29 December 2012

Second Rainiest Year for Miami

This is a little off-topic from the usual hurricane updates, but I thought it was an interesting tidbit from the hurricane hotspot of Miami.  I hope you find it interesting too!

When you think of southern Florida, you think of a tropical climate... with year-round warm weather, exotic flora and fauna, beautiful beaches that seem to go on forever, and copious amounts of rain. So when a tropical location like Miami nearly breaks its all-time record annual rainfall total, that's really a LOT of rain.

There are essentially just two seasons in Miami: the drier cooler winter (approximately November through April) and the humid hot summer (approximately May through October). Climatologically, about 75% of the city's rainfall comes during the summer, and the average annual total rainfall is 61.9”. This map shows the average precipitation across the country so you can find your favorite city (the averages used throughout the post are the standard 1981-2010 “climate normals”, and the rainfall amounts listed for Miami are from the Miami International Airport).

This year, while a huge portion of the country suffered from extreme drought conditions, Miami got off to a wet start, and it just kept coming. By the beginning of April, Miami was at 125% of average rainfall, and by the beginning of July, up to 174% and the second wettest year on record for the January through June period. For the January through September period, Miami's 2012 total rainfall was 79.5”, the wettest such period on record by a healthy margin. At year's end, it's at 86.94”, or 140% of average... very close to breaking the record of 89.33” set in 1959.  By the way, 87" is 7'3" for those who think better in feet.

The chart below shows these periods and annual totals graphically going back to 1949*. The annual total is shown in cumulative quarterly increments. The first three months are denoted by the purple bars, the first six months by the green bars, the first nine months by the yellow bars, and finally, the full year by the top of the red bars.
Zooming in to just 2012 and plotting the daily cumulative rainfall amounts against the climate normal clearly shows that from May onward, Miami remained well above average, and frequent events maintained and grew the gap.

* 1949 is used as the start of the data period due to availability and station relocation.  See the first data source below. 
Data sources:

28 November 2012

2012 Atlantic hurricane season summary

To those who have been subscribed and reading my posts since the humble beginnings in 1996, I want to thank you for your continued support and interest.  And to the many more recent readers, thanks for joining!

I have sent out approximately 850 tropical updates over the years.  Those updates have spanned 252 tropical storms, 114 hurricanes, 58 major hurricanes, and 36 retired storm names.  WHEW... my fingers are tired just thinking about that!

My season summary to wrap up the 2012 hurricane season is now available on the Washington Post's Capital Weather Gang blog, and again, thanks for reading!

02 November 2012

30 October 2012

Superstorm Sandy managed to live up to the hype

For many, Sandy certainly lived up to the seemingly impossible forecasts of impacts. For starters, it made landfall with a central pressure of 946mb... the second lowest pressure ever recorded for any storm to hit the northeastern U.S. (first place was the 1938 Great New England Hurricane at ~941mb).  Maximum sustained winds were 80mph, and higher gusts were reported from Rhode Island down to North Carolina.

The center came ashore near Atlantic City NJ around 8pm EDT last night, though its effects were of course felt far from the center.  This satellite image shows Sandy at landfall on Monday evening.

In terms of a human toll, 84 lives have been taken by the storm (as of 9am today) across the Caribbean, the U.S., and Canada.

At least 7.5 million people in the northeast are without power.  The only silver lining there is that the temperatures after the power outages aren't sweltering or frigid, so it's generally not as life-threatening as it could be.

The Battery in downtown NYC ended with a peak water level of 13.88', which is about 2'8" higher than the previous record (set in 1821).  That, of course, resulted in a total catastrophe.  By around 8pm, the subways and automobile tunnels were filling with sea water.  And before that, both JFK and La Guardia airports had flood water pouring across the runways and into the terminals.  The flooded areas of NYC also experienced large fires, collapsed buildings, and the power company shut off electricity to the city before the flooding got too bad and damaged the equipment.  The iconic fishing pier at Ocean City MD has been completely destroyed.  The streets of Wildwood NJ became the beach as the storm surge inundated the huge beach they used to have.  The Atlantic City boardwalk is now rubble and the city flooded.  The full range of impacts across all of the states are too numerous to detail here, but you will undoubtedly see and read more in the news.

