few features of interest.

The remnant low of Tropical Storm Gaston is entering the NE Caribbean.  
There has been some convection associated with the remnant low, although 
NHC does not expect further development from this system.  To provide 
more support to NHC's assertion, a number of models (GFS, ECMWF, 
GFDL...) do not redevelop Gaston either.  Nonetheless, this system will 
be monitored for any signs of organization.

A potent tropical wave has just exited the west African coast.  It will 
be monitored for development as it travels W.

Please visit my tropical Atlantic headquarters.

Earl passes close to US coast...

2010-09-03T09:56:00.000-06:00

From Kate Musgrave:

Hurricane Earl passed east of NC early this morning as a Category 2 hurricane, before weakening further to a 75kt/961mb Category 1 hurricane at the 15Z advisory. Earl is currently located about 175 miles NE of Cape Hatteras, NC, or about 350 miles SSW of Nantucket, Mass. Earl continues to move NNE at 18kt and is expected to approach Cape Cod tonight as a hurricane, and reach Nova Scotia, Canada as a tropical storm tomorrow morning, before going extratropical in about 36 hours. Hurricane warnings remain in effect for parts of the Mass coast, with hurricane watches for parts of the southern coast of Nova Scotia. Tropical storm warnings range from NC to NJ, and parts of Long Island through portions of Mass, with tropical storm watches and warnings posted in Maine, New Brunswick and Nova Scotia. While Earl has weakened significantly, from 120kt to 75kt in 24 hours, the area covered by tropical storm strength winds is extensive, up to 205 miles from the center of the system.

Tropical storm Fiona has continued to recurve and weaken as it approaches Bermuda. As of 15Z it is 40kt/1010mb, moving NNE at 11kt. Fiona is expected to continue its weakening trend, dissipating within 3 days. It's center should pass closest to Bermuda in about 18 hours.

Tropical depression Gaston continued to weaken yesterday, dropping from a depression to a remnant low. The area will be monitored for possible redevelopment over the next few days. It is still expected to move to the W/WNW, approaching the Lesser Antilles in about a week.

Please visit my tropical Atlantic headquarters.

Earl approaching NC coast, Fiona turning towards Bermuda, Gaston is named...

2010-09-02T10:55:00.000-06:00

From Kate Musgrave:

Hurricane Earl has re-strengthened into a Category 4 hurricane, with its intensity at 15Z estimated at 120kt/932mb. Hurricane warnings continue on the NC coast and have been issued for parts of the Mass coast. Hurricane watches extend from the NC/VA border up through DelMarVa peninsula. Tropical storm warnings extend from the NC/VA border up to Mass, with tropical storm watches for parts of Long Island and extending from Mass up through Maine and parts of Nova Scotia, Canada. It is expected to weaken in intensity as it approaches the North Carolina coast, but still be a major hurricane at its closest approach overnight tonight/early Friday morning. Earl is expected to then accelerate and turn towards the NE, bringing it close to Mass by Friday night and then approaching Nova Scotia Saturday.

Tropical Storm Fiona has weakened slightly over the past day, and begun turning more to the N. As of 15Z it is estimated at 45kt/1002mb, moving NNW at 15kts. Fiona is expected to continue recurving to the N and NE, heading towards Bermuda. Tropical storm warnings have been posted for Bermuda. Fiona continues to deal with a much less favorable environment than Earl's, and the official forecast continues weakening Fiona before dissipating it in 4 days.

TD9 strengthened into Tropical Storm Gaston yesterday at 21Z, before dropping back down to a depression at 15Z today. It is currently about 1600 miles east of the Lesser Antilles and has slowed its forward motion. As of 15Z it is estimated at 30kt/1008mb, heading WNW at 6kts. It is expected to track WNW over the next several days and is still a week away from the Lesser Antilles, with the majority of models bringing it to hurricane intensity within that time.

Please visit my tropical Atlantic headquarters.

