24 November 2008

Disturbance brewing off Panama coast...

With less than a week remaining in the official Atlantic hurricane season, an area of persistent convection has been festering in the extreme southern Caribbean Sea, just off the northern Panama coast.  It's been there for well over a week now, stationary, yet growing in size and ever so slowly getting better organized.

An active microwave scatterometer, a satellite-based instrument which indirectly measures surface wind speed and direction over water, detected reliable winds in the disturbance up to 35kts this morning, but more commonly in the 20-25kt range.  There is moderate southwesterly vertical shear over the system, and SSTs are around 29C.  There is a 1007mb surface Low embedded in the disturbance.  The forecast is extremely difficult, as is usually the case with minimal steering flow.  Some models keep it basically stationary for the next few days, while others give it a slow nudge off to the north or northeast.  If it remains over water, it certainly has the potential to continue organizing.  However, given the motion (or lack thereof), there is time to monitor it.  The biggest immediate threat is flooding rains in Panama, Costa Rica, and Nicaragua.  In the off-chance this gets named, the next name on the list is Rene.

The season has been an active one, with 16 named storms and 8 hurricanes, 5 of which became major hurricanes (CAT3+).  Although there were no CAT5 storms this year, there was a major hurricane in every month from July through November, which was a first.  In July, Bertha reached 105kts, Gustav reached 130kts in August, Ike reached 125kts in September, Omar reached 110kts in October, and Paloma reached 125kts in November.
If one considers an "average" season based on 1950-2000 climatological values of the number of named storms, hurricanes, and intense hurricanes, as well as the longevities of each, and defines that to be 100% of normal activity, this season was 165% of average activity.  It was similar in total activity to 1998's season.

Please visit my tropical Atlantic headquarters.

08 November 2008

Paloma becomes season's 5th major hurricane...

At 03Z last night, Paloma was upgraded to a Category 3 hurricane, making it the 5th major hurricane of the season.  What makes this feat remarkable (unprecedented in fact), is that all 5 major hurricanes occurred in 5 separate months!  Bertha was in July, Gustav in August, Ike in September, Omar in October, and now Paloma in November.  Paloma is also now tied for the 2nd strongest November hurricane on record (Michelle has first at 135kts, and Lenny is tied for second at 120kts).

At 15Z today, Paloma's intensity was 120kts and 943mb, making it a CAT4 storm now.  A long radar loop from Camaguey, Cuba can be found at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/paloma08/Paloma_07-09Nov08_cmw.gif

Shortly after making landfall on Cuba, the storm is forecast to rapidly fall apart, due to a combined effect of land and drastically increasing vertical shear.  However, unfortunate for Cuba is that it should make landfall as a major hurricane, delivering very powerful winds, flooding rains, and a 20' storm surge.

Please visit my tropical Atlantic headquarters.

07 November 2008

Paloma becomes season's 8th hurricane...

As expected, the storm continued to strengthen, and late last night was upgraded to Hurricane Paloma.  As of 15Z today, the intensity is 75kts with a minimum central pressure of 979mb.  It is crawling north at 6kts toward central Cuba.  The satellite presentation is becoming very impressive and it could become the season's 5th major hurricane.

The last major hurricane in November was Michelle 2001 (reached 120kts on Nov 4th as it neared central Cuba... VERY similar to Paloma). The last storm that FORMED in November and became a major hurricane was Lenny 1999, which reached a peak intensity of 135kts on November 17th.  So November is no stranger to very intense hurricanes!

Paloma is forecast to intensify to a CAT3 hurricane before it hits central Cuba this weekend.  A major consideration however, is increasing vertical shear in about a day... so if it will reach CAT3 intensity, it needs to do so quickly. There will (hopefully) be a coherent radar loop from Camaguey at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/paloma08/Paloma_06Nov08_cmw.gif but so far, there have been substantial server glitches preventing reliable data transfers.  The Cuban meteorological service is looking into it though.

Please visit my tropical Atlantic headquarters.

06 November 2008

Paloma finally forms in southwest Caribbean...

After 1.5 weeks of festering convection off the Nicaraguan coast, TD17 formed on Wednesday, and has quickly gotten better organized.  It was upgraded to TS Paloma, the 16th named storm of the season, early Thursday.  As of 15Z, Paloma's intensity was 40kts and 998mb, but is rapidly intensifying, and could be nearly a hurricane by the next advisory.  It has persistent deep convection organized into an eyewall, and the eye is clearing out as I type this.  It's located just off the corner of Honduras and Nicaragua, and crawling north toward western Cuba.  However, it is expected to gradually turn more NE and cross central Cuba late this weekend as a powerful hurricane.  This has unfortunately been a devastating year for Cuba... Fay, Gustav, Ike, and now Paloma.

You will find an updating radar loop of Paloma from Camaguey, Cuba at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/paloma08/Paloma_06Nov08_cmw.gif

An aircraft is en route to more accurately determine the intensity, but it seems to be on a quick path to becoming the season's 8th hurricane.  The ocean under the storm is deep and warm, and the vertical wind shear is minimal.  This is a climatologically favored time of year for these western Caribbean storms that head northeast and cross over Cuba.

Please visit my tropical Atlantic headquarters.

16 October 2008

Omar becomes a major hurricane, TD16 dissipates.

At 03Z today (11pm EDT Wednesday), Omar was upgraded to a major hurricane, the 4th of the season.  Aircraft reconnaissance measured 700 mb flight-level winds of 117 knots and SFMR winds of 108 knots while penetrating the southeast eyewall just prior to the 3Z advisory.  Omar continued to intensify early this morning, briefly reaching Category 4 status according to the 9Z discussion before weakening a bit later this morning.  As of the 12Z update, Omar is listed as an 100-knot (Category 3) tropical cyclone with an estimated minimum sea level pressure of 967 mb.  You can follow Omar's trek through the northern Leeward Islands from Puerto Rico's long-range radar: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/omar08/Omar_15-16Oct08_long.gif.  It is too early to know the extent of damage in the Caribbean, but the system likely caused substantial damage to several island groups including the Netherlands Antilles and French West Indies.
Omar is currently moving rapidly northeastward, being steered by a pronounced digging mid-latitude trough.  The latest motion estimate has it heading NE at 22 kts, up substantially from the estimated 6 kts of motion at the 9Z advisory yesterday.  Omar is predicted to gradually weaken as it moves northeastward over cooler waters, and it likely will begin to undergo extra-tropical transition by the end of the weekend.  Omar is the first major hurricane to form in the month of October since Hurricane Wilma in 2005.
TD16, although in a favorable synoptic environment, was never able to organize and develop.  This was largely due to its proximity to land.  The system has tracked west-southwestward since yesterday and made landfall in northern Honduras yesterday afternoon.  Flooding is the primary concern with the remnants of TD16.  Some of the global models hint at re-development of TD16 as a tropical storm in the eastern Pacific as it continues to drift westward.

Please visit my tropical Atlantic headquarters.

15 October 2008

Omar now a hurricane, TD16 scraping the coast...

At 03Z today (11pm EDT Tuesday), Omar was upgraded to a hurricane, the 7th of the season.  It's presently a 75kt storm with a minimum pressure of 982mb, and still intensifying gradually.  You can spot the eyewall now from San Juan's long-range radar: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/omar08/Omar_15-16Oct08_long.gif

The motion has finally picked up, as predicted, and it's heading NE at 8kts, and it's expected to maintain that motion for the next 3 days.  Within the next day however, it will have its only encounter with land: Puerto Rico and the Virgin Islands.  The latest official forecast track takes it directly over the Virgin Islands early Thursday morning as a strong CAT1 hurricane, possibly CAT2.  But intensity forecasts are tough, especially when considering rapid intensification.  Yesterday evening, the central pressure fell 22mb in 12 hours, but that rate has slowed down since then.  It appears that moderate vertical shear is putting a brake on Omar's previous rapid intensification.  A hefty trough is digging down into the subtropics and tropics, and imposing shear over the system, as well as the northeast motion which will eventually take Omar out into the Atlantic's tropical cyclone graveyard.

TD16, which was located right at the "corner" of Nicaragua and Honduras yesterday, has drifted west and is now just miles off the eastern Honduras coast.  Its proximity to land is preventing it from organizing or intensifying.  As of 15Z, the intensity was 25kts and 1005mb, and heading W at 4kts.  The biggest threat with this system will be flooding and mudslides in Honduras, Belize, and Guatemala.

Please visit my tropical Atlantic headquarters.

14 October 2008

Nana dissipates, TD15 upgraded to Omar, and TD16 forms...

In the face of oppressive 35kt vertical shear, Nana has been written off... only a low-level swirl remains near 18N 44W.