A buoy at the entrance to the New York Harbor recorded a peak wave height of 32.5 feet... but I'm not yet aware of what affects such large waves had on the immediate area.

As of this morning, the Potomac River reached its highest level since 1996 due to the heavy rainfall.  5-7" of rain fell in much of Maryland, Delaware, and northern Virginia; southern New Jersey received about 7-9", northern New Jersey saw about 2-4", while much of southest Pennsylvania was in the 3-5" ballpark.  Meanwhile, it's still snowing hard West Virginia and they are expecting 2-3 feet of very wet snow.

It's not over yet either.  Heavy rain is still falling over an enormous area, and storm surge and coastal flooding continues to be a very large danger.  This image shows the current radar depiction of the precipitation still affecting 17 states.  I also have very long radar loops covering Sandy available at http://andrew.rsmas.miami.edu/bmcnoldy/tropics/radar/

Sandy will certainly be a storm for the record books, and will also end up being a retired name.  Going back to 1953, the only storms so late in the alphabet to be retired were Stan (2005), Wilma (2005), and Tomas (2010).

29 October 2012

Sandy's historic landfall expected tonight

Hurricane Sandy continues to loom ominously off the U.S. east coast, bringing very heavy rain and tropical storm to hurricane force winds to many millions of people well before the worst arrives. The coastal flooding is already terrible, as expected (even as far south as Miami and Fort Lauderdale!). Locations from North Carolina to Maine will continue to see incredible coastal flooding/erosion, with the worst near and north of where the center crosses land (approximately southern NJ into NYC, Long Island, CT, RI, and MA). Inland flooding will also be a large problem in the coastal states as well as the inland states throughout the northeast. Finally, the 50-90mph winds that many places will experience can easily damage roofs, break tree limbs, and uproot trees, bringing power lines down with them.

At 8am EDT today, Sandy was a Category 1 hurricane with 85mph sustained winds, and a 946mb central pressure (it's that very low pressure that creates the strong winds at the surface).  The wind field is so large that tropical storm force winds (45mph+) extend 485 miles out from the center.  The center is located approximately 300 miles south of NYC and 300 miles east of Norfolk... heading for a landfall late tonight near Atlantic City.  I have multiple long radar loops available at http://andrew.rsmas.miami.edu/bmcnoldy/tropics/radar/index.html#sandy12

Perhaps the trickiest part of this system from a warning perspective is that Sandy may not technically be a hurricane by the time it reaches the coastline later tonight. It is interacting with a cold front that is draped on the coastline and is losing some of its tropical characteristics. It actually has a warm front forming off to its east and a cold front to its south... a sign that it's transitioning to an extratropical cyclone.

This absolutely does not make it any less dangerous! It has been intensifying (by both tropical AND extratropical mechanisms), and this interaction with the mid-latitude front is exactly what has been forecast to occur for days now. With or without a hurricane or a hurricane warning, this storm is extraordinary, unprecedented, and must be taken very seriously.  The storms it has been compared to are the 1938 Great New England Hurricane, Hurricane Gloria in 1985, and the "Perfect Storm" of 1991.  Sandy will join this crowd, and likely surpass some (if not all) of them in total impacts and damage.

This is truly a worst-case scenario that will cost tens of billions of dollars and claim hundreds of lives.  Huge unthinkable storm surges along the entire northeast U.S. coast (particularly in the New York City and northern NJ region), mostly reaching their worst at night and during a full moon (already higher-than-normal tides), large rainfall amounts over several states, 2-3 FEET of wet snow in the mountains of WV, and widespread power outages for perhaps 10 million people.

If you're in the affected areas, be aware of nearby streams/creeks/rivers that could quickly turn into white water rivers... large trees near your house... and be prepared to lose power for several days.  Also, remember to check up on family and friends who might be at a higher risk than you.

A good source of constant updates through the coming couple of days is the Capital Weather Gang's live blog... and for the latest local bulletins and warnings, check your local National Weather Service office.