Earl still heading toward NC coast, Fiona affecting Leeward Islands, TD9 forms...

2010-09-01T09:05:00.000-06:00

Earl has weakened very slightly, and just happened to cross the Cat 3-4 threshold to 110kts (943mb central pressure). It's currently located about 725 miles SSE of Cape Hatteras, NC and heading NW at 14kts. Hurricane Warnings now cover all of the NC coast and Hurricane Watches cover the southern parts of the VA coast and the DelMarVa peninsula. The closest approach to the coast is expected early Friday morning, still as a major hurricane. Even if a direct landfall doesn't occur (meaning the center of the eye crosses the coastline), the western half of the storm, and perhaps even the eyewall, will affect land with flash flooding, strong damaging winds, and major beach erosion. Coastal areas from central NC up to Cape Cod can expect some storm surge, generally in the 2-5' range.

Tropical Storm Fiona has been improving in satellite appearance, but not drastically. It's approaching the northern Leeward Islands, but will steer away toward the NW before affecting them as much as Earl did 2-3 days ago. Its environment is much less favorable than Earl's was at the same location, and the official forecast actually weakens the storm to a Depression in 5 days as it recurves and heads n toward Bermuda. At 15Z, the intensity is 50kts and 998mb.

Elsewhere, an easterly wave that exited the African coast on the 28th has gradually been getting better organized, and has been upgraded to TD9. The majority of models develop this system into TS/Hurricane Gaston. It's about 1800 miles east of the Windward Islands, moving W at 13kts, and the intensity is estimated at 30kts/1006mb. It will track to the WNW over the next several days... still a week away from the Lesser Antilles.

I'd like to introduce a couple 'guest writers' who volunteered to send these updates out while I'm on vacation for the next week. Kate Musgrave and Gus Alaka, both very knowledgeable colleagues here at CSU, will keep you up-to-date with the activity across the basin. Thanks in advance to Kate and Gus!

Please visit my tropical Atlantic headquarters.

Danielle out of the picture, Earl heading for the US East Coast, Fiona forms...

2010-08-31T09:37:00.000-06:00

NHC ceased writing advisories on Danielle at 03Z as it completed its extratropical transition and entered the hurricane graveyard that is the north central Atlantic. It was a named storm for 10 days and didn't affect any land.

Earl, on the other hand, is still a powerful Category 4 hurricane and is finally moving away from the Leeward and Virgin Islands. There are radar loops (from 3 different sites) available at the link below. At 15Z today, the storm is located 1070 miles SSE of Cape Hatteras, NC and heading WNW at 12kts. The intensity is 115kts and 939mb, and is forecast to intensify further as it makes its way toward the east coast. The hurricane is undergoing a concentric eyewall cycle now, where a small eyewall gets replaced by a new larger eyewall over the course of about 12-18 hours. This can be a temporary disruption to intensification, but the end result is often a more intense storm than before. Hurricane-force winds extend 60 miles out from the center on the NE side of the storm, and the wind field will expand after the eyewall cycle completes.

The forecast is for Earl to remain a major hurricane for at least the next 3 days. Today and tomorrow it will brush by the eastern Bahamas, then head NW toward North Carolina. The official forecast keeps the center of the storm offshore, but not by much, and the distance is within the typical 3-day track forecast error. The closest approach (or landfall if that should happen) would be during the early morning hours on Friday. Even if the eyewall doesn't hit the coast, eastern NC will experience tropical storm and possibly hurricane conditions for several hours. After that encounter with the coast on Friday morning, eastern MA will be affected on Friday evening, then Nova Scotia on Saturday morning.

At 21Z yesterday, the easterly wave we've been tracking for a week was finally upgraded to TS Fiona, the 6th named storm of the season. Fiona is not in a very favorable environment, as as such, is not forecast to intensify much. It's currently 35kts, and located 440 miles east of the Leeward Islands. As I mentioned before, this system will affect the same islands that Earl just did, and there are already Tropical Storm Warnings and Watches for the northern Leeward Islands... again. The long-term forecast is for very slight intensification and recurving by 70W, not getting too close to the US east coast, but perhaps getting uncomfortably close to Bermuda this weekend.