On the other hand, what became TD15 yesterday has been upgraded to TS Omar, and the latest intensity estimate is 35kts and 1001mb.  It's basically stationary (still sitting between Dominican Republic and Aruba), and getting better organized by the hour.  Outflow is healthy, and a large area of cloud tops over the center are persistently -80C and colder.  This could become the season's 7th hurricane within a day or so -- it has the visual appearance of a storm that's on the verge of rapid intensification.  The stagnant motion won't be a big problem as far as the ocean is concerned... the heat content is extremely high in the Caribbean, so there's not really any cool water to be upwelled!  The forecast calls for the motion to pick up in a day, and begin heading NE toward a weakness in the subtropical ridge.  In 1-2 days, this will threaten Puerto Rico and the Virgin Islands.

In addition, the area of disturbed weather off the Nicaraguan coast that I mentioned in yesterday's update was upgraded to TD16, and appears to be on its way to becoming TS Paloma within a day.  It too is over very water water with exceptional heat content, but a limiting factor in its intensification COULD be the proximity to land.  The official forecast takes it from its current position near the "corner" of Nicaragua/Honduras and tracks it west along the coast of Honduras into Belize in three days.  If it does manage to keep a bit further offshore and intensify notably, this could be really bad news for Honduras, which suffered greatly from a stalled major hurricane 10 years ago... Mitch.

Please visit my tropical Atlantic headquarters.

13 October 2008

Nana and TD15 form...

By the weekend, a large area of disturbed weather (hefty easterly wave) in the central Atlantic had already separated into two distinct areas.  The separation occurred in the middle of last week, and this from the same wave I first mentioned on October 1 when it was over Guinea.  On Sunday afternoon, the western portion has been upgraded to TS Nana, the 14th named storm of the season.  It never looked all that organized, but various satellite tools supported upgrading it.  It has since been downgraded to a Depression, and the latest intensity is 30kts and 1007mb.  It's located near 17N 40W and crawling WNW at 6kts.

As of 15Z today, a new Tropical Depression formed in the eastern Caribbean Sea, between the Dominican Republic and Aruba. Intensity is 30kts and 1005mb, and is expected to strengthen as it heads generally NE over the next 5+ days.  In the short term however, steering is virtually non-existent, so it should remain stationary or drift erratically until it gets picked up by an approaching trough in a couple days.  It should pass over Puerto Rico on Wednesday evening, perhaps as a hurricane.  If this seems like a strange track, it is!  Typically, we think of a storm like this heading toward the Yucatan Peninsula or Cuba, but this late in the season, mid-latitude troughs can dig pretty far south and influence tropical cyclone tracks even at 15N.  The next name on the list is Omar.
You can follow the storm on radar when it's close enough...
From Curacao: http://www.weather.an/sat_img/radar.asp#
or from Puerto Rico: http://radar.weather.gov/radar.php?rid=JUA&product=N0Z&overlay=11101111&loop=yes

Elsewhere, there's an interesting area of disturbed weather just east of Nicaragua.  A large area of cloud tops to -70C (and some to -80C) are just 2-3 degrees offshore and the whole area is moving north.  There's an embedded 1006mb Low.  This will also be watched very closely... and should it also get named eventually, the name after Omar is Paloma.

Please visit my tropical Atlantic headquarters.

07 October 2008

Marco comes and goes...

Yesterday morning, TD13 formed in the far south portion of the Bay of Campeche.  It was a small disturbance, but fairly potent for its size.  By 21Z yesterday, it was upgraded to TS Marco, the 13th named storm of the season, based on aircraft recon into the storm.  It intensified to 55kts and made landfall earlier today just north of Veracruz, Mexico.  Marco is now a tiny cluster of weakening thunderstorms over Mexico, barely recognizable as a tropical storm.

Please visit my tropical Atlantic headquarters.

01 October 2008

Laura dissipates...

Convection has dissipated in TS Laura, and the circulation is now over 13C SSTs.  The estimated intensity at the final advisory is 40kts and 995mb.  While 13C is cold, what matters more to a storm is the difference between the "input" air temperature near the surface and the "exhaust" air temperature aloft.  In higher latitudes, the SSTs drop off, but so do the tropopause temperatures (the tropopause is the top of the layer of the atmosphere in which all of our weather occurs).  If the tropopause temperature gets colder faster than the SSTs, the storm "thinks" it's in a good environment!  That's the primary reason we just had a fully tropical system over such cold water.

The circulation is now located just east of Newfoundland and heading north.  It will start recurving to the east with the next mid-latitude trough in a day or two and become a potent extratropical storm affecting the UK this weekend.

Elsewhere, there's a strong easterly wave trekking across Guinea in western Africa.  It is traceable back about 5 days over the Ethiopian Highlands.  A majority of forecast models develop this system once it exits the coast in about 3-4 days.  And finally, there's an easterly wave centered near 14N 40W which is currently poorly organized but could slowly develop.

Please visit my tropical Atlantic headquarters.

29 September 2008

Kyle comes and goes, Laura forms...

Since my last update on Thursday, the disturbance that was near Hispaniola was upgraded to TS Kyle, then Hurricane Kyle, and  recently transitioned to an extratropical cyclone.  It was around as a named storm for just 3.5 days, and as a hurricane for 1.25 days.  It ended up following the forecast tracks very well, traveling straight north into Nova Scotia as a potent tropical storm.

And as of this morning at 09Z, Sub-Tropical Storm Laura formed in the north central Atlantic and won't be threatening anything but shipping lanes.  It's located near 38N 47W and tracking WNW at 7kts, but that will become N very shortly.  Intensity is 50kts and 995mb.  SSTs are 25-26C, and will be dropping to 20C, then 15C within a couple days.  However, it could still become a minimal hurricane in this time (or "sub-tropical hurricane") if the upper-level temperatures cool off with the SSTs and shear remains low enough, which it should.

Please visit my tropical Atlantic headquarters.

25 September 2008

Still two unnamed storms to threaten US east coast...

Very little has changed since yesterday's update, so this will be very brief.  The disturbance north of Hispaniola is still there, and is gradually getting better organized... intensity is now estimated at 1003mb and 30kts.  And the one off the NC/SC coast is also still there, moving very slowly but heading for the coast, now has an intensity of 55kts and 998mb.

Strangely, neither of these systems are numbered or named yet, nor are there even "special tropical disturbance" alerts out for them.  The Florida State University Cyclone Phase Space diagrams are often used to determine the structure of cyclones, whether it be extratropical, subtropical, or tropical, and both of these systems are analyzed as "symmetric warm core" (i.e. tropical) by a majority of models.
http://moe.met.fsu.edu/cyclonephase/ (scroll down to the different models, select a model, then select the cyclone of interest)

If either of these ever get named, the next two names are Kyle and Laura.

Please visit my tropical Atlantic headquarters.

24 September 2008

Two systems may threaten US east coast in coming week...

The area of disturbed weather that was over eastern Hispaniola a couple days ago is just now exiting the northern coast of that island, leaving behind yet another round of devastating flash floods.  And as is typically the case, the island devastated the storm as well.  There's barely any deep convection remaining, and no evidence of a low-level center.  However, now that the mid-level circulation is over warm water, and there's minimal vertical shear, its chances for reorganization are pretty high.  In the coming days, it's expected to head north toward New England and Nova Scotia as a strong tropical/extratropical storm.

Elsewhere, a potent sub-tropical Low has formed immediately off the NC coast along a decaying frontal boundary.  Intensity is 1008mb and 55kts, and is located 250 miles SE of Wilmington.  It's forecast to track generally NW toward the coast, strengthen somewhat, and perhaps gradually acquire more tropical characteristics.  You can monitor it from the Morehead City NC radar at http://radar.weather.gov/radar.php?rid=MHX&product=N0Z&overlay=11101111&loop=yes
Regardless of how it's classified, it is and will continue to be a hazard for coastal NC, producing strong winds, high seas, and eventually, a lot of inland rain.

Please visit my tropical Atlantic headquarters.

22 September 2008

Hispaniola getting another unwanted dose of heavy rain...

An easterly wave that exited the African coast about 2.5 weeks ago (it's been in no rush) is now hovering over the Puerto Rico and Hispaniola area, and is slowly getting better organized.  Last Thursday, it was centered down near Barbados, and since then has turned northward and is presently over the Dominican Republic and has a 1008mb Low associated with it.  It's nearly a Depression, but lacks a well-defined surface circulation.  The cloud tops have been persistently cold, and the outflow is improving, indicating that the vertical shear is decreasing over it.

You can view a radar loop of the disturbance from Punta Cana, Dominican Republic at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/kyle08/Kyle_22Sep08.gif
(new frames will continually be added, so keep checking it!)

It is forecast to continue moving north over the next few days, and gradually intensify.  The US east coast should be aware of this, as it could be affecting the coast by week's end.  The next name on the list is Kyle.

Please visit my tropical Atlantic headquarters.

15 September 2008

Ike finally out of the picture...

