22 August 2007

Dean makes second Mexico landfall...

At about 17Z today, Hurricane Dean made landfall (again) between Tampico and Veracruz.  Dean exited Yucatan as a 70kt storm, barely holding onto hurricane status, but reintensified to an 85kt CAT2 storm prior to this morning's landfall.  So far, 11 deaths have been blamed on Dean throughout the Caribbean and Central America.  It spent 4 full days as a major hurricane, which is nearly the normal SEASONAL total of "intense hurricane days".

The strip in the Caribbean along Dean's path is now 1-3C cooler than it was a week ago, a feature refered to as a "cold wake".  This happens for slow and/or intense storms, particularly over warm water that doesn't extend very deep.  The  monstrous waves do a lot of mixing, and although the top several meters might be very warm, the ocean is cooler below, and after an extreme mixing event (like a CAT4 hurricane), the cooler waters below are upwelled, leaving the cold wake.  This time of year, the waters can be quick to recover (perhaps a week or so).

That page shows a 15-day loop of SSTs in the Caribbean; areas with persistent cloudiness during that day do not have retrieved SSTs and are shown as white blotches.  You can easily track the cloudiness associated with Dean across the Caribbean from the 17th-20th.

Please visit my tropical Atlantic headquarters.

21 August 2007

Dean hits Mexico as a CAT5 storm...

At around 09Z this morning, Dean hit the Yucatan Peninsula near the town of Mahahual as a Category 5 hurricane with 145kt sustained winds.  The minimum central pressure was 906mb, and the eye was 15 nautical miles across.  To put that in perspective, if you were floating (passively) in the eyewall, you'd make a full trip around the eye in just 17 minutes!!  There's a radar loop of landfall available here:
This is the most intense hurricane in the Atlantic since Wilma 2005 (which coincidentally also hit Yucatan).

Fortunately, coastal residents had been evacuated, and the storm passed through a rather unpopulated section of the peninsula, and as of this writing, no casualties have been reported in Mexico.

The buoy that I mentioned yesterday to the north of Dean's track recorded a peak significant wave height of 37 feet!  By definition, "significant wave height" is the average height of the highest 1/3 of the waves... NOT the highest wave height reached.

Dean will exit the peninsula in a few hours and enter the Bay of Campeche, then make a second Mexican landfall in central Veracruz tomorrow morning as a CAT2-3 hurricane.  As of 15Z, the intensity is 90kts and 950mb, and continuing to weaken as it traverses the land.

The easterly wave I pointed out yesterday has been tracking WNW, and is now east of the Bahamas and north of Dominican Republic (~26N 67W).  It is still not very well organized, but most statistical models and a few dynamical models develop it and bring it NW toward the US, so it will be watched over the coming days.

Please visit my tropical Atlantic headquarters.

20 August 2007

Update on Dean

There's a radar loop showing Dean's approach to the Yucatan Peninsula available at: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/dean07/Dean_20Aug07.gif

Dean will also pass about 75 miles south of a buoy in a few hours (around 23Z)... the buoy reports wave height, pressure, wind speed/gusts, etc.  Although it won't be a direct overpass, we'll get some idea of the near-core environmental surface conditions.

Wave height:
Surface Pressure and winds:

The intensity as of 18Z is 130kts and 924mb.
Storm surge along the northern Yucatan Peninsula is expected to reach 12-18 feet above normal.  Dean is forecast to become a CAT5 hurricane later today/tonight.

Please visit my tropical Atlantic headquarters.

Dean hits Jamaica, heads for Yucatan...

Over the weekend, Dean achived maximum CAT4 intensity (130kts) with a low central pressure of 918mb.  It scraped by Jamaica yesterday afternoon/evening, with the eye remaining offshore but the northern eyewall brushing the island. Jamaica faired rather well, with the primary damage being infrastructure.  Dean has claimed at least 7 lives so far though, in Martinique, St. Lucia, Dominica, and Haiti.

The position at 15Z was 17.9N 82.4W and heading west at 18kts.  Intensity is 130kts and 925mb.  Hurricane warnings are in effect for the Caymans, the Yucatan Peninsula (east and west sides), and Belize.