Now that we're at the end of August, it's a good time to re-evaluate where the season stands compared to an average season. We have had 6 named storms, 3 hurricanes, and 2 major hurricanes. An average season by this date has 5 named storms, 2 hurricanes, and 0 major hurricanes.

Please visit my tropical Atlantic headquarters.

Danielle nearly extratropical, Earl becomes second major hurricane...

2010-08-30T09:32:00.000-06:00

Danielle continues to race toward to the north central Atlantic, rapidly losing tropical characteristics. The hurricane is located about 400 miles south of Newfoundland and the estimated intensity is 65kts and 970mb. Advisories on this system will likely be discontinued later today, though the extratropical Low is forecast to continue heading NE then recurve back to the NW and hit the southern tip of Greenland in 4-5 days.

Earl is now a 100kt Category 3 hurricane, and has been affecting the northern Leeward Islands for the past 18 hours and continues to do so. It has gotten to be a very powerful and impressive storm, and a clear eye is opening today on satellite imagery. At 15Z, the storm was located just 95 miles ENE of St. Thomas with an intensity of 100kts and a central pressure of 960mb. Hurricane Warnings are in effect for the Virgin Islands and the northernmost Leeward Islands... Hurricane Watch for Puerto Rico, and Tropical Storm Watch for eastern Bahamas (Turks & Caicos). Earl is forecast to recurve by 75W, which is a close call for the US east coast... and as I pointed out yesterday, the extremities of the coast should be cautious. A landfall on eastern NC (Thursday) or MA (Friday) is not out of the question, but also not very likely.

The easterly wave I've been mentioning for the past 5 days is still not classified as a Depression... it's been embedded in the same environment that Earl was for several days. The disturbance is located about 1300 miles east of the Lesser Antilles and heading W at 20kts. The system is analyzed with a 1007mb Low, and is still expected to become TD8/Fiona in the near future. Again, this track lies to the south of Danielle's and Earl's, and as such, poses a much greater risk for a US landfall (it would be at least 10 days out). It will also likely affect the same islands in the Caribbean that Earl just did.

Please visit my tropical Atlantic headquarters.

Danielle weakens, Earl becomes 3rd hurricane, still no TD8...

2010-08-29T11:08:00.000-06:00

Since my update on Friday morning, Danielle has recurved and weakened as forecast. The hurricane made a sharp turn to the NE well before reaching Bermuda, and is now accelerating and heading toward the cold waters of the north central Atlantic. At 15Z today, the intensity was 75kts and 976mb, and the heading was NE at 23kts. As it comes under the influence of the mid-latitude environment of colder SSTs and strong westerly wind shear, it will begin its extra-tropical transition, and is forecast to become fully extra-tropical by late Monday into Tuesday.

Earl, on the other hand, has finally entered a more favorable environment for intensification, and at 15Z today was upgraded to the third hurricane of the season with winds of 65kts and a central pressure of 985mb (and forming an eye). It's currently located about 225 miles east of Antigua and heading W at 15kts. A side-effect of not intensifying sooner is that it was steered by lower-level winds rather than mid-level winds that steer stronger storms, and has moved quite a bit further west without much of a northward component. This will bring the storm very close to the Leeward Islands and perhaps the eastern US seaboard. There are Hurricane Warnings for the northern Leeward Islands and Hurricane Watches for Puerto Rico and the Virgin Islands. The storm will affect these islands tonight into Monday as it likely intensifies into the second major hurricane of the season. The islands with the highest risk of hurricane-force winds are the northeastern-most, such as Antigua, the Virgin Islands, St. Croix, St. Eustatius, St. Kitts, Nevis, and especially Barbuda, Anguilla, St. Maarten, and St. Barthelemy.