For the past two weeks, Ike has been a headline.  But finally, early morning Saturday (local), it made its final landfall as a 95kt hurricane, with a monster storm surge.  And although it was deadly and destructive, in the US as well as other countries, the worst-case scenario was narrowly avoided.  The center of the eye passed directly over downtown Galveston and Galveston Bay, and slightly to the east of downtown Houston.  This placed the largest surge and strongest winds just 10-15 miles east of there.  Amazing to think what those 10-15 miles did to "save" Galveston and Houston... the surge was much less than anticipated, though still substantial.  Despite the destruction that occurred there, anyone would agree they got off very lucky: it could have been MUCH worse.  A mere 10 miles further south, and the death toll would be in the thousands instead of the dozens, and the financial hit would have been the largest in US history.

Flash flooding and downed power lines are an enormous problem from Texas to Canada in Ike's wake.  Nearly 4 million people are without power, and could be for a long time.  Flooding in the midwest was responsible for several of Ike's fatalities.  The following map shows estimated precipitation in the past week, and you can clearly see the swath from Houston to St Louis to Detroit.
(you may need to copy and paste the URL if it's too long)

If anyone has personal accounts from the storm, please feel free to share them, and if you wish, I can share them with the list.

The basin is fairly inactive now, giving Haiti, Cuba, and the US a much-deserved break.

Please visit my tropical Atlantic headquarters.

12 September 2008

Ike heading for Galveston and Houston...

The forecast track for Ike has not budged in the last day, and it still looks like Galveston/Houston are in extreme danger.  Ike has strengthened a little to 90kts, but appears that it's finally completing the dragged-out eyewall replacement cycle, which should allow it to intensify before landfall.  It's getting much better organized, with rejuvenated convection encircling the eye.  Its tropical storm force winds already extend inland from Galveston eastward to the LA/MS border.  Hurricane force winds extend out as much as 120 miles from the center now.  This is a VERY large and powerful storm, carrying with it the potential for a 25' storm surge into Galveston Bay.  This surge could be greater than Camille's, Carla's, and Katrina's, so it should certainly be taken seriously.

Galveston Island is already flooding, and Ike is still 200 miles offshore.  Eastern Houston is also expected to flood later tonight and into Saturday morning.  So far, only 1/2 of Galveston had been evacuated... hopefully the remainder make it out in the next few hours, or we could face a catastrophe not unlike the Galveston Hurricane of 1900.  A pier on the Gulf side of Galveston Island is already reporting water levels 6' higher than normal.  And a buoy just offshore from the northern tip of the island is experiencing 19' significant wave heights (individual waves could be twice that high)... and still increasing.

The latest full-resolution visible satellite loop is at:
and 1-minute imagery from GOES-W is at:

A long-range radar loop from Houston is at:
and the short-range version is at:

You'll find additional reports on the storm at http://topics.blogs.nytimes.com/tag/hurricanes/

Landfall is still expected to occur in the early morning hours on Saturday, but that's when the center of the eye crosses the coast.  Severe weather and flooding is already occurring inland, and will only get worse as the day goes on.  It could come ashore as a CAT3 storm, given its recent trend in appearance.

Elsewhere, an easterly wave that had been strongly sheared is entering a more favorable environment and is now located just east of the Bahamas.  This seems to be related to the remnants of Josephine... it will be monitored for development as it heads toward the southeast US coast.  This could be another potential TS/CAT1 landfall as early as Monday.  The next name on the list is Kyle (unless it's determined that it has enough Josephine ancestry, then it would be brought back as Josephine).

Please visit my tropical Atlantic headquarters.

11 September 2008

Ike now a serious threat to the entire Gulf coast...

As of 15Z today, Ike was still an 85kt CAT2 hurricane (945mb), but the feature that is becoming very disconcerting is the SIZE of the storm (defined as the radius of the wind field).  Tropical storm force winds should be affecting nearly all of LA and TX coasts within a couple days.  Right now, hurricane force winds extend out 100 miles to the north and east of the center.  A hurricane warning is already in effect for much of the TX and LA coasts, and Galveston and Houston have begun evacuating.  Landfall is expected just south of Houston in the early morning hours on Saturday as a CAT3 hurricane.  There is a substantial risk for storm surge flooding now through Saturday from Brownsville to Mobile, with the highest risk centered on Galveston Bay.  Ike is already more powerful than Katrina or Rita, as measured by its kinetic energy and potential for storm surge.

Storm surge is influenced by five primary factors: storm size, storm translation speed, storm direction, storm intensity, and bathymetry.  All five are working against the western and northern Gulf coast now, most notably the northern Texas coast, which is at extreme risk.
Ike is a strong storm, and still gradually getting stronger... it's also a large storm, and gradually getting larger.  It is moving slowly, and in a straight line (no curves in the track), and the Gulf coast has an extensive continental shelf offshore.  These all combine to produce an enormous storm surge over a large stretch of coastline.

The Navy has a model that predicts significant wave heights (individual waves could be twice as high as the sig wave ht):

The NHC produces a graphic showing the probability of a 5' or greater storm surge:

The maximum potential surge height is shown at:

And NHC runs a sophisticated storm surge model called SLOSH which accounts for storm motion, bathymetry, topography, etc... a worst-case scenario for a CAT3 Galveston Bay landfall can be found here:

Please visit my tropical Atlantic headquarters.

10 September 2008

Ike strengthening as it heads for Texas...

Over the past 18 hours, Ike has strengthened by 15kts and 11mb, and much more is likely in the coming days.  As of 15Z, it's at 80kts and 957mb, and it appears that an eyewall replacement cycle is beginning.  This should put a halt on any rapid intensification, but opens the gate for substantial intensification once the cycle is complete.  The motion is WNW at 7kts, and this expected to continue, only gradually speeding up somewhat over the next few days.

You can view a great full-resolution visible image loop at:

The latest official forecast shows a landfall near Corpus Christi very early Saturday morning as a CAT3-4 hurricane.  In the meantime, SSTs will be in the 29-30C range, and weak to moderate vertical shear.

Some parts of the Texas coast have already begun evacuations, particularly the Galveston and Corpus areas.  So far, Ike is responsible for about 75 deaths in Haiti and Cuba.

Please visit my tropical Atlantic headquarters.

09 September 2008

Ike heading into Gulf...

Ike is now just an hour or two away from exiting western Cuba and entering the Gulf of Mexico.  It has just tracked over the same swath that Gustav did as a CAT4 hurricane... a very devastating situation for Cuba.  As of 15Z, Ike's intensity was 70kts and 965mb... tracking WNW at 11kts.

The radar loop from Casablanca, Cuba can be found at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/ike08/Ike_08-09Sep08_csb.gif

The forecast track has continually been shifting westward, and is now centered on Corpus Cristi, TX midday Saturday as a major hurricane.  Under the forecast track, the oceanic heat content is maximized, allowing Ike the most time over the deepest and warmest water.  Vertical shear is also expected to remain very low.  Intensity should start increasing within hours of exiting Cuba, and the storm is already looking impressive on satellite imagery.  It could certainly regain CAT4 status by the central to western Gulf.

Please visit my tropical Atlantic headquarters.

08 September 2008

Ike makes landfall on Cuba...

At about midnight local time, Ike make landfall on Cabo Lucrecia as a Category 3 hurricane.  It has since tracked westward across the island, and has recently exited just north of Gulfo de Guacanayabo as a minimal Category 2 hurricane.  Over the coming day, it will pass along the southern length of the island, then cross back over Cuba where Gustav did as a Category 4 storm less than 2 weeks ago.  Then it'll have about 4 days in the Gulf of Mexico prior to a US landfall.

As of 15Z, Ike is an 85kt hurricane, with a central pressure of 960mb.  It's heading W at 12kts.  The storm has lost the majority its deep convection, and the inner core has been disrupted.  It should be able to reorganize quickly over the very high oceanic heat content on the south side of Cuba.  The latest forecast track indicates a Houston landfall this weekend as a major hurricane.  However, 5-day forecasts have an average error of 220 miles, so don't focus too much on the exact forecast track.

Once exiting Cuba, the Gulf will be the factor in how much Ike will reintensify.  Ike will cross over the Loop Current, a deep warm patch of water in the east-central Gulf.  After that, the northern Gulf shelf waters are warm, but not very deep.  In the following two plots, you'll find the sea surface temperature (a "skin" temperature), and the oceanic heat content (an integrated energy content from the surface down to the depth of the 26C isotherm).  As you'll see, the surface can be warm, but if that warmth doesn't run deep, a strong hurricane can stir up cool waters quite easily and weaken.  The exception would be storms that are moving fairly quickly... they may stir up cooler water, but they're already past that patch of cooled ocean by the time it would have an influence.

Taking these and other factors into consideration, here is a plot of the MPI, or Maximum Potential Intensity, which I described in Sept 4th's update.

Please visit my tropical Atlantic headquarters.

06 September 2008

Hanna makes landfall, Ike heading for Cuba, Josephine dissipates...

