Strong tropical wave blows into the Lesser Antilles

By: Dr. Jeff Masters , 1:29 PM GMT on August 24, 2006

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A powerful tropical wave that has the potential to become a serious hurricane is sweeping through the southernmost Lesser Antilles Islands today, bringing tropical storm force wind gusts and heavy rains. Barbados reported sustained winds of 32 mph at 5am this morning. Togabo had wind gusts to 36 mph, and wind gusts to 43 mph were observed on St. Lucia. A QuikSCAT satellite pass from 6:30am EDT shows a large area of 35 mph winds to the north of the center, which appears to be near 11N 59W, near the islands of Trinidad and Tobago and just off the South American coast. The storm's organization has steadily increased since yesterday, and the Hurricane Hunters are tasked to investigate this afternoon to see if a tropical depression has formed. The storm has two main areas of intense thunderstorms visible on satellite imagery this morning that are almost disconnected. I expect the northern mass will dissipate today, since it is much farther from the center of circulation.

Wind shear is favorable in a small area over the storm--5-10 knots--and is forecast to remain low through the next five days. However, there is a zone of very high shear to the system's north, so the forecast of low shear could easily change. A large area of dry air and Saharan dust covers much of the eastern Caribbean, and may be a modest impediment to intensification. The primary difficulty for the storm lies in its close proximity to South America. The storm center may hug the coast through Saturday, limiting its development. The storm should bring heavy rains and winds near tropical storm force over the ABC Islands of Aruba, Bonaire, and Curacao on Friday. After that, there is a lot of uncertainty.

The computer models
The latest 8pm and 2am EDT computer model runs have a variety of solutions. The Canadian model continues to be very consistent and very gung-ho, developing 97L into a strong tropical storm on Saturday, south of Jamaica, then taking the storm into the Gulf of Mexico as a hurricane. The NOGAPS model is also consistent, assuming a more southerly track will occur with no development due to close proximity to the South American coast. The GFS takes a weak tropical storm across the Dominican Republic on Saturday, then into the Bahamas. The GFDL has the same idea, but has a much stronger system that becomes a Category 1 hurricane in the Bahamas on Monday.

The run-to-run consistency of the GFDL has been poor, and both the GFDL and GFS have not done a good job forecasting the initial track of the storm so far. A more southerly track betwen Jamaica and Honduras like the Canadian and NOGAPS models are suggesting is probably more reasonable. If 97L can survive the next two days and separate from the South American coast--which it has at least a 50/50 chance of doing--I believe it will probably develop into a serious hurricane, as the GFDL and Canadian models have been suggesting. The track such a hurricane might take is highly uncertain, but it appears that Jamaica, Cuba, and the Yucatan would be at highest risk in the Caribbean. No part of the U.S. coast can be ruled out as a target in the longer term.

Got travel plans to the Caribbean this week? Don't change them yet. This appears to be an all-or-nothing kind of situation, and we could get nothing. It may not be until Saturday that we have a reasonable idea if this storm will be a major threat.


Figure 1. Current satellite image of Invest 97L.


Figure 2. Preliminary model tracks for disturbance 97L approaching the Lesser Antilles Islands.

Debby
Tropical Storm Debby remains a minimal tropical storm today, but is expected to slowly intensify in response to some warmer waters along her path the next two days. By the time Debby turns north this weekend, she could attain hurricane status. Early next week, Debby is expected to get caught up in the jet stream and die in the North Atlantic.

I'll have an update this afternoon after the Hurricane Hunters check out 97L.

Why the 2am run of the GFDL failed
The 2am EDT run of the GFDL model failed on 97L this morning, so I was quoting the results from the 8pm EDT run last night. I got an email from Morris Bender of the GFDL project this morning on why the 2am GFDL run failed:

The vortex initialized from our initialization was very weak as the initializaiton process spins up the storm to match the observed initial winds. Since the easterlies in the lower level were very strong in the GFS analysis, it initialized a disturbance with very weak vorticity.

