New tropical depression could form off the coast of Africa

By: Dr. Jeff Masters , 1:12 PM GMT on September 25, 2009

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A tropical wave (99L) is located near 15N, 30W, about 300 miles west of the Cape Verdes Islands. This wave has seen an increase in heavy thunderstorm activity this morning, and low-level spiral bands have formed. The system can already be classified as a tropical depression using the satellite-based Dvorak technique. This morning's QuickSCAT pass showed a loose but closed circulation, with top winds of 30 mph in the heaviest thunderstorms. Wind shear is moderate, about 10 - 20 knots. There is a modest amount of dry air to 99L's west that does not appear to be interfering with the storm's organization.


Figure 1. Morning visible satellite image of Invest 99L (left side of image) and a new tropical wave moving off the coast of Africa.

As 99L moves west-northwest over the next two days, sea surface temperatures will cool by 1°C and winds shear will remain in the moderate range. Some dry air may also affect the storm. These conditions give 99L a good chance of forming into a tropical depression, and NHC has given the system a moderate (30 - 50%) chance of developing into a tropical depression by Sunday. By Monday, wind shear will increase to the high range, 20 - 30 knots, and 99L will probably weaken or be torn apart. None of the computer models forecast development of 99L or any other system in the Atlantic over the next seven days.

A new tropical wave with plenty of heavy thunderstorm activity and some spin is moving off the coast of Africa today. This wave is under a moderate amount of wind shear, 10 - 20 knots, and has some potential for development this week as it moves west or west-northwest past the Cape Verdes Islands.

The latest wind shear forecasts from our major computer models show high values of wind shear affecting most of the tropical Atlantic for the next ten days. This is typical for an El Niño year, and it will be difficult for any storms to get to hurricane strength over the next ten days because of the high shear. The latest 16-day GFS forecast predicts wind shear will decline some by the 2nd week of October, though.


Figure 2. Wind shear forecast for Thursday, October 2 at 00 UTC made by last night's 00Z run of the GFS model. Wind shear is expected to be high over most of the tropical Atlantic for the next ten days, including the Caribbean. Wind shear values below 8 m/s (about 15 knots, red colors), are typically needed to support tropical storm formation.

Jeff Masters

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Quoting iceman55:
hunkerdown You don't even know me..get life
nor do I know most of the children that live in my neighborhood, so whats your point ?
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Quoting btwntx08:
hi all i see hunkerdown bossing around iceman


I don't think what Hunkerdown was asking is unreasonable. Crediting the source with an image is typically preferred, thus preventing the ever-popular copying text from the TWO and claiming as one's original opinion.
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Quoting iceman55:
hunkerdown need tell truth.STFU already
enjoy your ban !
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Quoting pearlandaggie:
549. trust me...i've been banned for criticizing the poor grammar of those worse than my 3rd grader! lol
now thats the truth...at this point being banned means nothing here as people like that have caused this blog to become a joke for the most part. as I am sure you have noticed, most of the "regulars" are rarely here anymore.
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Quoting btwntx08:
hi all i see hunkerdown bossing around iceman i fully expect u to apologize to iceman as u never say that to someone like that...iceman is trying wants he wants ur not the boss of him.
apologize for what, that truth...
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549. trust me...i've been banned for criticizing the poor grammar of those worse than my 3rd grader! lol
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Quoting hunkerdown:
we all see you are good at copying and pasting others words and work...can you apeak legibly on your own ?


TAZ ?? regarding an earlier post ... good night all ... good eve ...
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Quoting iceman55:
lolpearlandaggie
if you only understood...
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is it still "speak like a pirate" day?
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535. watch it...that kind of comment will get you banned for criticizing the sacred cow! lol
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Quoting iceman55:
hunkerdown we all see you are good at copying and pasting others words and work...can you apeak legibly on your own ?s-p-e-a-k e-n-g-l-i-s-h


Are you playing the "I know you are, so what am I" game?
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Quoting iceman55:







Using the AMSU-derived azimuthally averaged temperature and height files radial/height cross sections of temperature and tangential wind are created (see Demuth et al (2004) ). The tangential wind field is derived using the 2-d gradient wind equations. Note that the resolution horizontal of the AMSU instrument results in a smooth temperature field and an unrealistically low tangential wind speeds. These images are useful in determining the thermal structure of the tropical cyclone.
since you keep osting this over and over, please explain...in YOUR own words...
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Quoting TampaSpin:
A poor job of the models forming a TD or was it a poor job of NHC upgrading it to a TD?


Still hard to believe they don't ask your opinion first isn't it, the nerve of them.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting iceman55:
hunkerdown s-p-e-a-k e-n-g-l-i-s-h
we all see you are good at copying and pasting others words and work...can you apeak legibly on your own ?
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A poor job of the models forming a TD or was it a poor job of NHC upgrading it to a TD?
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Quoting pearlandaggie:
orca, are you cold yet?

what's the temp like up there?




Only because its dark :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting PcolaDan:
On History channel right now (10:00 central) That's Impossible: Weather Warfare

Using tornados, hurricanes and other natural phenomenon as weapons of war.


Well, that was a conspiracy theorists dream.
Member Since: August 22, 2008 Posts: 12 Comments: 6010
Quoting iceman55:
hunkerdown comeing said to my face.
s-p-e-a-k e-n-g-l-i-s-h...your posts make Taz's look like perfect grammer
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TD#8 has about 24hrs left of trying to become Grace.....After that, TD8 will get hit with major Shear as it continues to the NW! Little chance it will survive past 72hrs.
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evenin folks

frankly did not expect to see a thing, let alone a depression, in the atl. today.

seems to be a Cabo Verde season, this one
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Quoting hunkerdown:
actually, you didnt. no different than what WS did. Almost all your meaningful posts are just images from websites which are all fine and dandy, but odd how you never say why you are posting or give YOUR interpretation. Other tahn that, most of your posts are jibberish or greetings to other bloggers...
and I use the term meaningful with a grain of salt. to just post an image to make your self look knowledgable is not meaningful at all, actually just annoying.
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Quoting iceman55:
SQUAWK i did .
actually, you didnt. no different than what WS did. Almost all your meaningful posts are just images from websites which are all fine and dandy, but odd how you never say why you are posting or give YOUR interpretation. Other tahn that, most of your posts are jibberish or greetings to other bloggers...
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orca, are you cold yet?

what's the temp like up there?
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Quoting foggymyst:
Orca, still looking west..


From you... yes.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Orca, still looking west..
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AOI

AOI

AOI

AOI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Iceman, where and how do you see td # 8 starting to move westward?
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space weather update...

Things have been fairly quiet since the C2.0 solar flare from Thursday evening. Sunspot 1026 has for the most part vanished and Sunspot 1027 which remains a BETA sunspot group, is starting to wind itself down as well.

When will the next Cycle 24 sunspot appear? Let us hope that we do not have to wait very long and that the new Cycle will finally ramp up in activity.


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The model that starts to loop td # 8 looks interesting
Quoting iceman55:



oh wow


The green model that starts to loop td# 8 looks interesting
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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.

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