At about 3am EDT, Hanna made landfall on the SC/NC border as a 60kt (983mb) tropical storm, just under hurricane intensity.
As of 20Z, the center is located near the DelMarVa peninsula and tracking NNE at 21kts.  The radar loop covering landfall can be found at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/hanna08/Hanna_06Sep08.gif

It will now continue N-NE over the east coast, from VA to ME, over the next 24-36 hours, then out to the cold north Atlantic as a potent extratropical cyclone.  Tropical Storm warnings still are in effect from northern NC up through NH.

Attention now shifts to Ike, which as of 15Z, was a 95kt hurricane with a central pressure of 960mb.  It is forecast to intensify as it heads WSW then W, but periodically weaken as well as it passes over Cuba in a couple of days.  Once leaving Cuba, it should head WNW-NW into the central Gulf and up toward the north central Gulf coast.  The northern Gulf coast should be watching this very closely, and be prepared for a significant landfall as early as Friday.

It is located just north of Hispaniola, giving more rain to the already flooded countries of Dominican Republic and Haiti.  Then it will pass over the eastern Bahamas, where Hanna sat for a few days.  You can find the latest infrared satellite image of Ike at http://rammb.cira.colostate.edu/ramsdis/online/latest_image_640.asp?product=tropical_ge_4km_ir4_floater_2

You will find a radar loop from Camaguey, Cuba at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/ike08/Ike_07-08Sep08_cmw.gif

As the time nears, there will also be radar loops available from Casablanca, Cuba, and Key West, FL (Mon-Wed timeframe).  Hurricane Warnings cover the eastern Bahamas, while Hurricane Watches cover the central Bahamas and eastern Cuba.

At 09Z, advisories ceased for Josephine, as vertical shear took its toll on the system.  Regeneration, if at all, would be at least a week away, but very unlikely.

Please visit my tropical Atlantic headquarters.

05 September 2008

Hanna nearing landfall...

Just in time for landfall, Hanna is getting organized, and has very strong centralized convection now.  The center is located about 140 miles southeast of Charleston as of 7pm EDT (23Z) and tracking north at 17kts.  At this rate, it should be making landfall somewhere between Myrtle Beach SC and Wilmington NC in about 6 hours (1am local time).

Given the current satellite and radar presentation, it could become a hurricane prior to landfall.

Radar loop from Wilmington:

Infrared satellite loop:

Another important consideration is that the storm has a large wind field, so being right under the center doesn't matter so much.  Tropical Storm Warnings and Watches cover the eastern coast from Georgia up to New Hampshire now.... while Hurricane Watches cover SC and NC.

Please visit my tropical Atlantic headquarters.

Hanna less than a day from US landfall, Ike looming ominously north of Lesser Antilles, Josephine still battling shear...

Hanna is a 55kt tropical storm, finally able to get better organized now that the vertical shear has decreased to less than 20kts.  It is now east of Daytona Beach FL, but heading NW-N toward the Charleston SC area.  Landfall is expected there early Saturday morning as a tropical storm.  Watches and warnings for the coasts can be found at http://www.nhc.noaa.gov/storm_graphics/AT08/refresh/AL0808R+gif/
It's possible that Hanna could become a minimal hurricane just prior to landfall, given the recent trend in organization.
In the coming days, tropical storm force winds, along with the potential for flash flooding and tornadoes, extend up into new Jersey, New York, and even New England, as Hanna transitions to a potent extratropical storm.

Now on to Ike.  Ike is shaping up to be a serious threat to the Bahamas and the US this weekend into the middle of next week.
Vertical shear is presently moderate, but will be decreasing, and SSTs will be 29-30C in the coming week.  As of 15Z, intensity is 105kts and 954mb, and tracking W at 14kts.  It is entering the expected timeframe of strong vertical shear, and it shows!  The storm is quite lopsided now, with nearly all convection and outflow on the south half.  Ike could weaken to a CAT2 storm before the shear lets up in a couple days.  It's then forecast to regain CAT3 or CAT4 status as it passes directly over Hanna-battered Bahamas, then onto extreme southern Florida by late Tuesday.

Josephine is now nothing more than an exposed low-level swirl.  It is still classified as a 40kt tropical storm, but is barely even that.  In the next few days, shear is forecast to remain strong over the system, but in 4-5 days, could decrease a bit and start allowing Josephine to make a comeback.  Again, it is near no land and no islands, even looking out one week.

As a side note, as of today, we are at the amount of activity in an "average" season, and this one's not even half way over yet.  The activity is defined by the Net Tropical Cyclone index, or NTC, which combines the numbers of storms, their intensities, and their longevities, and compares it to a climatological average of each quantity.

Please visit my tropical Atlantic headquarters.

04 September 2008

Hanna heading northwest, Ike rapidly intensifies, Josephine getting sheared...

Hanna is succumbing to strong vertical shear and very dry ambient air, and is now not much more than a broad exposed low-level circulation.  It still has some convection associated with it, but it's weak and far removed from the center.  It's still being classified as a 55kt tropical storm, and forecast to reach minimal hurricane status before landfall on Saturday morning near the central NC coast (despite no model guidance supporting that intensity).  It is now located just north of the central Bahamas and tracking NW.

When I wrote my update yesterday, Ike was a 60kt tropical storm with a central pressure of 991mb.  Six hours later, it was at 70kts and 984mb.  Another six hours: 115kts and 948mb.  And yet another six hours: 125kts and 935mb.  So, the pressure fell 36mb in 6 hours, 49mb in 12 hours, and 61mb in 24 hours.  Ike very easily met the criteria for rapid intensification, and also was within 5-10kts of its Maximum Potential Intensity (MPI).  MPI is a theoretical upper bound for a storm's intensity given its location, oceanic and atmospheric environments, etc.  Few storms reach their MPI, and some even exceed it (because MPI is not a flawless quantity).

Here are infrared and microwave satellite images from 0745Z and 1136Z today, with Ike as a 125kt hurricane:

So, Ike reached a peak intensity (so far) at 09Z today, at 125kts and 935mb.  As of the 15Z advisory, it's 120kts and 938mb, still a powerful Category 4 storm.  It is starting to encounter some moderate northerly vertical wind shear, and should continue to gradually weaken over the coming 2-3 days (still a strong hurricane though), then after 3 days, the shear is expected to let up a bit, allowing Ike to reintensify as it heads into the Bahamas early next week.  It's presently located near 23N 58W and moving WNW at 14kts.

Josephine is in a hostile environment and barely holding steady as a 45kt tropical storm.  Like Hanna, its satellite presentation is poor, at best.  It will be in strong shear for the next 4 or so days, then perhaps have a shot at regeneration.  In the meantime, it will track WNW over open ocean... not a threat to any land or island for at least a week.

Please visit my tropical Atlantic headquarters.

03 September 2008

Hanna still stalled, Ike nearly a hurricane, Josephine getting organized...

Hanna is still over the eastern Bahamas, dumping rain over those islands, as well as Haiti and the Dominican Republic, both south of the storm's center.  Hanna is responsible for at least 23 deaths already, all due to flooding.  At the time of this writing, the center of poorly-organized TS Hanna is located just east of Great Inagua, Bahamas, and heading north at 5kts.  Intensity is 50kts and 997mb, and forecast to gradually strengthen to a minimal CAT1 hurricane over the next three days.  US landfall is expected early on Saturday near Myrtle Beach... or more correctly, somewhere in the GA/SC/NC vicinity.

Ike is now a 60kt tropical storm (just shy of hurricane intensity) near 21N 52W... several days away from anything.  While that sounds like a good thing, it gives the storm 4-5 days to intensify.  The official forecast brings Ike to a CAT3 hurricane over the Bahamas in five days.  The current satellite presentation is impressive... with symmetric outflow aloft, intense convection gathered over the center, and an eye opening in VIS and IR imagery.  Florida may want to keep a real close eye on this one for next Tuesday-Wednesday...

Finally, Josephine is still a TS as well, and now located near 14N 29W.  Intensity is 55kts, but vertical shear is beginning to increase, and it has a day or so to intensify until the shear becomes oppresive.  It is very far from any land, even looking out a full week.

I posted a brief summary of the "why?" behind the current flurry of activity at http://topics.blogs.nytimes.com/tag/hurricanes/ (Sep2, 7:45pm entry).

Please visit my tropical Atlantic headquarters.

02 September 2008

Gustav, Hanna, Ike, and Josephine: the Atlantic is alive...

Since making landfall on LA yesterday morning, Gustav has drifted inland and is now centered near Shreveport LA, dumping copious amounts of rain over LA, eastern TX, AR, and MS.  It is now a 30kt tropical depression, and will continue to spin down.  Gustav was a very powerful and deadly hurricane, certainly not to be forgotten.  It caused tens of billions of dollars in damage and perhaps a hundred deaths across Haiti, Cuba, Jamaica, and the US.