As you can see at hour 0 there was almost no circulation intially. As a result, our grid movement shut down at 3 hours and the inner nests could no longer follow the storm for the rest of the forecast.

The previous runs also had a very weak initial disturbance but there was enough of a pressure gradient that the inner nests continued to follow the vortex and eventually with the high resolution it developed into a signficant tropical cyclone.

In the 6z run, the weak distrubance moved out of the high resolution inner grid, into the coarse resolution, and so all we had left was a very weak disturbance that could not be resolved in the corase outer mesh.


As you can see, getting the computer models to work on weak disturbances is a difficult business! We should not put too much faith in the computer models for any weak system; it is too difficult for the models to get the starting conditions of the storm correct.

Jeff Masters

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417. cajunkid
5:08 PM GMT on August 24, 2006
there is no eye...lol...if anything 97L has a steep uphill battle...look at the dry air Link
Member Since: July 10, 2005 Posts: 3 Comments: 1279
416. emagirl
4:58 PM GMT on August 24, 2006
well i am gone to lunch i will catch up with you guys in an hour
415. tropicallydepressed
4:58 PM GMT on August 24, 2006
OMG! Is that an eye forming in 97L?
Member Since: August 11, 2006 Posts: 0 Comments: 137
414. FierceWinds
4:57 PM GMT on August 24, 2006
alaina1085, right now.
413. alaina1085
4:55 PM GMT on August 24, 2006
What time is recon flying this beast?
Member Since: August 2, 2006 Posts: 0 Comments: 1240
412. Cavin Rawlins
4:54 PM GMT on August 24, 2006
Atlantic Today
The large continental Upper Level High (ULH), that was centered over the USA has broken into two centered areas, due to a 200mb polar trough. The first one is centered over Northern Texas, the other centered over Florida.
On the Eastern periphery of the latter high is an elongated Upper Level trough, extending from the North Central Atlantic, southwestward towards the Central Bahamas. There are two upper level lows located along the trough, at 35N and 22N. The one at 22N is producing numerous showers over the South central Bahamas Islands.

There is an upper level low located south of New Orleans, Louisiana, along the ULH over Florida is helping to produce numerous showers and thunderstorms cross the entire Gulf of Mexico, the Gulf Coast States and Eastern Mexico.

The Eastern Caribbean Sea is dominated by Upper Level Ridging in associated with a large Upper Level High centered east of Trinidad. The NW quadrant of the ULH and some SE flow extending from the Upper Level trough near the Bahamas is generating strong wind shear in the Atlantic and Caribbean Sea and, just north and east of the Islands. This high is moving in the general direction of 97L, helping to create Upper Air divergence and low wind shear around the area of 97L.

A tropical wave is inland over Central America and another is the South Caribbean Sea, south of Haiti, moving west.

A central Atlantic Tropical Wave (97) accompanied by an area of low pressure (1009mbars), with its axis along the ITCZ at 60W, has increased in shower activity and organization today. The wave is producing numerous showers and thunderstorms across the Windward Islands, Trinidad and Tobago and Barbados.

Discussion of 97L
The Upper Air atmosphere is quite favorable for development, with Upper Level Water Vapor and Upper Air Divergence both favorable.

There is some strong Upper Level Winds north of 97L, that forecast to decrease as the ULH moves NW.

Future of 97L
If 97L will continue to move WNW, into the SE Caribbean Sea into more favorable environment, as dry air decreases into the Caribbean Sea.

Surface Observations
Sea Surface Temperatures are above 80 degrees in the area.

Waves are 5-10 feet approaching the Windward Islands.

Buoys/Ships
Bouy C6EN4, located in the SE Caribbean Sea, measured a central pressure of 1012.5mbars and winds from the NE at 20knots.