22 October 2012

16 October 2012

Hurricane Rafael heading toward Bermuda

At 03Z today (11pm EDT last night), Rafael was upgraded to the season's 9th hurricane.  At the 21Z advisory, the central pressure was 985mb with 60kt sustained winds, then at the 03Z advisory, it was 974mb and 75kts.  Both advisory intensities were supported by aircraft measurements.  The last time a storm had such a low pressure at its first advisory as a hurricane was Alex in 2010 (973mb).

The satellite appearance is not the best anymore, but as of 11am EDT today, the intensity is 75kts and 971mb.  It is expected to gradually weaken over the next couple of days until it transitions to an extratropical cyclone.  It is forecast to make its closest approach to Bermuda later tonight as a hurricane, and the center should pass just 100-150 miles east of the island.

Rafael is already in radar range from Bermuda now, and you can find a growing radar loop at http://andrew.rsmas.miami.edu/bmcnoldy/tropics/radar/

15 October 2012

Rafael almost a hurricane

Since my previous post on Friday, Patty got smothered by the mid-latitude trough and front as expected, and the final advisory was written on it on Saturday morning. 

Meanwhile, the disturbance that left the African coast on October 5 was upgraded to Tropical Storm Rafael on Friday night based on aircraft reconnaissance.  This is the same wave that I mentioned last Thursday when it was east of the Lesser Antilles.  It is now about 350 miles due north of Puerto Rico, and is just shy of becoming a hurricane (should be later today).  This would make Rafael the 17th named storm and the 9th hurricane this year in the Atlantic. [We've still only had 1 major hurricane very briefly: Michael.  The last five seasons with 0 or 1 major hurricanes were 1990, 1992, 1993, 1994, and 1997.  So it's been a while, but the season isn't over yet...]

At the 11am EDT advisory, the maximum sustained winds are 60kts with a 985mb central pressure.  Tropical storm force winds extend 205 miles from the center.

The traditional satellite presentation is quite impressive, and in earlier overpasses by microwave instruments, it already has an eyewall and eye below the cloudtops.  I'm going to include a couple images to showcase some of the noteworthy features.  The first is a full-resolution visible image from GOES-14 zoomed in right over the storm.  The fine whispy cirrus outlow exists in all quadrants except the northeast, and the deep intense thunderstorms are firing up and wrapping around the center.  Then, in the enhanced infrared image below that, you can see the temperatures of the cloud tops, with the coldest highest cloud tops in black and light gray and the warm ocean on the other side of the scale, also in dark gray.

Assuming it does indeed become a hurricane later today, it would be the first hurricane we've had below 25N since Ernesto (briefly a hurricane in early August before hitting the Yucatan peninsula).  And even Rafael would sneak in below 25N by a very small margin.  That is certainly an oddity of the season!

Track models are all in very good agreement that Rafael will head north toward Bermuda, then gradually turn northeast, most likely passing slightly east of Bermuda on Tuesday evening before racing into the cold and hostile north central Atlantic.

It probably won't be able to strengthen too much more, but should remain in the 65kt ballpark (+/- 10kts) for the next few days before turning extratropical.

Elsewhere, there's nothing on the horizon, but this time of year, we need to keep a closer eye on the western Caribbean and Gulf of Mexico for quick developers.

11 October 2012

Two disturbances to watch across the basin

The first disturbance is an easterly wave that left the African coast back on October 5, and has been making its way westward.  It's now centered near 11N 56W (about 340 miles east of Grenada in the southern Lesser Antilles) and has an embedded 1007mb Low.

Fortunately for North American interests, models are in good agreement on this system turning to the north very soon, probably passing east of Puerto Rico (rather similar to Jose 1999). One exception is the ECMWF global model, which has a more northwest track, bring it over Puerto Rico, then the Bahamas, THEN recurves it on Monday over the Bahamas before it reaches Florida.

As far as intensity goes, it has a good chance at becoming a Depression and then Tropical Storm in the next few days, but then the vertical shear is forecast to become fairly hostile after about 3-4 days, putting a brake on whatever intensification might be happening.  The next two names on the list are Patty and Rafael, and depending on the timing of this disturbance and the next one I'm going to talk about, this could be either.