Leaving no time to recollect a sense of normalcy, Hanna is over the Bahamas, Ike is in the central Atlantic, and Jospehine is near the Cape Verdes.

At the 15Z advisory today, Hanna was still stalled over the eastern Bahamas, and was downgraded to a 60kt (987mb) Tropical Storm.  Vertical shear is taking a toll on the system, and it could be a couple days yet until it relaxes.  Hanna is forecast to regain hurricane intensity on Thursday as it heads NW toward the southeast US coast.  Landfall is expected on Friday, perhaps clipping the Daytona Beach area, then up to the Charleston area.  Again, remember even 3 day forecasts can be off an average of 140 miles.  A hurricane warning is in effect for the eastern Bahamas, as far west as Cat Island and Great Exuma, and all the way east to the Turk Islands.

Since my second update on Labor Day, TD9 was upgraded to TS Ike, and is now a 50kt Tropical Storm with a central pressure of 1002mb.  Ike is located near 19N 45W and moving W at 16kts, and is poised to become the next hurricane in a couple of days (and perhaps a major hurricane after that).  In 5 days, NHC places Ike almost exactly where Hanna is now... down to the mile almost (always keep in mind the expanding envelope of forecast track errors with time though)!  So the Bahamas and Cuba should be preparing for this, and after that, the US in a week or so.

Also since my updates yesterday, the potent easterly wave I mentioned that had just exited Africa was upgraded to TD10, then quickly to TS Josephine, the 10th named storm of the season.  It's now near 13N 25W and tracking W at 13kts.  Intensity is estimated at 35kts, and 1005mb (and probably increasing rapidly).  This could become a hurricane within a day, but is at least a week away from any land or island.  The satellite presentation is very impressive now, with what appears to be an eye already forming.

Please visit my tropical Atlantic headquarters.

01 September 2008

Hanna now a hurricane...

Minutes after sending my update out today, Hanna was upgraded to a hurricane, the 4th of the season.  Intensity is now 65kts and 985mb, and it's more or less stalled over the eastern Bahamas.

Please visit my tropical Atlantic headquarters.

Gustav makes landfall, Hanna and TD9 heading for US coast?...

Another powerful Labor Day hurricane for the record books.  A little sooner than expected, Hurricane Gustav made landfall near Cocodrie LA at about 15Z today, at an intensity of 95kts and 955mb.  You can watch the landfall via the New Orleans radar at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/gustav08/Gustav_01Sep08_LIX.gif

A buoy located roughly 60 miles south of Pascagoula MS reported 34' significant wave heights** (individual waves could have been much higher).  The water there is about 900 feet deep, and the SST was 30.7C yesterday before the storm got there, now it's 27.9C.
Other notable automated observations come from Grand Isle:
and New Canal:

It's too early to know the extent of the damage in southern LA, as the storm is still there.  Levees in New Orleans have already been overtopped, but as of this writing, are still intact.  The next day or so will be the real test as time and pressure wear on... fortunately, the majority of the city is evacuated.  It will now continue to track inland over LA and eastern TX, likely spawning tornadoes and causing major flooding.  Four tornadoes have been reported so far in MS and FL, and flood warnings cover much of LA, MS, FL panhandle, eastern TX, and southern AR.  Without a doubt though, the name Gustav will be retired after this season, with probably ~100 deaths attributed to the storm, and tens of billions of dollars in damage across 4 countries.

TS Hanna is presently crawling (4kts) over the eastern Bahamas, creating flooding problems there.  Latest intensity is 50kts and 994mb.  It will pick up forward speed in a couple days, and then likely intensify to a hurricane as it heads for the southeast US coast on Friday.  Right now, the official forecast places landfall at the GA/SC border, but keep in mind that track errors 4 days out can be significant.  Recent satellite imagery is impressive: a centralized shield of very clod cloud tops (as cold as -85C), perhaps indicating that the jump to hurricane status is nearing.

At 15Z, the disturbance that was near 16N 35W yesterday was upgraded to TD9, and is now at about 18N 40W and tracking W at 14kts.  Intensity is 30kts and 1005mb, and gradual intensification is expected as it heads west.  This could certainly be TS Ike by this evening, and a hurricane by mid-late-week.  In the long term, this could be of great interest to Florida.

And as if the list wasn't long enough already, there's a new very potent easterly wave that has just exited Africa.  It's located at about 12N 20W, and has a 1007mb Low embedded within the wave.  Assuming TD9 takes the name Ike, the next name on the list is Josephine.

Please visit my tropical Atlantic headquarters.

**Significant wave height is calculated as the average of the highest one-third of all of the wave heights during the 20-minute sampling period.

31 August 2008

Gustav heading for Louisiana, Hanna heading for the Bahamas, TD9 ready to form...

Gustav underwent rapid intensification Friday evening through Saturday afternoon.  In 24 hours ending 00Z Sunday, the central pressure fell 34mb, and in 23mb in 12 hours.  It strengthened from a 60kt tropical storm to a 130kt CAT4 hurricane in 27 hours.  Unfortunately, it accomplished this while heading for, and passing over, western Cuba, causing extensive damage.

Since exiting Cuba, it has had a hard time reorganizing, though still a 100kt CAT3 hurricane.  It is heading NW at 15kts, toward the central LA coast, and landfall is expected Monday morning as a major hurricane near Marsh Island.  However, there is still uncertainty, and a hurricane warning covers the LA and MS coasts.  As far as Katrina-ravaged New Orleans goes, so far about 15,000 people have evacuated, and evacuation orders are still in place for the city.  Lake Pontchartrain can expect a 15-20 foot storm surge on Labor Day, which will certainly re-test the levee system protecting the below-sea-level city.  Other parishes in coastal LA also have mandatory evacuation orders.  As of this writing, over 3/4 of oil production in the Gulf has ceased, as platforms and rigs are evacuated and shut down for the duration of the storm.

The latest intensity is 100kts and 962mb.  It is forecast the strengthen a bit more again, perhaps to CAT4 status, before landfall.  It's currently looking ragged on satellite, lacking a clear eye, showing signs of southerly vertical shear, and has dry air wrapping around west and south of it.  The main factor in its favor is deep, warm water under it.

You will be able to track its progress toward the coast via radar loops that I'm generating... a long and short range from New Orleans, and a short-range from Lake Charles (all are available at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/).

Hanna, still maintaining modest tropical storm intensity, is strongly sheared.  Latest intensity is 45kts and 999mb, and heading WNW at 9kts.  It's now a couple degrees north of the Turk islands, and it is expected to track slowly westward toward the Bahamas, then NW toward the southeast US coast as a hurricane.  Landfall could be sometime next weekend... however, the steering environment is incredibly complicated, and Hanna will just have to be watched for the next few days to figure out where it's going!

The easterly wave I mentioned 2 and 3 days ago near the Cape Verdes has gotten better organized and is now located near 16N 35W.  Development of this wave should be slow as it heads W at 12kts.  The next name on the list is Ike.

Please visit my tropical Atlantic headquarters.

29 August 2008

Gustav exits Jamaica, Hanna gaining strength also...

First of all, today marks the 3-year anniversary of the final, historic, and infamous landfall of Hurricane Katrina.  Katrina was a Category 3 hurricane when it came ashore near the LA/MS border.  It was responsible for 1833 deaths, and $81 billion in damage.  Though not in the running for the deadliest landfall, it did set the record for the costliest landfall, and costliest natural disaster for that matter, in US history.

Another bit of history to point out as we look ahead to the holiday weekend is the infamous Labor Day Hurricane of 1935.  This storm mostly affected the Florida Keys, and was the most intense (by pressure) US landfall on record... Camille was #2, Katrina was #3, and Andrew was #4.  It was responsible for over 400 deaths and it basically obliterated Islamorada and other towns/keys in extreme southwest Florida.  Fortunately, residential air conditioning wasn't affordable or practical yet and Florida was barely populated compared to today (during the 1950's, the state's population grew by 79%, largely because of A/C!).

Now back to 2008.  Gustav has completed its trek over Jamaica, but has already caused at least 59 deaths across Haiti, Dominican Republic, Jamaica, and Cuba.  It is now over open, deep, warm water and poised to intensify to a powerful hurricane as it heads WNW toward western Cuba, then into the Gulf of Mexico.  As of 15Z today, the intensity is 55kts and 988mb and is located 165 miles from Grand Cayman.  It has sped up a little and is now moving WNW at 7kts (has been 3-4kts lately).  All conditions and current appearance suggest rapid intensification is primed to take place.  The latest satellite images indicate that an eyewall is forming already.

So of course, the question is what about landfall?  The western tip of Cuba is the next target probably on Saturday evening as a strong hurricane.  Then the US gulf coast is next, probably Tuesday morning as a very strong and dangerous hurricane.  The current NHC forecast track is centered on the middle LA coast, but anywhere from Corpus Cristi, Houston, New Orleans, Panama City is within the 5-day average track error cone.  Coastal residents within this range should at least begin basic preparations.