Land-Based Stations at 12PMAST
POINT, Grenada (TGPY)
Pressure:1010mbars
Winds: SSW at 4m/s

CROWN, Trinidad and Tobago (TTCP)
Pressure: 1010.8mbars
Winds: SSW at 6m/s

Grantley Adams, Barbados
Pressure: 1012mbars
Winds: SE at 44km/h.

A subtropical surface high is located SE of Bermuda, at 30N/57W, with surface ridging seen all the way to the SE United States. This will be help steering 97L to the NW in time.

At 11amAST, Tropical Storm Debby was located 20.4N, 37.8W, in the open Atlantic. The tropical storm is moving WNW at 19mph. Debby has winds of 50mph and a central pressure of 1000mbars. It is forecast to continue moving WNW around a ridge (associated with a stronger High in the North Atlantic) then NW as the ridge is weakened by a Central Atlantic Upper Level trough. Debby could become the seasonís first Hurricane.

By Weather456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
411. hurricane23
4:52 PM GMT on August 24, 2006
Guys i think 97L will be a short lived system as there is between 25-30kts of shear to west of this mess.SEE HERE
Member Since: May 14, 2006 Posts: 8 Comments: 13804
410. TampaWeatherBuff
4:48 PM GMT on August 24, 2006
Every time I get excited about a tropical system like Wants-to-be-Ernesto (97L), they go poof or otherwise go somewhere else.

So I'm adopting an unreasonably and reflexively knee-jerk skeptical stance on every system for the rest of this year. Starting with this pathetic, useless, wimpy, going-to-get-blown-apart blob.

Wants-to-be-Ernesto is going to fizz away, and if it doesn't, it's going to whiz by the West or North gulf states as a passing drizzle, and miss Tampa altogether.

That's not a forecast, that's a prediction!

;)
Member Since: October 19, 2005 Posts: 14 Comments: 188
409. hurricane23
4:48 PM GMT on August 24, 2006
(Guys here is a close visible pic of 97L)





Member Since: May 14, 2006 Posts: 8 Comments: 13804
408. FierceWinds
4:44 PM GMT on August 24, 2006
fran1983 at 4:38 PM GMT on August 24, 2006.
It looks like it starting to get some wrap around the center, somewhat. Anybody else see this?


Definitely. I believe it's main impediment may be the dust to it's west. Link
407. FierceWinds
4:41 PM GMT on August 24, 2006
For some reason I just have the feeling that 97L will be getting really big. Scientific data aside, anyone else feel the same thing?
406. StormJunkie
4:41 PM GMT on August 24, 2006
New Blog is up!!!
Member Since: August 17, 2005 Posts: 26 Comments: 16866
405. Bamatracker
4:40 PM GMT on August 24, 2006
it sort of looks to me like the surface rotation seen by the visible satellite is trying to race away from the convection.

Link
Member Since: May 17, 2006 Posts: 6 Comments: 1367
404. fran1983
4:38 PM GMT on August 24, 2006
It looks like it starting to get some wrap around the center, somewhat. Anybody else see this?

http://www.ssd.noaa.gov/goes/flt/t2/loop-avn.html
403. Bamatracker
4:38 PM GMT on August 24, 2006
so on the flight...what are we watching besides wind speed. Cant something be told about a storm from the temps and dew points aswell?
Member Since: May 17, 2006 Posts: 6 Comments: 1367
402. StormJunkie
4:38 PM GMT on August 24, 2006
WB, the E coast area is currently moving away from land, but the GFS hints at it getting pushed back in a couple of days.
Member Since: August 17, 2005 Posts: 26 Comments: 16866
401. Bamatracker
4:35 PM GMT on August 24, 2006
oh sweet link thelmores!!
Member Since: May 17, 2006 Posts: 6 Comments: 1367
400. FierceWinds
4:35 PM GMT on August 24, 2006
Posted By: hurricane23 at 4:25 PM GMT on August 24, 2006.
Looks to me like shear is really affecting 97L right now.