The second disturbance has been a trackable entity since about October 6, and appears to be very close to Depression status (I think it has been a Depression for a while already, but NHC hasn't officially upgraded it).  However, it now has less than a day to "make its move" because a large frontal boundary is encroaching on it and will envelope it shortly.  On the large-scale water vapor image shown here, the disturbance in question is the blob of purples north of Hispaniola (the bright colors denote cold cloud tops and higher upper-level humidity, while the browns and blacks denote much lower humidity in the upper-levels).  Being that close to a mid-latitude trough/front is bad news if you're a tropical cyclone.

An enhanced satellite image with a closer view of the system shows the two air masses very clearly.  In the low-level clouds (yellow), two features are worth pointing out: 1) the surface Low is mostly exposed and centered to the southwest of the deep convection (white), and 2) the frontal boundary between the warm moist tropical air and the cooler drier mid-latitude air is evident and runs southwest to northeast... very close to the disturbance/depression.

04 October 2012

Latest on Nadine, Oscar, and GOES-East

Just a short update today, since both named storms are weak and far from land.  The enhanced satellite image below shows the locations of the two systems marked with a red "O" and "N". 

This map shows the past, current, and forecast tracks of both storms... Nadine (AL14) over the Azores, and Oscar (AL15) south of the Azores.  Both are expected to become post-tropical within a day or so.

Nadine continues to lose its identity and is expected to become fully absorbed by a mid-latitude trough later today.  Depending on exactly when the plug is pulled, it will end up at about 22.5 days as a numbered system, which is enough to put it in fourth place for longevity in the Atlantic since 1851.

Shortly after my update yesterday, TD15 was indeed upgraded to Tropical Storm Oscar, the 15th named storm of the season.  As I pointed out in a previous post, historically, only about 8% of seasons ever reach the 15th named storm, so this is certainly impressive, but about a month too late to be considered for the record earliest formation date of the 15th named storm.

Today is the twelfth day since GOES-13's primary instruments failed, and the fourth day since GOES-14 has been allowed to drift eastward to take over the GOES-East "parking spot" at 75W (so today it would be centered over 102.3W).  For details on this manuever and the relative locations of the satellites, please see the last section in yesterday's post

02 October 2012

As Nadine fizzles, Oscar may be forming

Stubborn Nadine is still a strong tropical storm with 55kt sustained winds, and is expected to remain a tropical system for another couple of days before finally getting obliterated by a mid-latitude trough.  It has been on the books for 20 days... in yesterday's post I highlighted the longevity record holders for reference. 

One thing a storm does when it sits over the same area for a long time is upwell colder water from the depths of the ocean.  In some places, the surface water might be warm, but that warm water doesn't extend very deep, making it easy for a storm to mix it out.  Nadine has been in the vicinity of the Azores for a couple weeks now, and has generated quite a patch of anomalously cold water as shown here.  A 2-degree Celsius anomaly is pretty significant, and greatly reduces the potential intensity of a storm.

As you can see in the satellite image below, it is a respectable tropical cyclone with an eye, indicating that it remains well-organized... the Azores islands are the yellow outlines on the right side of the image.

Now, there's another disturbance getting organized.  It's an easterly wave that left the African coast back on September 28, and is now centered near 12N 39W (about 850 miles west of the Cape Verde islands) with a 1009mb central pressure.  It appears to be on its way to becoming Tropical Depression 15 and then Tropical Storm Oscar this week.

The majority of models do intensify this to a hurricane, but also agree on a sharp turn to the north very soon, keeping it far away from land.  Oh, and if you're in the Azores, you might get another tropical visitor this weekend... as if the current guest hasn't already overstayed its welcome.

Assuming it gets named this week, it will be the 15th named storm of the season.  That is impressive, but far from a record.  In 2005 and 2011, we saw the 15th named storm form on September 7, and then in 1936, the same thing on September 19.  However, only about 8% of years ever reach the 15th named storm, so it's still an outlier in that regard.