Hanna is still a tropical storm as well, and like Gustav, is on an intensification trend.  TS Hanna is moving WNW at 10kts and intensity is estimated at 45kts and 1000mb.  It is forecast to continue strengthening, and slowing as it heads WNW... then by the end of the weekend, start turning SW toward the Bahamas.  A long-range model run, shown here, forecasts Hanna to then turn westward, enter the Gulf, and make landfall on LA late next week as a strong hurricane. This plot is valid Friday evening (Sept 5):  http://www.ecmwf.int/products/forecasts/d/getchart/catalog/products/forecasts/medium/deterministic/msl_uv850_z500!Wind 850 and mslp!192!North America!pop!od!oper!public_plots!2008082900!!chart.gif

Elsewhere, the easterly wave that exited the African coast yesterday is now just east of the Cape Verdes and still looks impressive on satellite.  Central pressure of the Low associated with the wave is estimated at 1007mb.  This will likely be the next named storm in a couple days: Ike.

Please visit my tropical Atlantic headquarters.

28 August 2008

Gustav heading for Jamaica, Hanna forms...

After crawling across Haiti's southwestern peninsula and almost losing tropical storm status (it weakened to 40kts and 999mb yesterday), Gustav is now back over water, but made a remarkable turn in the last 12 hours or so.  Rather than the expected westward track which would have put it along the southern edge of Cuba, it turned southwest and is now east of Jamaica and should end up passing over or SOUTH of Jamaica!  From that point, the previous forecast track remains unchanged: clip the extreme western tip of Cuba (or miss it by a little), then enter the central Gulf, then head NW toward Louisiana.  The official forecast, which agrees with many models, is for a major landfall on Labor Day in/near Louisiana.

As of 15Z, Gustav was located on the eastern tip of Jamaica, with an intensity of 60kts and 983mb... nearly a hurricane again.  It appears to be forming another eye, but the mountains of Jamaica could disrupt that later today.

The HWRF forecast is shown at (surface winds and sea level pressure):
It is forecasting an extremely intense hurricane in the Gulf and at US landfall... reaching it's peak intensity of 894mb and 137kts on Sunday evening.  If this verifies, it could rival the infamous Labor Day Hurricane of 1935.  As usual, do not focus on the exact track... the 3-5 day range has too many uncertainties, but should be used as a guideline for preparedness.  Certainly anyone in coastal LA, MS, AL should at least be preparing for this.

The disturbance that was near 20N 57W yesterday was upgraded to TD8 early this morning, then TS Hanna later this morning.  Latest intensity is 35kts and 1002mb and it's located near 20N 59W.  it is forecast to gradually intensify to hurricane status and head westward toward the US east coast in a week or so.  At its somewhat far north location, it would be easy for it get recurved by a mid-latitude trough though.

And, a new easterly wave has exited Africa (near 18W) and is already quite impressive.  It will be watched for further development.  The next name on the list is Ike.

Please visit my tropical Atlantic headquarters.

27 August 2008

Gustav temporarily weakens over Haiti...

At 03Z last night, Gustav was downgraded to a Tropical Storm, and is still at that status, as it passes over the high mountainous terrain of Haiti's southwestern peninsula.  And it's doing so very slowly (~4kts).  The flash flooding there must be terrible.
An AP report from Haiti states "rising water was threatening crops in Haiti, already a powder keg because of spiking food prices. Earlier this year, there were deadly protests over the high cost of food.  Gustav lingered over the nation's impoverished and deforested southern peninsula, threatening banana and vegetable fields.  Residents in coastal Les Cayes ignored government warnings to seek shelter, instead throwing rocks in protest of Haiti's poor economic conditions".  Not a good situation.  And now Gustav is eyeing up Cuba, Jamaica, and the Cayman Islands.

The western tip of Cuba could have a brush with an intense Gustav on Saturday, then the storm enters the central Gulf of Mexico, where it's forecast to gradually start turning toward the NW.  Presently, Louisiana is a likely target on Monday, but the situation will of course be very carefully watched and forecasts will be tweaked.

The HWRF model (WRF model that's coded to specialize in hurricanes) has the following forecast out to 5 days (the fields shown in the large plot are sea level pressure in the line contours and vorticity in the shaded contours... and in the zoomed plot are sea level pressure in the line contours and surface wind speed in the shaded contours):
LARGE: http://einstein.atmos.colostate.edu/~mcnoldy/tmp/gustav/gustav_absv_p.gif
ZOOMED: http://einstein.atmos.colostate.edu/~mcnoldy/tmp/gustav/gustav_wind_n.gif
HWRF shows a peak intensity of 901mb  and 135kts late this weekend, and a major landfall very similar to that of Camille and Katrina.  The official NHC forecast currently agrees very well with this scenario, but it's still 5-6 days out.

The easterly wave that was near 20N 56W yesterday has barely moved and is now near 20N 57W.  It's estimated at 25kts and 1009mb, and although vertical shear has made development a challenge these past few days, it is forecast to lessen and allow this system to get better organized.  The one near the Cape Verdes is lacking organized convection now, but will still be watched closely.  This is the time of year when a lot can happen at once!

Please visit my tropical Atlantic headquarters.

26 August 2008

Gustav now a hurricane...

Not only is Gustav a hurricane, it's almost a Category 2 hurricane already!  The central pressure has fallen 25mb in 24 hr, and 9mb in 12 hr.  Certainly not extremely rapid intensification (yet), but fast enough to warrant concern.  In microwave imagery and aircraft recon data, there is a small eye/eyewall too, but no open eye is yet apparent in visible or infrared imagery -- that could change in a few hours though.  You can monitor a high-resolution visible satellite loop here:

The latest intensity (15Z) is 80kts and 981mb, with significant intensification expected over the next week.  It should weaken a little bit as it passes over the southwestern peninsula of Haiti, but the ocean is so incredibly warm and deep under Gustav's predicted path (combined with little to no vertical shear), that there's no foreseeable reason that this will not be an extremely powerful hurricane in a few days.

As far as the track goes, things aren't looking good for Cuba or the US.  A major hurricane landfall on the US Gulf coast looks inevitable, but this far out, it's too hard to say where along the coast.
The GFDL model's 06Z run paints an ominous picture for Lousiana and Mississippi:
This is one model and one run, and 5 days out, but a situation worth preparing for nevertheless.

Just for the record, you first heard about what's now Gustav in my August 14 update: "
an impressive easterly wave has just exited the African coast and is just south of the Cape Verdes now.  Several long-range models develop this into a hurricane within a week".  Then again in the August 18 update: " The easterly wave I first mentioned four days ago is now near 35W and heading W at 12kts.  There is a 1009mb Low embedded within the wave, and its satellite presentation is impressive.  In the long term, it looks like continued W-WNW motion and gradually strengthening".  Gustav has been a long time in the making.

Elsewhere, we have a couple other areas of potential development.  One near 20N 56W (we've been discussing that one for a long time now), and one that recently exited Africa near the Cape Verde Islands.  The first has a 1011mb Low with it and is moving WNW, and the second has a 1008mb Low and moving WSW at 10kt.  The next names on the list are Hanna and Ike.  Ike replaces Category 3 Isidore (2002) that caused so much destruction on the northern Yucatan Peninsula, and then moved straight north into New Orleans as a tropical storm.

Please visit my tropical Atlantic headquarters.

25 August 2008

Fay gone, Gustav forms...

Long-lived Fay finally dissipated this past weekend, but not without drenching Florida and the southeast.  Past storms like Agnes '72 and Allison '01 come to mind when talking about weak systems that are slow and dump amazing amounts of rain.  You can view the estimated rainfall over the past week at http://water.weather.gov/index.php?layer[]=0&layer[]=1&layer[]=4&timetype=RECENT&loctype=STATE&units=engl&timeframe=last7days&timeYYYY=2008&timeMM=8&timeDD=25&product=observed&loc=stateFL

The easterly wave we were watching last week was upgraded to TD7 on Monday morning, then quickly upgraded again to TS Gustav, the seventh named storm of the season.  The intensity as of 21Z is 50kts and 996, tracking WNW at 12kts.  It is forecast to continue moving WNW and possibly intensify very quickly.  There is great disagreement between forecast models and the NHC forecast, so for now, I'll leave the details out.  The countries in its 3-day future are Haiti, Cuba, and possibly Jamaica.  If this storm manages to remain over ocean for longer than expected, it could become very intense given the ideal environmental conditions.

Elsewhere, there's a weak wave near 23N 56W, but vertical shear is strong over that system.

Please visit my tropical Atlantic headquarters.

19 August 2008

Fay inland over Florida and strengthening...

Fay made landfall on the Florida peninsula near Cape Romano (about halfway between Fort Meyers and Cape Sable) at 09Z this morning as a 50kt tropical storm.  However, since making landfall, it has developed an eyewall and the central pressures have fallen to 986mb (was 989mb at landfall, and 995mb a few hours prior to landfall).  Though the winds are not very strong at surface stations across the peninsula, they could start to increase in response to the decreasing pressure.

