Caribbean disturbance 99L a dangerous rainfall threat for Haiti, Jamaica, and Cuba

By: Dr. Jeff Masters , 4:12 PM GMT on October 20, 2012

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A tropical wave embedded in a large trough of low pressure (Invest 99L) covers a large portion of the Central Caribbean between Hispaniola and the northern coast of South America. This storm has the potential to be a dangerous rainfall threat for Haiti, Jamaica, and eastern Cuba. The disturbance is headed west at less than 5 mph, is over very warm waters of 29°C, and is in a moist environment. 99L has a large area of heavy thunderstorms that are beginning to show some organization, as seen on visible satellite loops. Wind shear is a low 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday. This should allow for some steady development of 99L, and there has been a good deal of model support for 99L becoming a tropical depression by Wednesday. Steering currents favor a continued slow westward movement for 99L through Tuesday, which will bring a multi-day period of heavy rains to Haiti, Jamaica, and eastern Cuba beginning on Sunday. The Dominican Republic may also see some heavy rains, though not as great. On Wednesday, a strong trough of low pressure will approaching the Eastern U.S., and the GFS and ECMWF models predict that this trough will turn 99L to the north, bringing the storm into the southeast Bahama Islands on Thursday or Friday. In their 8 am EDT tropical weather outlook, NHC gave 99L a 30% chance of developing into a tropical cyclone by Monday morning. I put these odds higher, at 40%. An Air Force hurricane hunter aircraft is scheduled to investigate 99L on Sunday afternoon.


Figure 1. Morning satellite image of Invest 99L.

Invest 90L in the middle Atlantic
A tropical wave (Invest 90L) about 1000 miles east-northeast of the northernmost Lesser Antilles Islands is headed west-northwest at about 10 mph. The disturbance has a modest amount of heavy thunderstorms, as seen on visible satellite images, and has gotten tangled up with an upper-level low pressure system. This upper-level low is pumping cool, dry air into the disturbance, which will keep any development slow over the next few days. Wind shear is a high 20 - 25 knots, but is forecast to drop to the moderate range, 10 - 20 knots, Sunday through Monday. This may allow for some slow development of 90L before it encounters very high wind shear of 20 - 40 knots on Tuesday and Wednesday. None of the reliable computer models develop 90L into a tropical cyclone. It's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 20% chance of developing into a tropical cyclone by Monday morning.

Jeff Masters

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Quoting wxchaser97:

There is no 5o'clock or 11o'clock advisory unless there is an active depression, storm, or hurricane. At 8o'clock is the next TWO and update for 99L and 90L.


Thanks I was wondering.
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hr 144

Member Since: July 15, 2006 Posts: 171 Comments: 53827
Well time to use the ignore feature again.
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Whatever happened to the cow that was lifted into the air by the tornado?

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Quoting AZweather13:
Where's the 5o'clock advisory on the NHC website?

There is no 5o'clock or 11o'clock advisory unless there is an active depression, storm, or hurricane. At 8o'clock is the next TWO and update for 99L and 90L.
Member Since: March 16, 2012 Posts: 127 Comments: 7942
How is everyone today?
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Gracias
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What's been happening?.And is the blog finally calm?
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¿Cualquier posibilidad del lío en el título de Caribe a Florida? ¿O más son las Bahamas probables?
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hr 138

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Quoting HurricaneHunterJoe:
¿Es esto el blog español de Huracán?
No, no es.
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Quoting AZweather13:
Where's the 5o'clock advisory on the NHC website?
No 5:00 advisory unless it is a developed system threatening land.
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Quoting HurricaneHunterJoe:
¿Es esto el blog español de Huracán?
no se, parece que si
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Where's the 5o'clock advisory on the NHC website?
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¿Es esto el blog español de Huracán?
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hr 126

Member Since: July 15, 2006 Posts: 171 Comments: 53827
Hola! Que tal?
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Quoting GraduateStudent2012:


Your Spanish needs some fine tuning, Laurie! LOL.

Just kidding, ma'am, =)
Actually it is freetranslation.com
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hr 117

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hr 108

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I just did a detailed tropical Atlantic update. It explains the complex situation with 99-L...90-L...and also ex-Rafael...and more. For those that are still learning....their is a lot of info here that can be digest with words and figures to hopefully learn more. Please feel free as usual to leave comments or questions....
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hr 99
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hr 90

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Quoting GraduateStudent2012:


Tomare su ofrecimiento en cuenLos orificios nasales están en la costa del sudeste tan si pasa esta manera y usted está por los orificios nasales parará desear. ta, senora!
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hr 72

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hr 63

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what you want and what you get
will be two different things
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Can u guys Type the hour in the model runs..tia
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<>img src="
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<>img src="
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<>img src="
Member Since: July 15, 2006 Posts: 171 Comments: 53827
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Quoting GraduateStudent2012:


Pudrete, degenerado; flagged & reported.




hi jfv you been reported to wounder blog admin for bypassing your bannd


evere time you bypass your ban you will get reported and lock back up
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1441114: ...and yes COMPUTERS do lie period , end of STATEMENT !
281 stormwatcherCI: Ok, I am an idiot but you are still here on the computer lol.

Then again, his computer could be lying by claiming to be him when it posts.
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she may even make a run at the gap
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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.