01 October 2012

October Ushers in Highest Likelihood of Hurricanes in South Florida

Today's update includes the latest on Nadine, Nadine's longevity, the drought of U.S. major hurricane landfalls, and a focus on south Florida's hurricane climatology.

You can read today's post on the University of Miami's RSMAS blog.  Thanks for reading!

28 September 2012

Nadine back up to hurricane intensity

Today's update actually focuses more on a noteworthy storm in the West Pacific ocean (Typhoon Jelawat), but also provides the latest on re-upgraded Hurricane Nadine.

The update can be found on the Washington Post's Capital Weather Gang blog.  As always, I appreciate your continued interest!

24 September 2012

Zombie storm haunts the north Atlantic

An easterly wave that exited the African coast on September 7 became TD14 on September 11.  It was upgraded to Tropical Storm Nadine just twelve hours later, and then Hurricane Nadine on September 15.  The "final" advisory was written on it this past Friday night, but 36 hours later, it came back from the graveyard, and is now a tropical storm again, and may become a hurricane... again.  So, as I mentioned a week ago, we'd still be talking about Nadine for quite some time!

At 09Z today (5am EDT), Nadine's estimated intensity was 45kts, and forecast to slowly intensify to a 65kt hurricane by the end of the week as it drifts westward.  In the image shown here, you can see the Azores to the north of the storm (yellow outlines) and an underwhelming satellite appearance.

Aside from Nadine, the basin is quiet, which is extremely fortunate because the primary "eye in the sky" failed on Sunday afternoon.  I'm referring to GOES-13, NOAA's operational geostationary satellite that provides continuous satellite images over the eastern US and Atlantic basin.  The satellite was launched in 2006, and was held in reserve until its predecessor failed in 2010.  So it's only been in operation for 2 years... not a good record.  It's possible that it can be fixed, but it would need to be by clever electrical engineers on the ground, since physically repairing it is not an option.  There is a spare satellite parked in orbit for exactly this scenario (GOES-14), but before pulling it out of storage, GOES-15 (the western operational satellite) will be used in full-disk mode to provide some coverage.  The GOES-15 view of the basin looks like this:

These geostationary satellites (named that because the satellite orbits the earth at the same rate the earth rotates, so it's always looking down at the exact same spot on the globe) must orbit at an altitude of 22,236 miles above the Earth's surface at the equator.

19 September 2012

Tropical storm conditions continue in the Azores

As expected, Tropical Storm Nadine has virtually stalled near the Azores, and isn't planning on moving out any time soon.  The enhanced satellite image below shows the high clouds associated with outflow or thunderstorms in white, while low shallow clouds appear yellow, and the ocean is dark blue.  The Azores islands are the purple outlines northeast of the storm's center.

[The Azores is an archipelago comprised of nine volcanic islands.  Six hundred years ago, these islands were uninhabited, but now are home to a quarter of a million Portuguese residents.  ]

At 09Z today, Nadine had 45kt maximum sustained winds with a 993mb central pressure.  It's crawling north at 4kts, and is forecast to gradually drift eastward over the next 5 days... leaving the Azores exposed to tropical storm conditions for around a week.  Luckily, it's not very intense, and there's limited rainfall on the eastern side lately.  But the 26' waves being reported at Santa Cruz (western part of the islands) are impressive.

As far as HS3 is concerned (NASA's big field program: Hurricane and Severe Storm Sentinel), today is a huge media day at Wallops Island where the unmanned aircraft is based.  The Global Hawk is scheduled to depart around 2pm EDT today for a 26-hour flight over Nadine, releasing 79 dropsondes over and around the storm in a "lawnmower pattern" to survey the environment.  The proposed flight path is shown here for reference.

The Azores is no stranger to tropical cyclone encounters.  They're in a fairly common path for recurving storms, and they don't always just get the "leftovers"... some encounters have been with potent hurricanes.  This map shows the tracks of the 23 storms that have passed directly over the Azores in the past 160 years.  In order to count, the center of the storm had to pass within 230 miles of the middle of the Azores and be at least a tropical or subtropical storm (depressions and extratropical systems aren't included).  Now the map will include Nadine!