Dean is in an environment that could barely be more conducive to strengthening.  It is expected to reach CAT5 status in time for landfall on the Yucatan Peninsula and northern Belize Tuesday morning.  SSTs are presently around 29C and expected to increase to 30C by landfall.  Vertical shear is minimal, but should pick up quite a bit in the Bay of Campeche, limiting Dean's intensity for its second Mexican landfall.

http://einstein.atmos.colostate.edu/~mcnoldy/tropics/hovmoller/atlantic/ shows a nice progression of Dean and the waves behind Dean.  The images on there are slices of IR imagery 12 degrees high by 80 degrees wide, every 12 hours for 7 days, with the newest on top.

There's a potent easterly wave trying to get organized in the central Atlantic; it left the African coast back on August 15 and is now located about 2000km east of the Bahamas and is moving west at 18kts.  Most models do not develop it, but the few that do REALLY do... the next name on deck is Felix.

Please visit my tropical Atlantic headquarters.

17 August 2007

Dean rapidly intensifying west of the Lesser Antilles...

At about 10Z this morning, Hurricane Dean crossed the Lesser Antilles, between Martinique and St. Lucia (one side of the eyewall on each).
Martinique experienced severe conditions, with wind gusts up to 120mph, 30-foot waves, and 4"/hr rainrates.

Dean is now in the west central Caribbean and gaining strength very quickly. The latest intensity as of 18Z is 110kts and 961mb, making it a strong CAT3 hurricane (almost CAT4).  There appears to be almost nothing to hinder further intensification this weekend.

In the past 24 hours, the maximum sustained winds have increased 30kts and the central pressure fell 18mb.  The hurricane now has an open eye 15 nautical miles across.

It is expected to travel WNW across the Caribbean, hitting Jamaica on Sunday evening and Cancun on Tuesday morning, both as a very powerful and dangerous hurricane.  By mid-late next week, all interests in the western Gulf should be prepared for Dean, from Mexico to Louisiana.

Please visit my tropical Atlantic headquarters.

16 August 2007

Dean rapidly gaining strength, Erin makes landfall...

Dean has internsified substantially over the past 24 hours, and at 09Z this morning was upgraded to the first hurricane of the season.  In the past day, maximum sustained winds have increased by 30kts and the MSLP fell 18mb.  The satellite presentation is nearly flawless now, with symmetric outflow aloft, deep covection over the center, and an eye that's 90% formed.

Hurricane Dean is presently located at 13.9N 55.5W and as of the 15Z advisory from NHC the intensity was 80kts and 979mb. It's moving briskly to the west at 21kts.  The forecast is for continued intensification, crossing the Leeward Islands tomorrow morning as a strong CAT2 hurricane, then passing near Jamaica on Sunday as a strong CAT3 hurricane.  The current forecast has a direct hit on Cancun as a CAT4 storm early Tuesday morning.  Hurricane Watches and Warnings are in effect for nearly all of the Leeward Islands.

For those who are interested, you can view a radar loop (adding new frames every 15 minutes) of Dean's passage through the central Leeward Islands at:

It should pass over the islands at about 6am EDT.
Erin made landfall early this morning near Corpus Christi, TX as a minimal Tropical Storm.  The storm is now inland and weakening quickly, with the remaining threat being heavy rain.
There is a radar loop of Erin making landfall available at

Please visit my tropical Atlantic headquarters.

15 August 2007

Dean and Erin both strengthening...

TS Dean has shown a solid trend of intensification, though not rapid yet.  An important transition has taken place where scattered deep convection has given way to more concentrated centralized deep convection.  The core appears to be trying to form the beginnings of an eyewall at the time of this writing (18Z).

Dean's intensity was estimated at 50kts and 997mb at 15Z.  The heading is W at 17kts.  Vertical wind shear is fairly low (10kts) from the north and should decrease as time goes on.  SST is around 27.5C and will increase to 30C over the next 5 days.

The latest long-range forecast takes Dean through the central Lesser Antilles in two days, south of Hispaniola in 4 days, and near Jamaica in 5 days, all as a strong or major hurricane.  Recent model runs suggest that the trough off the US east coast will not be as potent as suspected yesterday, which means that the hurricane is less likely to be nudged northward out of the Caribbean Sea.

At 15Z today, TD5 was upgraded to TS Erin in the central Gulf of Mexico. Intensity as measured by aircraft is 35kts and 1005mb.  It's over 30.5C water which is more than ample for a storm to fuel itself, and vertical shear is neglibly small.  However, the thing working against it for further intensification is time.  In one day, it will be onshore near Brownsville TX.  A Tropical Storm Warning is already in effect for the southern half of the TX coast.

Please visit my tropical Atlantic headquarters.

