Low Pressure near Northern Leewards

[cycloneye]

Closeup Water Vapor loop



Above is a good closeup of the upper low developing just north of the Leewards and the interaction with the wave occuring to the east of it.

[wxman57]

Sounds reasonable. A 5% chance is less than the average tropical wave during the season. Way too much shear for this to develop, but not enough to 100% rule out development. In my outlook I thought development chances were too low to mention.

Here's my take, based on what I see in water vapor imagery and from the ECM/GFS H25 wind/divergence forecasts over the next couple of days.

There is a well defined H25 shear axis running ENE from the Mona Passage into the central ATLC, separating a strong 50-70KT ENE jet streak (running from 25N60W into eastern Cuba/Hispanola) from a 40-50kt WSW jet streak (strecthing ENE-ward from the northern Leewards). Water Vapor imagery shows an ULL forming in the north and NE of PR/USVI, which should do two things:

1) As H25 winds become more out of the SW and weaken slighly, shear should weaken as a result (from "extremely hostile" to "pretty unfavorable, but not ridiculously prohibitive", if you get my drift).

2) Create an area of strong H25 divergence near and near and to the east/northeast of the LA.

What I expect over the next day or two is for the wave to become even more convectively active, owing to increasing divergence/forced ascent. If there is enough of a convective burst over the wave, there may be enough pressure falls to spin up a weak vortex, given the T-wave in that area was already showing some broad cyclonic turning. However, after any ULL that forms near/north of PR is progged to be weak/transient, and thus H25 winds are forecast to veer around to NW at about 15kt, give or take. Given the wave will be embedded in low level E-ESE flow of at least 10-15kt, that would translate into ~25-30kt of shear.

I'd give it about a 50/50 shot at becoming an invest over the next 2 days, but only about a 5% chance to actually become a TC.

[GCANE]

Cycloneye:

Nice link. I can clearly see the high Theta-E air being pulled out of the ITCZ by the ULL right into the convection. Lifting Indexes of the ITCZ air are moderately unstable at about -6 and there is a lot of moisture with Precip Water at about 2.3 to 2.5. It looks like definite UL Outflow is being generated by the convection.

Here is another link that shows a closeup of the convection. Be sure to hit the View Satellite button.

I don't know if it is too early to tell yet, but there might be a small spin to it.

http://www.tropicalatlantic.com/satelli ... 15&lon=-57

[wxman57]

18z GFS at 156 hours - Which low is it, the one N of PR or the one in the NE Gulf?

The 06Z GFS keeps the vorticity center and weak low stationary just NE of the Caribbean for 2 days then tracks it off to the northeast and out to sea. 00Z GFS did the exact same thing with it, moved it out to sea to the northeast.

Both models developed a low center along the strong cold front in the eastern Gulf late in the weekend and moved that non-tropical low across Florida early next week. That may be what the European is seeing - just a frontal wave in a high-shear environment. The GFS develops the low into a Nor'easter along the Mid Atlantic Coast by next Wednesday/Thursday. Definitely not a tropical system.

[cycloneye]

More closer than this you dont see all the time. Visible image of the NE Caribbean. Some low level convergence going on just east of Guadeloupe.

[GCANE]

Pressure at Guadalope is 1013mb

http://weather.noaa.gov/weather/current/TFFR.html

[hurricanetrack]

wxman57 said "what the European is seeing - just a frontal wave in a high-shear environment"

But the 200mb map at 168 hours shows an anti-cyclone over the NW Caribbean with less than 3 knots right over the surface low. This is the latest run, the 00z. Would this be considered a high shear environment? I am just a little confused since this is exactly what the ECMWF 200mb map shows at 168 hours. I cannot post a link to it b/c I am looking at it on a pay site but I am sure someone can find it and post it here.

Actually, the Euro shows very little shear at 200mb throughout most of its 00z run over the NW Caribbean.

[Ed Mahmoud]

JB says he will be 'simply wrong' if a TC doesn't develop in the Western Caribbean in 5 to 10 days.

[chadtm80]

http://www.ssd.noaa.gov/goes/east/catl/loop-avn.html

[DESTRUCTION5]

JB says he will be 'simply wrong' if a TC doesn't develop in the Western Caribbean in 5 to 10 days.

Ok Ill Bite..What is that supposed to mean?

[Ed Mahmoud]

Means JB is predicting a Caribbean TC in to 10 days.

[wxman57]

JB says he will be 'simply wrong' if a TC doesn't develop in the Western Caribbean in 5 to 10 days.

Yes, he probably will be wrong.