Elsewhere, the basin is quiet during this climatologically active week.

17 September 2012

Nadine heading for the Azores

Over the weekend (03Z on Saturday), Nadine reached an intensity of 70kts, making it the season's 8th hurricane.  After a couple days, it weakened back to a tropical storm, but just barely.  At 15Z today, it's a 60kt tropical storm (at 65kt, it would be a hurricane, so it's a fine line between two different classifications) and heading ENE at 15kt toward the Azores islands.  In the image shown here, shallow clouds appear yellow, while deeper clouds (tops of thunderstorms or outflow) appear white.  From this, it's evident that the storm is becoming asymmetric and losing its centralized deep convection.

Models agree that a significant slow-down should occur, and in five days, we'll still be talking about Nadine near the Azores!  In fact, most guidance is showing a re-recurvature when Nadine reaches the Azores... coming back toward the southwest and possibly re-intensifying.  Recall that the first advisory was issued for Nadine (TD14 then) on the morning of September 11, and the last could still be at least a week away!

The official track forecast from NHC has the storm centered over the Azores in 5 days... as a tropical storm.

Elsewhere, the basin is abnormally quiet for mid-September.

In terms of ACE, the season has slipped to 134% of average for this date.  As I mentioned on Friday, every day without a hurricane (or major hurricane, or multiple hurricanes) this time of year is "behind" an average day.

14 September 2012

Nadine recurving as Global Hawk surveys its environment

Nadine has been on the TS-hurricane threshold (60kts) for about 36 hours now, and probably won't change much in the coming days as it recurves to the north and begins its extratropical transition. 

Track guidance is in good agreement on a path toward the Azores in about 6 days, perhaps as a hurricane, perhaps as a tropical storm, or perhaps as a potent extratropical storm (somewhere in the 50-70kt ballpark by the time it reaches the islands).  The NHC 5-day forecast is shown by the thick green line, while various models are shown by the thin multi-colored lines.  The Azores islands are labeled for reference.

The big NASA field program, HS3, is sending the Global Hawk unmanned aircraft to survey Nadine today, releasing 69 dropsondes in a 15x15 degree "lawnmower pattern" around the storm to get a detailed picture of the near-storm environment.  The state-of-the-art plane took off from Wallops at 10:00am EDT this morning, and will fly over Nadine until tomorrow morning at 6:15am.

Aside from Nadine, the basin is amazingly quiet for the second week of September.  There is an easterly wave centered right on the African coast that some global models (e.g. GFS and FIM) develop ever so slightly, while the others show it doing nothing.  We certainly have time to watch it and see if it's worth another mention.

The ACE (Accumulated Cyclone Energy) stands at 80.6 as of this morning, which is about 139% of what an average season would be at on this date.  This time of year, every day without a hurricane (or multiple hurricanes for that matter) lets 2012's ACE loose ground against the average because climatologically, ACE racks up real fast in mid-September.  We're very close to the ACE we had in 2010 and 2011 on this date.

12 September 2012

Nadine forms and becomes season's 14th named storm

At 03Z today (11pm EDT Tuesday night), TD14 was upgraded to TS Nadine.  It's quite extraordinary to have the 14th named storm occur on September 12th!!  As I mentioned a couple of days ago, I was only able to find two other years in 160 years of record-keeping in which the 14th storm formed sooner: 1936 and 2011.  I'm going to include a far-view satellite image as well as a full-resolution image (1km) from GOES-East... just because they're so pretty!

At 15Z today, Tropical Storm Nadine's maximum sustained winds are at 50kts, and it's most decidedly on an intensifying trend.  The NHC forecast brings it up to a hurricane (the season's 8th) by Thursday morning.
The track model guidance continues to be very closely bundled, and shows a recurvature by the time it reaches 55W, keeping it safely away from any land encounters.  Although it is in a healthy environment now, its time is limited, as strong vertical shear is in its future.