Visible satellite loop:

Radar loop:

The forecast is still uncertain.  The official forecast does bring Fay up to minimal hurricane strength, while tracking it northward over the peninsula, then westward over southern GA/AL.  http://www.nhc.noaa.gov/storm_graphics/AT06/refresh/AL0608W5+gif/094742W_sm.gif

But, as you can see here: http://euler.atmos.colostate.edu/~vigh/guidance/northatlantic/track_early1.png, there's a still a bit of model differences in the forecast track.  Some models bring it up to hurricane strength, even approaching CAT2-3 at landfall near the GA/FL border in a couple of days.

The easterly wave we've been tracking (exited Africa on Aug 13) is now at 38W and forecast to continue heading WNW and gradually strengthening.  This could be a big player in a week or so.  The next name on the list is Gustav.  

Please visit my tropical Atlantic headquarters.

18 August 2008

Fay heading for Florida...

During the weekend, Fay maintained tropical storm intensity while passing over Hispaniola and then central Cuba.  As of this writing, the circulation center has just exited Cuba and is now over very warm water south of the FL Keys.  Intensity as of 15Z today is 50kts and 1003mb, and it's moving NNW at 11kts.  SSTs under the storm are around 30C, and vertical shear is moderate: westerly at  10-15kts.

You will find a radar loop from Key West at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/fay08/Fay_18Aug08.gif

Also, you can monitor surface observations from Marathon FL at

Fay is forecast to pass directly over the Keys later today, as a tropical storm or possibly even a minimal hurricane, then continue north toward Tampa, making landfall there tomorrow morning (local) as a CAT1 hurricane.  The latest watches/warnings are shown graphically at http://icons-pe.wunderground.com/data/images/at200806_alerts.gif
After this west peninsula landfall, the long-range forecast isn't so straight-forward (some models take it on a north track inalnd over GA, others take it back over ocean and then into coastal GA/SC, while others take it for a loop off the east coast of FL, then back inland).  But let's get past this one first!

The easterly wave I first mentioned four days ago is now near 35W and heading W at 12kts.  There is a 1009mb Low embedded within the wave, and its satellite presentation is impressive.  In the long term, it looks like continued W-WNW motion and gradually strengthening.  This could be upgraded to TD7 today, and the next name on the list is Gustav.  There's also a wave right on its heels, near 25W which will also be watched closely for further organization.

Please visit my tropical Atlantic headquarters.

15 August 2008

Disturbance upgraded to Tropical Storm Fay, now near Hispaniola...

Yesterday through the present time, it tracked over the Virgin Islands, Puerto Rico, and is now over extreme eastern Dominican Republic (the eastern country on the island of Hispaniola).  Latest intensity is estimated at 35kts and 1009mb, and heading W at 14kts.  The track over Puerto Rico, Hispaniola, and eventually Cuba will certainly stall substantial intensification, but any opportunity over open water could be rapidly taken advantage of.

The track forecast has been most well-handled by the leading Canadian model, which has shown this system moving south of Cuba and into the Gulf of Mexico, while all of the others either recurved it east of Florida or up the eastern FL coast.  It's showing no rush to recurve, and is on a straight west heading, plowing right through the Greater Antilles.  Now, more and more models are indicating a path over or south of Cuba, then along or west of the FL peninsula.
A recent run from GFDL is shown here: http://moe.met.fsu.edu/cgi-bin/gfdltc2.cgi?time=2008081512-invest92l&field=Sea+Level+Pressure&hour=Animation (sea level pressure is contoured, runs out to 7 days)
This scenario has Fay passing south of Cuba, intensifying, THEN heading north toward the FL panhandle while intensifying, finally making landfall next Wednesday evening as a CAT3 hurricane.  This IS NOT an official forecast, just one model run, but something that warrants a close eye nonetheless.

The other easterly wave we've been watching for some time now is on its heels near 50W.  It's still disorganized, but is becoming more convectively active with time.

Please visit my tropical Atlantic headquarters.

14 August 2008

Depression nearly formed near Virgin Islands...

Though still not officially a Depression, the easterly wave we've been watching closely is now passing north of Barbuda and toward the Virgin Islands.  You can view a radar loop of the forming storm from the Guadeloupe radar at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/fay08/Fay_14Aug08.gif

It has entered the phase where it can intensify rather quickly, a phase visually triggered by the development of a persistent CDO, or cold dense overcast.  On an infrared satellite loop, this looks like a shield over the center, with very cold cloud-top temperatures, roughly -75C in this case.
Under this dense cloud shield aloft, a core of intense thunderstorms is organizing, perhaps even into an early eyewall (see radar loop above).

Current intensity is estimated at 30kts and 1009mb, and tracking WNW at 12kts.  The forecast is looking more and more ominous for the US, and first, the Bahamas.  Computer models indicate a track directly over the Bahamas, maybe as a CAT1 hurricane this weekend.  By early-mid next week, the southeast US coast should be on alert... from FL to NC.  There is a smaller possibility that it could slip south of Florida and cross into the Gulf.  The forecast track will of course be closely scrutinized in the coming days.

The next number/name on deck is 6/Fay.

Elsewhere, an impressive easterly wave has just exited the African coast and is just south of the Cape Verdes now.  Several long-range models develop this into a hurricane within a week.

Please visit my tropical Atlantic headquarters.

12 August 2008

Two easterly waves tracking across the basin...

Although there are no named storms at the moment, I wanted to point out a couple easterly waves.  One is centered near 54W, and the other near 31W.  Both have Lows associated with them, with approx 1008mb central pressures, and both are traveling W-WNW at 10-15kts.  You can track them in 12-hourly satellite images at:

The western one is forecast to gradually turn more westward, and be just north of Hispaniola in 4-5 days.  The eastern one is forecast to continue heading WNW-NW.  Both should strengthen, but the western one is favored... AND of more concern to the US.  By week's end, a 5-day forecast could be quite revealing: is it destined for a landfall or not?

And what exactly IS an easterly wave?  First of all, it's "easterly" because it travels from east to west, with the trade winds (the equatorial/tropical belt of winds that blow from east to west all year long).  The "wave" part has more interesting origins.  Large temperature differences between the desert and rainforest regions of continental Africa generate a strong low-level jet, or plume of enhanced winds.  This jet is unstable, and tends to break down into discrete waves, with ridges and troughs.  The troughs are what we then call "easterly waves", and are characterized by lower pressures and thunderstorms.  The jet is most active in the August-September timeframe, but is present from April through November.  As you've probably noticed, not all easterly waves develop into tropical cyclones.  Roughly 60 easterly waves track across the basin each season, but on average, only 6 or 7 of them might become tropical storms or hurricanes.

Please visit my tropical Atlantic headquarters.

05 August 2008

Edouard makes landfall...

Edouard made landfall as a 55kt tropical storm Tuesday morning around 7am CDT, between Sabine and High Island TX ... right by the Louisiana border.  Fortunately, this area is not very populated.  Jefferson County, where landfall occurred, has about 240,000 residents, compared to about 4 million in the three neighboring counties to its west.  However, in the same county, about 1 in 5 people live at or below poverty level, so even a weak storm can have a very negative effect.  Incidentally, this is almost exactly where Rita made landfall 3 years ago, but as a Category 3 hurricane with 105kt winds.

So far, no major damage reports have come out, and no deaths... just half a foot of rain and moderate gusty winds that have taken down some trees and power lines.  The rest of the basin is quiet right now, and probably will be for a little while longer.

Please visit my tropical Atlantic headquarters.

04 August 2008

Edouard forms near northern Gulf coast...

On Sunday afternoon, TD5 formed in the north central Gulf of Mexico.  It is currently just south of New Orleans and heading W at 7kts... near 28.2N 90.6W.  Intensity is 40kts and 1002mb.  It's battling some northerly wind shear and ambient dry air, which should both act to at least slow intensification.  But SSTs are quite warm under its future track.

Latest SST analysis:
Latest vertical shear analysis:

A Tropical Storm Warning and a Hurricane Watch are in effect for the northern half of the TX coast and the western half of the LA coast.  Edouard is not forecast to be a hurricane at landfall, but it's certainly not out of the realm of possibilities.  It is heading generally westward toward Houston, and should make landfall early Tuesday morning.

Please visit my tropical Atlantic headquarters.

30 July 2008

Strong easterly wave exits Africa...

An easterly wave that was "born" one week ago over the Ethiopian Highlands exited the African coast yesterday and quickly got organized. It's now just a couple hundred miles off the coast, halfway to the Cape Verde Islands at approximately 16N 21W.  It has a 1006mb Low embedded within it, and is tracking W at 15kts.  However, it is forecast to curve toward the WNW-NW and into higher shear and cooler water.  The SST now is only around 26C, but could drop to 24C in the next couple of days.  It would become TD5 or TS Edouard if it can strengthen before the environmental conditions deteriorate.