As far as the track forecast is concerned, the majority of global and regional models do not indicate a US landfall for Earl, though it should be watched very closely because the latest consensus has the track halfway between Bermuda and the US coast, which is certainly with the 5-day margin of error. The "extremities" of the coast should be particularly watchful... areas like Cape Hatteras and Boston and northward to Nova Scotia and Newfoundland.

The easterly wave that exited the African coast on the 25th has still not gotten organized enough to be classified as a Depression. It's currently located at about 14N 39W and lacking persistent deep convection. However, nearly all models are forecasting significant intensification within 2-3 days, and more of a WNW track than Danielle and Earl took. Of the 3 storms, this "pre-Fiona" is the one with the highest US landfall risk. It's far too early to say where it would be, but in the shorter term, the track is forecast to remain to the south of the others, increasing the likelihood that it will not recurve as far east as the others. It's also quite likely to affect the same islands in the Caribbean that Earl is, so it will be a rough week for them (this encounter would be Wednesday-Thursday, just 3 days after Earl).

Please visit my tropical Atlantic headquarters.

Danielle becomes first major hurricane, Earl unchanged...

2010-08-27T12:00:00.000-06:00

In the overnight hours, Danielle rapidly intensified from 95kts/965mb to 115kts/946mb in just six hours. The intensity as of 15Z today is still 115kts and 946mb. This makes Danielle the first major (CAT3+) hurricane of the season. The satellite presentation is very impressive now... it is symmetric, with a clear eye and vigorous eyewall. Although this dramatic intensification wasn't forecast, the track has continued to 'behave'... recurvature is still expected to occur by 62W, keeping the worst of the effects east of Bermuda, though the island could still experience tropical storm conditions. Danielle is currently about 480 miles SE of Bermuda and tracking NW at 10kts.

Earl hasn't changed much in the last 24 hours... the intensity has held steady and the track forecast hasn't changed. It is currently a 40kt TS located about 1300 miles E of the Leeward Islands. The intensity forecast hasn't changed much either... it's still expected to enter a much more favorable environment in a few days and become the next hurricane, and perhaps major hurricane by the time it's north of Puerto Rico.

And, the easterly wave that was southeast of the Cape Verde islands yesterday has continued to get better organized and is now due south of those islands. Over the next several days, it is forecast to head WNW and develop quickly into a tropical storm, hurricane, and perhaps major hurricane. The next name on the list is Fiona. This time of year, having this burst of activity is quite normal.

Five years ago today, the first Hurricane Watch was issued for the LA coast in advance of Katrina's landfall. Coincident with that Watch being issued, a mandatory evacuation was ordered for the City of New Orleans, knowing that it's a very vulnerable area to storm surge (on the coast and below sea level).
http://www.nhc.noaa.gov/archive/2005/graphics/AT12/17.AL1205W.GIF
On the 28th, the storm reached Category 5 intensity and the following accurate forecast discussion came out of the New Orleans National Weather Service office:
http://en.wikipedia.org/wiki/National_Weather_Service_bulletin_for_New_Orleans_region#Bulletin_text
On the morning of the 29th, it made landfall as a Category 3 storm on the LA/MS border.
http://einstein.atmos.colostate.edu/~mcnoldy/tropics/katrina05/Katrina_29Aug05.gif

Please visit my tropical Atlantic headquarters.

Danielle and Earl continue to strengthen...

2010-08-26T10:37:00.000-06:00

Since yesterday, Danielle has entered a much more favorable environment and is now nearly a Category 3 hurricane with 90kt winds and a 970mb central pressure. It has also formed a large eye. It is heading NW as forecast and is still expected to recurve by around 62W, keeping it far from any land, with the exception of Bermuda, which could experience some turbulent weather and seas over the next few days.