I'm not sure if the sheer is affecting it that much. It may be the Saharan dust to 97L's west.
399. thelmores
4:34 PM GMT on August 24, 2006
google earth from storm2k
Member Since: September 8, 2005 Posts: 0 Comments: 3805
398. PascMississippi
4:33 PM GMT on August 24, 2006
Have ya'll seen Dr M's update?
397. Bamatracker
4:33 PM GMT on August 24, 2006
here is an update from the flight

During reconnaissance of tropical system INVEST a maximum sustained wind speed of 32 mph at 1004 feet, and a maximum wind gust of 34 mph at 1004 feet, were found by the government plane.
Member Since: May 17, 2006 Posts: 6 Comments: 1367
396. thelmores
4:31 PM GMT on August 24, 2006
672
SXXX50 KNHC 241617
AF303 01GGA INVEST HDOB 09 KNHC
1609. 1312N 06233W 00690 0021 049 027 216 216 028 00733 0000000000
1610 1309N 06233W 00463 0001 050 022 238 238 024 00482 0000000100
1610. 1308N 06231W 00396 5001 050 020 244 244 021 00406 0000000100
1611 1307N 06230W 00316 5007 050 022 252 252 025 00320 0000000100
1611. 1306N 06228W 00305 5009 051 026 256 256 027 00307 0000000100
1612 1306N 06226W 00306 5010 050 028 256 256 029 00307 0000000100
1612. 1306N 06225W 00300 5010 048 027 256 228 027 00300 0000000000
1613 1305N 06223W 00306 5011 045 028 252 228 030 00306 0000000000
1613. 1304N 06222W 00310 5012 035 024 246 232 025 00309 0000000000
1614 1303N 06221W 00310 5013 035 026 246 228 027 00308 0000000000
1614. 1301N 06220W 00307 5012 037 027 246 224 027 00305 0000000000
1615 1259N 06219W 00301 5013 038 026 246 224 026 00298 0000000000
1615. 1257N 06218W 00305 5014 039 025 248 216 026 00302 0000000000
1616 1256N 06216W 00305 5014 034 024 246 226 025 00301 0000000000
1616. 1254N 06215W 00305 5014 034 024 246 228 024 00302 0000000000
1617 1252N 06214W 00304 5014 031 022 246 232 023 00300 0000000000
1617. 1251N 06213W 00305 5015 028 020 246 236 020 00300 0000000000
1618 1249N 06212W 00305 5015 028 019 250 234 019 00300 0000000000
1618. 1247N 06211W 00305 5015 029 019 250 236 019 00300 0000000000
1619 1246N 06210W 00305 5016 031 017 248 238 017 00300 0000000000
Member Since: September 8, 2005 Posts: 0 Comments: 3805
395. hurricane23
4:31 PM GMT on August 24, 2006
JP its a combination of both features right now.
Member Since: May 14, 2006 Posts: 8 Comments: 13804
394. WeatherByrd
4:31 PM GMT on August 24, 2006
The storm on the East coast had like 3 minutes to do something before it hits land.
393. littlefish
4:31 PM GMT on August 24, 2006
Dr. M comes on here once-in-awhile to chat. Usually when things are changing or things are heating up regarding tropical systems. He'll have an update on the reconn this afternoon per his earlier update. Looks like 97L has a fat donut hole in the middle where convection should be for a developnig system. Good convection outside that area though...
392. Bamatracker
4:30 PM GMT on August 24, 2006
what is "flight level"? I noticed that they dipped down from an altitude of 19000 to about 3500....so which one would I look at for the 15% decrease?
Member Since: May 17, 2006 Posts: 6 Comments: 1367
391. thelmores
4:30 PM GMT on August 24, 2006
"On that note, I can not believe that I can not get anyone to bite on the area off the E coast...."

i bit, i bit! LOL

I'LL BE WATCHIN! ;)
Member Since: September 8, 2005 Posts: 0 Comments: 3805
390. WeatherByrd
4:30 PM GMT on August 24, 2006
Ok help me out here for just a minute. I'm new. Shear is where the wind direction is defferent from the upper levels and the lower levels?
387. StormJunkie
4:27 PM GMT on August 24, 2006
WB, I work in a manufacturing plant because I do not have the time, money, or education to do what I would like to...lol.