Please visit my tropical Atlantic headquarters.

23 July 2008

Dolly making landfall...

Dolly has strengthened overnight, and is now just miles from the coast (at 16Z) and is a Category 2 hurricane... 85kts and 964mb.  Though only 40 miles or so offshore, the eyewall (the engine that drives the rest of the machine) is still over very warm Gulf water.  As such, the storm can still continue to strengthen while the entire western half of the storm is over land.  The eye is presently located 40 miles ENE of Brownsville TX and is ~23 miles across.

Rainfall totals could reach one foot.  Storm surge is in the 4-6 foot ballpark.  It's still too early to know the full aftermath, as it's still in progress.  Buoy 42020, offshore between Brownsville and Corpus Christi, is reporting 22' waves, and the worst is still coming.

It's moving very slowly (about 6kts) and is now heading nearly parallel to the coast, which means Dolly could still have several hours over water.  If you navigate to the link below, you'll find links to radar loops, surface observations, and satellite imagery.

Hardly worth discussing, Cristobal is now a disorganized extratropical storm south of Newfoundland.

The easterly wave near the Cape Verdes has degenerated quite a bit and is now much less of a concern.  It will be monitored for signs of redevelopment.

Please visit my tropical Atlantic headquarters.

P.S.  You can all consider yourselves more educated than CNN, who claims that Dolly is the second storm of the Atlantic season.  Hard to reach "D" after only two storms!  Granted, it is the second HURRICANE, but not the second storm.  Details, details....

22 July 2008

Cristobal heading out to sea, Dolly heading for land...

Cristobal is now east of Cape Cod, south of Nova Scotia, and is a 55kt tropical storm.  It will continue heading generally eastward into the north central Atlantic and should only be a tropical system for another day or two.

Dolly, on the other hand, is of much greater concern.  Over the last 18 hours, the huge rainband that was far removed from the center has dissipated in favor on centralized deep convection.  This is the needed ingredient for strengthening: focusing the latent heating over the center.  The latest intensity is 60kts and 991mb, and is getting closer to hurricane status every hour.  It's also getting closer to landfall every hour... now just 200 miles southeast of Brownsville and heading NW at 10kts.  Landfall is expected early tomorrow morning near Brownsville as a hurricane.

Intensity at landfall is a tricky thing... the storm is showing every sign of rapid intensification, and it's at the classic current intensity to begin RI.  Vertical shear is basically negligible, and SSTs are 29C+.  So the problem is how fast will Dolly intensify on its approach?  NHC is forecasting landfall at 80kts, which is line with the model guidance, but models (and people) don't forecast RI well.

You can already see outer rainbands approaching the coast, and the eyewall is coming into view as well:
I will also keep a running loop of the short-range Brownsville radar at: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/dolly08/Dolly_22-23Jul08.gif
The latest watches and warnings for Texas and Mexico are plotted graphically at:

And the easterly wave that exited Africa yesterday is looking very impressive.  It's now near the Cape Verde islands, and is consolidating its circulation.  It has a 1009mb Low, and is moving W at 15kts.  It is not forecast to intensify real quickly, but very gradually, and continue heading W-WNW.

Please visit my tropical Atlantic headquarters.

21 July 2008

Bertha finally gone, Cristobal and Dolly form, new wave off Africa...

The final advisory was written on Bertha on Sunday morning.  It's now an extratropical cyclone over Iceland.  It was around for 17.25 days, the new longest-lasting July storm.  It also set a record for furthest east formation in July.  Bertha, with the help of the rest of the month, has elevated the 2008 season to the ranks of the 1916, 1926, 1933, 1961, and 2005 seasons so far.  These were some of the most active seasons on record.

In what is rapidly starting to look like a substantial hurricane season, Cristobal formed from the disturbance that was located off the GA coast on Friday, and Dolly formed from what was the long-tracked easterly wave that was in the western Caribbean on Friday.  Both are tropical storms now, and both are forecast to intensify.

Cristobal is located around 200 miles ENE of Cape Hatteras NC with an intensity of 55kts and 1000mb.  It is forecast to strengthen slightly, perhaps to minimal hurricane, but head northeast toward Newfoundland by Wednesday.  The satellite presentation is not so healthy.  It has centralized cold cloud tops, but is very compact and sheared.

Dolly, on the other hand, looks more substantial.  After watching it struggle for 10 days, it finally got named near the Caymans on Sunday at 12Z.  It has since crossed the Yucatan Peninsula as a TS, and is now in the Gulf heading for southern Texas.  It's a large system, but lacking centralized deep convection right now.  All of the convection is in a hefty rainband wrapping 3/4 of the way around the center.  Latest intensity is 45kts and 1005mb.  It's heading WNW at a brisk 16kts, and landfall is expected on Wednesday as a fairly strong hurricane.  Environmental conditions in the western Gulf would allow for rapid strengthening.  A Hurricane Watch has been issued from Brownsville to Port O'Connor.

Lastly, a new very strong easterly wave is just exiting Africa and has the potential to develop quickly once over the ocean.  There is a 1007mb Low embedded within a broad mid-level circulation centered near 15N 15W.  The next number/name in deck is 5/Edouard.

Please visit my tropical Atlantic headquarters.

18 July 2008

Bertha still lingering, two other disturbances getting organized...

Bertha is still a tropical storm, and is now about 700 miles south of Newfoundland.  The first advisory on Bertha was written on July 3, over two weeks ago!  Phil Klotzbach here at CSU points out that this is now the longest-lived storm in the Atlantic since Alberto '00 at 15.25 days.  It has smashed the record for longest-lived July storm.

Latest intensity is 55kts and 995mb and tracking NE at 16kts.  It still has a very impressive satellite presentation, with a renewed attempt at forming an eyewall and eye.  However, this last-minute perk comes a day or so before it encounters hostile shear and cold ocean temperatures.  It should transition to an extratropical cyclone by the end of the weekend.

Elsewhere, things are getting active.  The easterly wave I first mentioned 9 days ago and have been keeping you updated on (the one that recently passed by the Windwards) is now just north of western Venezuela and has a lot of deep convection near the center of the mid-level circulation.  There is a 1008mb Low embedded in the convection.  Given its location and potential for strengthening, the western Gulf coast has a very long-range heads-up (could be 6-7 days out... IF it makes it). 

Closer to the US, there's a circulation with associated convection just offshore of Georgia.  Conditions are also favorable for this to develop... a huge boost for it is its position directly over the warm Gulf Stream.  You can see it from the Charleston SC long-range radar: http://radar.weather.gov/radar.php?product=N0Z&rid=clx&loop=yes
It is expected to basically track N-NE along the length of the east coast, which is dangerous if it decides to quickly strengthen!

The next names on the list are Cristobal and Dolly.

Please visit my tropical Atlantic headquarters.

Bertha still lingering, two other disturbances getting organized...

Bertha is still a tropical storm, and is now about 700 miles south of Newfoundland.  The first advisory on Bertha was written on July 3, over two weeks ago!  Phil Klotzbach here at CSU points out that this is now the longest-lived storm in the Atlantic since Alberto '00 at 15.25 days.  It has smashed the record for longest-lived July storm.

Latest intensity is 55kts and 995mb and tracking NE at 16kts.  It still has a very impressive satellite presentation, with a renewed attempt at forming an eyewall and eye.  However, this last-minute perk comes a day or so before it encounters hostile shear and cold ocean temperatures.  It should transition to an extratropical cyclone by the end of the weekend.

Elsewhere, things are getting active.  The easterly wave I first mentioned 9 days ago and have been keeping you updated on (the one that recently passed by the Windwards) is now just north of western Venezuela and has a lot of deep convection near the center of the mid-level circulation.  There is a 1008mb Low embedded in the convection.  Given its location and potential for strengthening, the western Gulf coast has a very long-range heads-up (could be 6-7 days out... IF it makes it). 

Closer to the US, there's a circulation with associated convection just offshore of Georgia.  Conditions are also favorable for this to develop... a huge boost for it is its position directly over the warm Gulf Stream.  You can see it from the Charleston SC long-range radar: http://radar.weather.gov/radar.php?product=N0Z&rid=clx&loop=yes
It is expected to basically track N-NE along the length of the east coast, which is dangerous if it decides to quickly strengthen!

The next names on the list are Cristobal and Dolly.

For the latest on the developing depressions in the Caribbean Sea and off the US east coast, please visit http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/
I added a feature for the batch of real-time images... in the visible and infrared floaters (bottom center and bottom right), you can view different storms by simply placing your cursor over the name of the one you wish to see.  Clicking on one of the names will take you to the full-sized version of the image.  The numbers are identified in the track plot (lower left of the page's images).

Please visit my tropical Atlantic headquarters.