Shortly after being classified as a Depression, TD7 was upgraded to TS Earl at 21Z yesterday. Earl has been struggling a bit with dry air, and remains a small and disorganized system. The latest intensity estimate is 40kts and 1004mb. However, it is expected to escape its poor environment shortly and begin a multi-day intensification trend, and many models indicate it will become a major hurricane in 5-6 days. It's currently located about 750 miles west of the Cape Verde islands.

Another large and relatively well-organized easterly wave exited the African coast yesterday. In visible satellite imagery, a low-mid-level circulation is evident near 10N 20W (southeast of the Cape Verde islands). The majority of global forecast models develop this system, so it will likely be the next named storm, Fiona, in a few days.

Please visit my tropical Atlantic headquarters.

Danielle maintaining intensity, TD7 forms...

2010-08-25T08:54:00.000-06:00

Due to an intrusion of dry air that interrupted the intensification of Danielle, the storm has barely strengthened in the last 24 hours. The intensity as of 15Z today is 75kts and 982mb. It appears to be recovering now and should be on another intensification trend. Model guidance suggests the storm could reach Category 3 status in 2-3 days before it heads too far north and over colder water.
The latest forecast shows Danielle recurving by 62W, not affecting any land.

The easterly wave that exited the African coast on Monday has been upgraded to TD7 today based on satellite presentation. It's quite well organized and could easily become TS Earl later today. Models are in very good agreement that this system will develop fairly rapidly, becoming the third hurricane of the season within 2-3 days as it heads WNW. On that track, is should be just NE of the Leeward Islands by early next week.

Please visit my tropical Atlantic headquarters.

Andrew's anniversary, Danielle becomes 2nd hurricane, eastern Atlantic still active...

2010-08-24T08:07:00.001-06:00

Today is the 18-year anniversary of Hurricane Andrew's catastrophic landfall near Miami. The eye crossed the coastline at Homestead with a pressure of 922mb. Wind measurements are uncertain, as nearly all anemometers were destroyed, but the strongest gust observations that exist are around 175mph.
http://en.wikipedia.org/wiki/Hurricane_Andrew
http://www.nhc.noaa.gov/gifs/1992andy.JPG
And, here are some very nice radar loops saved by my friend and hurricane chaser Michael Laca in Miami: http://www.youtube.com/watch?v=ZgoqyumbXLE

At 21Z yesterday, Danielle was upgraded to a hurricane, the second of the season. The storm has continued to intensify, now a Category 2 storm with 85kt winds and a 973mb central pressure. It is forecast to reach major hurricane status later today and tomorrow. The track forecast has not changed... still heading WNW then beginning to recurve by 60W.

The easterly wave just off the coast of Africa has also gotten better organized, though isn't quite a Depression yet (as of 14Z). Its estimated intensity is 25kts and 1008mb. It is expected to develop quickly, and most likely become the 3rd hurricane of the season in a few days as it heads WNW. The next name on the list is Earl.

Please visit my tropical Atlantic headquarters.

TS Danielle nearly a hurricane...

2010-08-23T09:10:00.000-06:00

Since my last update on Saturday morning, TD6 was upgraded to TS Danielle on Saturday evening. The storm has continued to organize, and is forming an eye (already evident in microwave imagery, and beginning to appear in visible and infrared imagery). It is nearing hurricane intensity, currently at 55kts and 994mb (and located about 1000 miles west of the Cape Verde islands). It will likely be a hurricane later today.

The global models not only did an exceptional job at forecasting Danielle's development nearly one week in advance, they also did a fine job at predicting a recurvature by 60W, which is still on target to come to fruition. Although still one week away, recurvature is forecast by all of the global and regional models. That certainly won't hinder Danielle reaching hurricane status, and perhaps major hurricane status.

Elsewhere, a new potent easterly wave has just exited the African coast today, but surprisingly, the majority of models do not develop that disturbance. If it should "go", it would likely follow the same track as Danielle since the large-scale steering hasn't changed much.