I hope to bring more functionality to the site over this winter, but it will always serve the main purpose of being a portal to great FREE weather info.

Thanks for the props! :)
SJ
Member Since: August 17, 2005 Posts: 26 Comments: 16866
386. Bamatracker
4:27 PM GMT on August 24, 2006
16:09:00 13.23 -62.53 3501 52 36 37 67 64

36 kts at 3501 feet...what does that equal at the surface?
Member Since: May 17, 2006 Posts: 6 Comments: 1367
385. emagirl
4:27 PM GMT on August 24, 2006
hi WeatherByrd
384. Melagoo
4:26 PM GMT on August 24, 2006
The Caribbean going to erupt into Storm making machine now....
Member Since: July 31, 2006 Posts: 19 Comments: 1577
382. littlefish
4:26 PM GMT on August 24, 2006
Kind of a gaping hole opening up near center of 97L. Lots of convection, just nor in the right area...
381. emagirl
4:25 PM GMT on August 24, 2006
well then does that mean it is a TD
380. Tazmanian
4:25 PM GMT on August 24, 2006
we have a TS?
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
379. Bamatracker
4:25 PM GMT on August 24, 2006
it is jp...im looking at it right now and it is changing everytime i reload the page.
Member Since: May 17, 2006 Posts: 6 Comments: 1367
378. StormJunkie
4:25 PM GMT on August 24, 2006
Posted By: StoryOfTheHurricane at 4:18 PM GMT on August 24, 2006.
we might be about to witness a monster


Calm down Story, everyone is fine for now, just keep an eye on it.

On that note, I can not believe that I can not get anyone to bite on the area off the E coast....

Got to get back to work. See ya'll later.

StormJunkie.com-Forecast models, imagery, marine data, wind data, preparedness info, and much more. You can find some of the best free weather data available on the web from here.
Member Since: August 17, 2005 Posts: 26 Comments: 16866
377. hurricane23
4:25 PM GMT on August 24, 2006
Looks to me like shear is really affecting 97L right now.
Member Since: May 14, 2006 Posts: 8 Comments: 13804
376. WeatherByrd
4:25 PM GMT on August 24, 2006
Hi emagirl!
375. thelmores
4:24 PM GMT on August 24, 2006
"Does Jeff Masters ever get on here and chat?"

not really, but he will "break in" sometimes and add or correct some information/ misinformation


Member Since: September 8, 2005 Posts: 0 Comments: 3805
373. WeatherByrd
4:23 PM GMT on August 24, 2006
Does Jeff Masters ever get on here and chat?
372. thelmores
4:23 PM GMT on August 24, 2006
During reconnaissance of tropical system INVEST a maximum wind speed of 41 mph, at 9882 feet, was found by the government plane.

16:07:30 13.36 -62.5 8180 62 41 41 55 41

15 minutes ago....
Member Since: September 8, 2005 Posts: 0 Comments: 3805
371. WeatherByrd
4:22 PM GMT on August 24, 2006
stormjunkie your site is pretty cool. What do you do for a living?
370. emagirl
4:21 PM GMT on August 24, 2006
does anyone know when we will know something from recon?
369. thelmores
4:21 PM GMT on August 24, 2006
goole earth from storm2k
Member Since: September 8, 2005 Posts: 0 Comments: 3805
368. StoryOfTheHurricane
4:21 PM GMT on August 24, 2006
yep, im out to lunch, we'll see action this evening or tonight for sure
367. Bamatracker
4:20 PM GMT on August 24, 2006
is the recon flying there yet...what is the eta for them to reach the system?
Member Since: May 17, 2006 Posts: 6 Comments: 1367

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.