The graph below shows the forecasts of intensity, track, shear, SST, and mid-level humidity from a few key models.  You can see the expected intensification in the near future, but then the dramatically increasing shear, the decreasing SST, and the decreasing RH... all working together to keep Nadine from becoming an extremely intense hurricane.

This storm is also being throughly probed by unmanned aircraft as part of NASA's huge field program called "Hurricane and Severe Storm Sentinel", or HS3.  A centerpiece of the program is the Global Hawk, a highly advanced unmanned aircraft capable of flying very long missions, and it carries with it a large suite of instruments and dropsondes to send high-resolution enviromental data into operational computer models.  Check on the Capital Weather Gang's blog later for a more detailed description of this program and its activities with Nadine!

10 September 2012

Peak of season comes with Hurricane Michael, TS Leslie, and almost-TD14

Today is the climatological peak of the Atlantic hurricane season.  On average, this is the date when you're most likely to have tropical cyclone activity, and 2012 is no exception.  In fact, we nearly have one of each flavor!  We're extremely close to having Tropical Depression 14 in the eastern Atlantic, Tropical Storm Leslie north of Bemuda, and Hurricane Michael west of the Azores.

In this graph, the red curve represents tropical storm activity, while the yellow is for hurricanes.  There are still 81 days left in the official hurricane season, which ends on Nov 30.

Group photo of Leslie, Michael, and TD14-to-be.


Leslie never did reintensify to a hurricane, and passed 150 miles east of Bermuda on midday Sunday as a strong tropical storm.  The strongest sustained wind I could find on Bermuda was 34kts, with gusts to 47kts.  I'm including a radar image from when Leslie was at its closest approach.  The full long loop can be found here.

It is now on its way toward Canada... a hurricane watch and tropical storm warning have been issued for eastern Newfoundland. 


Michael has very slowly weakened, but is still hanging onto hurricane status.  It's a 70kt Category 1 storm now, and is forecast to become extratropical by Wednesday.  It has been a hurricane for four days now, which isn't bad considering its dismal extratropical origins.  It's presently about 1100 miles west of the Azores and heading W at 7kts.


The easterly wave that exited Africa on the 6th did indeed get organized in a hurry, as models predicted.  It will soon become TD14, and is located about 1500 miles east of the Lesser Antilles.

Models are in excellent agreement on the track, and show it heading WNW for the next couple days, then recurving by the time it reaches about 55W (a track in between Kirk's and Leslie's).  They also agree on this becoming TS Nadine very soon, then a hurricane in 3-4 days.  It will not be a threat to land.


In terms of ACE (Accumulated Cyclone Energy), we're now at 78.6 compared to the climatological value of 49.6 for this date... that's 158% of average!  And, we're going to soon see the 14th named storm this week, which is also quite amazing.  Only about 10% of years ever reach the 14th named storm, and this year, that should be accomplished this week.  The only years that I could find that beat this date for formation of the 14th named storm were 1936 (Sep 10th) and 2011 (Sep 7th).

08 September 2012

As Leslie and Michael head north, new disturbance brews off Africa

 Leslie remains a strong tropical storm, but appears to be on an upward swing today.  It has finally started moving, and is now roughly 250 miles southeast of Bermuda and heading north at 7kts.

With the increased forward speed, it also finally crept into better radar range from Bermuda.  I have a long radar loop available that will continue to add frames as the storm approaches and passes about 160 miles east of the island midday on Sunday (click here). The outer rainbands are already in range, and the developing eyewall should be in range shortly.

After passing by Bermuda tomorrow, it has a 3-day journey to get up to Newfoundland for its next close encounter, then could potentially interact with Michael prior to becoming an extratropical cyclone over the cold northern Atlantic Ocean.  A tropical storm warning is in effect for Bermuda.

Michael has made a bit of a comeback in its satellite presentation today, and remains a 90kt Category 2 hurricane.  Yesterday, the eye filled, the outflow was more asymmetric, and the circulation appeared more elliptical rather than circular, but today it looks a bit healthier... temporarily.