Please visit my tropical Atlantic headquarters.

TD6 forms from east Atlantic disturbance...

2010-08-21T15:00:00.000-06:00

At 21Z today, the easterly wave that I have been discussing for the last few days near the Cape Verde islands was upgraded to TD6, and the latest estimated intensity is 25kts and 1008mb. It's southwest of the Cape Verdes now, at about 11N 32W and heading WNW at 8kts. Given the favorable environmental conditions in its present location and along the forecast track, the storm is expected to develop rather quickly, reaching Tropical Storm intensity early tomorrow and hurricane intensity by Monday afternoon. Models are in good agreement on the intensification scenario, and on continuing a WNW track for the next few days. At 5-7 days out, it currently appears that the storm (Danielle is the next name) will recurve into the open Atlantic by 60W.

Please visit my tropical Atlantic headquarters.

Disturbance off Africa getting better organized...

2010-08-20T09:44:00.000-06:00

The easterly wave I mentioned yesterday is now slightly further west than it was, but still generally south of the Cape Verde islands. The visible satellite imagery reveals a rather well-developed surface and mid-level circulation centered near 11N 26W. The latest surface analysis indicates a 1008mb Low associated with the disturbance. It's in (and will remain in) a very favorable environment with low vertical wind shear and 28C SSTs.

In the coming days, it will continue its WNW heading and probably become a Depression, tropical storm, and hurricane this weekend into early next week. The majority of global forecast models indicate possible recurvature by 60W, which would preclude any landfalls, but it's too soon to be certain about that. The next name on the list is Danielle.

Please visit my tropical Atlantic headquarters.

Large easterly wave exits Africa...

2010-08-19T09:25:00.000-06:00

A very large, broad, easterly wave is located just south of the Cape Verde islands, with a disorganized low-mid-level circulation at about 12N 25W (easy to spot from the 07:25Z WindSat and 10:55Z ASCAT microwave scatterometer overpasses). It exited the coast about a day ago, and already has a weak anticyclone positioned over it, greatly reducing the vertical shear and enhancing outflow.

Nearly every global model develops the system substantially, bringing it northeast of the Lesser Antilles (roughly 20N 55W) as a hurricane in about a week.

I've been asked by a few people why the season has been so quiet so far. In reality, it hasn't been; it's been on par with climatology... by this date, an average season has had 3 named storms, 1 hurricane, and 0 major hurricanes, which is exactly what 2010 has seen. Given the continued favorable environment across most of the basin though, once the heart of the season is upon us (very soon), people will be asking why there are so many storms! The bulk of a season's activity typically comes in a relatively short timeframe: http://www.nhc.noaa.gov/gifs/peakofseason.gif.

Please visit my tropical Atlantic headquarters.

Systems brewing over southern Florida and in central Atlantic...

2010-08-10T09:49:00.000-06:00

A very large mid-upper-level Low that has been sitting over southern Florida is getting better organized and apparently developing a surface circulation based on surface and satellite observations. There are widespread thunderstorms associated with the 1010mb Low which is drifting to the WNW. The center of the circulation is just off the southwest FL peninsula, and is visible from the Key West radar: http://radar.weather.gov/radar.php?rid=BYX&product=N0Z&overlay=11101111&loop=yes
The forecast is for this to continue developing... reaching tropical storm intensity as it heads into the LA coast by late Thursday.

The other area of interest is the one I mentioned back in my last update on the 6th... it is now in the middle of the basin, about 800 miles ENE of the Leeward Islands. It is in a strongly sheared environment and although it has persistent deep convection, it's all northeast of the low-level center. Many forecast models do bring it up to TS intensity soon, and recurve it in a day or so, taking it out to the far north central Atlantic (i.e. tropical cyclone graveyard).

At this point, it's hard to say which of the systems could get named first, but if they both do, the next names on the list are Danielle and Earl.

Please visit my tropical Atlantic headquarters.