14 August 2007

TD4 upgraded to TS Dean...

Yesterday's new Depression continued to get better organized, and despite the moderate easterly wind shear, has strengthened into the season's 4th named storm, Dean.  Convection has been deep and persistent over the center, though still slightly displaced to the west.  At 15Z today, TS Dean was located at 11.7N 39.4W (about 2100km east of the Lesser Antilles) and heading due west at a brisk 20kts.  Satellite-estimated intensity is 35kts with 1004mb MSLP.

The forecast is seemingly easy over the next several days: keep moving W-WNW and intensify.  The latest forecast models indicate a significant trough forming off the US east coast, allowing Dean to nudge northward over the weekend, perhaps over the Virgin Islands and Puerto Rico as a major hurricane.  Dean could also pose a threat to the mainland US late next week.  I should note that the NHC forecast track is a northern outlier compared to computer model forecast tracks... meaning that they are subjectively putting a lot of confidence on that trough being very influential.

Elsewhere, the disturbance I mentioned in the southeast Gulf of Mexico is still getting its act together, and is drifting northwest toward the US/Mexico border.   It's near the northwest tip of the Yucatan Peninsula with a 1007mb Low.  It doesn't seem too likely now that it will be a major threat, but certainly must be watched very closely.  It could become a TS within the next 24-36 hours and make landfall as TS Erin.

Please visit my tropical Atlantic headquarters.

13 August 2007

Forth Tropical Depression forms in deep tropics...

At 15Z today, the easterly wave that exited the African coast on Friday was upgraded to Tropical Depression 4 based on satellite imagery.

TD4 is presently experiencing moderate vertical shear (15-20kts) which is keeping the low-level center east of the coldest cloud tops.  The shear should lessen over the next few days, and combined with SSTs in the 28-29C ballpark, allow it to drastically intensify.  It's located at 12.0N 31.6W (about 600km southwest of the Cape Verdes) and zipping along to the west at 18kts.  The estimated MSLP is 1005mb and winds are 30kts.

The present forecast track shows continued movement toward the W-WNW, reaching the Leeward Islands by Friday night into Saturday morning.  The forecast intensity from NHC is a tad conservative in my opinion, but reasonable.  It shows gradual intensification, reaching minimal hurricane intensity on Friday morning, and CAT2 by Saturday.  Off the official record though, the potential exists for much more rapid development.  The next name on the list is Dean.

Also of great interest is an area of disturbed weather in the southeast Gulf of Mexico near the western tip of Cuba, being invigorated by a cold upper-Low to its northwest.  This sort of system is not well predicted, and can develop fairly quickly, so I'd venture a guess that Floridians would want to keep a close eye on things there.

Please visit my tropical Atlantic headquarters.

02 August 2007

Strong wave enters the Caribbean...

The system is now in the southeast Caribbean, south of Puerto Rico, and sporting a very large cold CDO.  It has sped up, tracking W at 20kts, and entering a climatologically unfavorable area for development due to strong vertical wind shear (home of the 20-30kt Caribbean low-level jet AND sometimes an upper-level TUTT, or Tropical Upper Tropospheric Trough).  However, there is a remote chance that it could develop there (not unprecedented); otherwise, wait until it's through and in the western Caribbean.
With the exception of the temporary increased shear in its near future, conditions are very favorable for intensification to a TS and hurricane during the weekend.  The model track guidance suggests a W-WNW path toward Mexico.

An easterly wave on the coast of Africa will also bear watching over the coming days.

Please visit my tropical Atlantic headquarters.

01 August 2007

Chantal dissipates... TD4 in the making?

The final advisory was written on TS Chantal last night, at an intensity of 45kts and 994mb.  The storm was absorbed by the mid-latitude trough as expected and the remnants are near Newfoundland now.

However, the easterly wave approaching the Leeward Islands has gotten much better organized, with a more compact mid-level circulation and more persistent deep convection.  It's now near 13N 58W or very close to Barbados and an aircraft recon flight into it is scheduled later today.  Conditions are favorable for it... fairly low vertical shear, and SSTs are presently 27.5C and will increase to 28.5C+ over the next few days as it tracks westward through the Caribbean.  This has the potential to be a TS by tomorrow and the season's first hurricane by the weekend.  The next name on the list is Dean.

The wave that exited Africa yesterday is now near the Cape Verde Islands and shows signs of increased organization; a 1009mb Low is associated with it with spotty convective bursts.

Please visit my tropical Atlantic headquarters.