Hurricane Michael is 1100 miles southeast of Newfoundland, and is forecast to gradually weaken as it heads N-NW toward Newfoundland over the next few days.  Again, it will be interesting to see if any sort of binary vortex interaction (Fujiwhara effect) takes place with Leslie and Michael, but it would be on Tuesday-Wednesday, so we have time to keep an eye on that. 

And finally, to the disturbance off the coast of Africa that I mentioned the past couple of days.  The wave has an embedded 1008mb Low centered over the southern Cape Verde islands.  Models continue to be very bullish on this system, bringing it up to a hurricane in 4-5 days.  That may be a little too aggressive, but at any rate, models also agree on it recurving by the time it reaches 50-55W... far from affecting land.  The biggest factor working against it now is the dry Saharan Air Layer to its north, which you can see on this image as the milky air streaming off the continent (you're actually seeing tons of suspended fine dust acting as tracers in the dry air).  The next name on the list is Nadine.

07 September 2012

Special edition on the Saffir-Simpson Scale

I had the opportunity to weigh in on the usefulness and limitations of the well-known Saffir-Simpson Hurricane Wind Speed Scale, and thought I'd share the article with you.  Enjoy!

Leslie making waves along US east coast, Michael weakening

First, a quick mention of the "ghost of Isaac" that was brewing in the northern Gulf of Mexico.  Its window of opportunity to develop has closed... before it took advantage of it.  Conditions are now too unfavorable for genesis, and all that remains is a low-level swirl completely dislocated from what little thunderstorm activity there is.

On to Leslie... a tropical storm watch has been issued for Bermuda, but Hurricane Leslie is in no hurry to get there.  It has remained essentially stationary for the past four days, and MAYBE by Sunday it will start the long-awaited northward trek toward Bermuda and then Newfoundland.  It is a very sloppy 65kt storm now, and after sitting in the same place for so long, has likely upwelled a decent amount of cool water from the ocean depths. 

A long radar loop from Bermuda will help keep tabs on exactly where the center is, and provide constant surveillance of the inner core structure.  Although the center of the storm is currently 1100 miles east of the Florida peninsula, large swells and waves will affect the US east coast from North Carolina up to Maine in the coming days.  Shown here is the wave height forecast valid on Tuesday (wave heights are in meters... multiply by 3.3 to get approximate conversion to feet).  Definitely a concern for boating interests, and for rip currents on the beaches.

Michael has weakened just slightly to a 90kt Category 2 hurricane as of 09Z this morning.  It is forecast to continue the gradual weakening as it heads north into the cold north-central Atlantic.  It's presently located about 900 miles WSW of the Azores and drifting north at 3kts.

Finally, a strong easterly wave left the African coast yesterday, and has an embedded 1007-1008mb Low.  This disturbance is favored by all of the global models to develop rather quickly in the coming days as it heads WNW -- and will likely become Nadine next week.

04 September 2012

Watching tropical storms Leslie and Michael

Over the long weekend, Kirk made the anticipated recurvature at 51W, and then headed northeast into the cold north-central Atlantic hurricane graveyard.  The final advisory was written on Sunday morning as the storm became an extratropical cyclone.

Now on to Leslie and Michael...

Leslie is still a tropical storm, having encountered much stronger vertical shear than expected.  This morning, the storm is remains lopsided, and conditions are not expected to improve until closer to the weekend when it's forecast to become a hurricane.  The forecast track is far away from land... it's currently about 870 miles east of the northern Bahamas and 420 miles north of the Virgin Islands, and crawling northward.

Elsewhere, Tropical Depression 13 formed from an upper-level Low on Monday evening in nearly the place that Kirk formed.  Although it is also rather lopsided and extremely tiny, there are several ships as well as satellite data to support the recent upgrade to Tropical Storm Michael.  Getting the 13th named storm on September 4 is absolutely remarkable.  It's ahead of 1933 and 2004, and just 2 days behind the unprecedented 2005 season (when we needed to borrow six names from the Greek alphabet).  Michael is located about 1400 miles ESE of Bermuda, and about 1300 miles SW of the Azores... truly in the middle of the ocean.  The guidance suggests that it will slowly meander northward and remain a disorganized tropical storm for the next few days  -- no threat to land.