[wxman57]

wxman57 said "what the European is seeing - just a frontal wave in a high-shear environment"

But the 200mb map at 168 hours shows an anti-cyclone over the NW Caribbean with less than 3 knots right over the surface low. This is the latest run, the 00z. Would this be considered a high shear environment? I am just a little confused since this is exactly what the ECMWF 200mb map shows at 168 hours. I cannot post a link to it b/c I am looking at it on a pay site but I am sure someone can find it and post it here.

Actually, the Euro shows very little shear at 200mb throughout most of its 00z run over the NW Caribbean.

What I was attempting to say is that I don't believe a storm will develop in the NW Caribbean (as the European model is indicating), but that the ECMWF may be picking up on energy associated with the strong cold front over the SE Gulf and incorrectly developing a low in the NW Caribbean rather than along the front.

It's still possible to see another storm in the western Caribbean this season, but it's looking less likely every day.

[flwxwatcher]

From Dr Jeff Masters Weather Underground Blog this Morning.

An area of disturbed weather has developed near the northern Lesser Antilles Islands, due to a westward-moving tropical wave interacting with an upper-level low. Wind shear is currently too high (30 knots) to allow development of this disturbance. However, the past two runs of the NOGAPS model have predicted that wind shear will fall enough by Friday to allow a tropical depression to form near the western Bahamas. This storm is predicted to move westward across eastern Cuba and into the Western Caribbean. The GFS model does not go along with this scenario, but hints at a weak system developing and moving northeast out sea over the middle Atlantic. The UKMET and ECMWF models do not develop a Bahamas storm, either, but do show a large region of low pressure with low wind shear developing over the Western Caribbean later this week. It would not be a surprise to see a tropical depression develop in the Western Caribbean late this week or early next week.

http://www.wunderground.com/blog/JeffMa ... amp=200710

[Sanibel]

The models are failing to read shear negativity lately.

[cycloneye]

ABNT20 KNHC 231511
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1130 AM EDT TUE OCT 23 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A LARGE AREA OF DISTURBED WEATHER EXTENDING FROM THE LESSER ANTILLES
EASTWARD INTO THE ATLANTIC FOR SEVERAL HUNDRED MILES IS
ASSOCIATED WITH A WESTWARD-MOVING TROPICAL WAVE AND AN UPPER-LEVEL
TROUGH. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR TROPICAL CYCLONE
FORMATION.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$

FORECASTER AVILA
WWWW

[hurricanetrack]

wxman57 said "what the European is seeing - just a frontal wave in a high-shear environment"

But the 200mb map at 168 hours shows an anti-cyclone over the NW Caribbean with less than 3 knots right over the surface low. This is the latest run, the 00z. Would this be considered a high shear environment? I am just a little confused since this is exactly what the ECMWF 200mb map shows at 168 hours. I cannot post a link to it b/c I am looking at it on a pay site but I am sure someone can find it and post it here.

Actually, the Euro shows very little shear at 200mb throughout most of its 00z run over the NW Caribbean.

What I was attempting to say is that I don't believe a storm will develop in the NW Caribbean (as the European model is indicating), but that the ECMWF may be picking up on energy associated with the strong cold front over the SE Gulf and incorrectly developing a low in the NW Caribbean rather than along the front.

It's still possible to see another storm in the western Caribbean this season, but it's looking less likely every day.

I don't know, this one looks pretty "real" so to speak. Best shot in a while perhaps. At least the ECMWF shows favorable conditions aloft if that were the only model to watch- of course, it is not, but still, less than 3 knots of shear is looking good for development. It would be nice to get a weak hurricane in to the SE with all its moisutre and such.

[cycloneye]

23 of October 12z GFS 200mb at 78 hours Upper winds are light in Western Caribbean at 78 hours.

23 of October 12z GFS 200mb at 90 hours

23 of October 12z GFS 200mb at 108 hours Continued light upper winds in Western Caribbean.

23 of October 12z GFS 200mb at 120 hours More light upper winds in Western Caribbean.

23 of Octo9ber 12z GFS 200mb at 144 hours Shear increases to 20kts in parts of Western Caribbean.

23 of October 12z GFS 200mb at 174 hours Light upper winds in Western Caribbean.GFS dosent have anything in 174 hours in Western Caribbean despite the light upper winds in the period.I will stop here.

[GCANE]

Shear continues to drop NE of the LE Islands and is running around 20 knots.

http://cimss.ssec.wisc.edu/tropic/real- ... g8sht.html



Organization doesn't look too bad.





UL Winds are running about 15 knots over the convection:



Still maintaining a good feed of high Theta-E air from the ITCZ.

All in all, this may have a chance.

[cycloneye]

23 of October 12z CMC

The pro mets rank CMC as not credible for the deep tropics so I am only posting this 12z run for pure entretainment. Imagine a hurricane moving thru Puerto Rico and Hispañola and gets stronger after it moves thru the 12,000 feet mountains.