TD 2 nearly dead; African disturbance 90L gathering strength

By: Dr. Jeff Masters , 2:38 PM GMT on August 13, 2009

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Tropical Depression Two is near death, but is still worth watching. The dry, Saharan air to the north and west of the depression, combined with moderately high levels of wind shear of 15 - 20 knots, have almost completely destroyed all of TD 2's heavy thunderstorms. Satellite loops of the storm show a well-formed circulation, but almost no heavy thunderstorm activity.

Wind shear over TD 2 is expected to remain in the modereate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C three days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly, and some of the models indicate the TD 2 may get destroyed in the next day or two. However, several models still predict TD 2 will become a tropical storm. The HWRF model predicts TD 2 will become a hurricane five days from now, but this seems unlikely given the dry air and relatively high wind shear affecting the storm.


Figure 1. Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).

African tropical wave 90L
A strong tropical wave with a large circulation and plenty of heavy thunderstorm activity is a few hundred miles south of the Cape Verdes Islands, off the coast of Africa. NHC dubbed this disturbance 90L this morning. This morning's QuikSCAT pass shows that 90L has a very large circulation, and top winds of about 30 mph. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are in two major bands, to the north and to the south of the center. There is no heavy thunderstorm activity near the center yet, and this would have to happen before 90L can be named Tropical Depression Three. Water vapor imagery shows that since 90L is forming several hundred miles south of the dry air of the Saharan Air Layer (SAL), the storm should not be affected by dry air and dust as much as Tropical Depression Two has been. Wind shear is about 20 knots over 90L, and is forecast to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days, which are high enough above the 26°C threshold for tropical cyclone formation to allow some slow development to occur. The GFS and ECMWF models continue to predict the development of this wave, though they are now less aggressive about intensifying it than they were in earlier runs. The consensus among the reliable HWRF, GFDL, GFS, and ECMWF models is to bring 90L to point near or just north of the northernmost Lesser Antilles Islands 6 - 8 days from now. The storm could be at hurricane strength by then, as forecast by the SHIPS intensity model.

I'll have an update Friday morning.

Jeff Masters

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Quoting cg2916:
TD2 has gained 2 degrees north in six hours. I got this from the ATCF database. It's bginning to recurve.


recurve???

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Yeah, changed jobs and moved, getting settled in, so I guess I really haven't had time to sit still. Getting better though. Finally getting settled in.

Quoting hahaguy:


Hey , haven't seen you around lately.
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Quoting popartpete:
I think that it is a spot located in the western Caribbean where a lot of Major Hurricanes pass through. I've heard of it before. If my memory suits me, it is near the area where Hurricane Wilma formed. Now mind you, I am not an expert meteorologist, I'm a journalist, and I work in the Office of Emergency Management in my town. Just a fan of tropical weather, learned in some ways, ignorant in others (for instance I thought TD 2 was going to develop strong, and it did not). I'm addicted to the tropics as some are addicted to gambling, or some other vice. I suppose it could be worse!!!

Link to Hebert Box Info Just do a little fact checking.
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TD2 in the EAtl
Loop
If you look at the loop, convection increasing toward the SE.
Member Since: July 11, 2006 Posts: 14 Comments: 11328
Thaale, wondering that myself.
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1031. slavp
Quoting cg2916:
TD2 has gained 2 degrees north in six hours. I got this from the ATCF database. It's bginning to recurve.
Didn't know it already curved at least once lol
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Quoting TightLines305:



And she can see 90L from her house........Sorry
That is absolutely hilarious!!!
Member Since: July 10, 2007 Posts: 0 Comments: 429

Guillermo now in the EPac
Member Since: July 11, 2006 Posts: 14 Comments: 11328
1027. hahaguy
Quoting charlottefl:
Well 5 years ago today I was sitting in Port Charlotte, the eyewall of Charley making it's way up Charlotte Harbor directly towards us. Ah... good times ;)


Hey , haven't seen you around lately.
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Quoting charlottefl:
Well 5 years ago today I was sitting in Port Charlotte, the eyewall of Charley making it's way up Charlotte Harbor directly towards us. Ah... good times ;)


I will be visiting friends in that area this weekend! They have now just gotten everything back in order.
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1025. cg2916
TD2 has gained 2 degrees north in six hours. I got this from the ATCF database. It's bginning to recurve.
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1024. Thaale
If 90L is developing more quickly than some of the models had forecast, once that development is fed into later model runs would they be likely to trend further north?
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Well 5 years ago today I was sitting in Port Charlotte, the eyewall of Charley making it's way up Charlotte Harbor directly towards us. Ah... good times ;)
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Quoting Joshfsu123:



Sure, if you believe computer models two weeks out. I personally do not and never have. Lots can and will change. We probably will have to wait till next week before we have a better handle of the situation.
Absolutely agree. Long range models have trouble with synoptic scale, longwave pattern evolution, so the smaller scale features pose an even bigger challenge for them. It's def. a crystal ball and should be taken as such.
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TD2 looks like a pimple on an Elephants rump compared to 90L
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting popartpete:
I think that it is a spot located in the western Caribbean where a lot of Major Hurricanes pass through. I've heard of it before. If my memory suits me, it is near the area where Hurricane Wilma formed. Now mind you, I am not an expert meteorologist, I'm a journalist, and I work in the Office of Emergency Management in my town. Just a fan of tropical weather, learned in some ways, ignorant in others (for instance I thought TD 2 was going to develop strong, and it did not). I'm addicted to the tropics as some are addicted to gambling, or some other vice. I suppose it could be worse!!!


There's also another box located around NE Cuba. There's 2 boxes.
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Here are Tropical Updates from STormW and Myself if anyone would like to view!
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting NOLaHSE:
What is the "Herbert Box"?

Thanks.
I think that it is a spot located in the western Caribbean where a lot of Major Hurricanes pass through. I've heard of it before. If my memory suits me, it is near the area where Hurricane Wilma formed. Now mind you, I am not an expert meteorologist, I'm a journalist, and I work in the Office of Emergency Management in my town. Just a fan of tropical weather, learned in some ways, ignorant in others (for instance I thought TD 2 was going to develop strong, and it did not). I'm addicted to the tropics as some are addicted to gambling, or some other vice. I suppose it could be worse!!!
Member Since: July 10, 2007 Posts: 0 Comments: 429
What's this I hear about Lefty420 and STORMTOP returning? You here Lefty?? I resolved to lurking on here after TD10/Katrina, it became more of a political blog than weather for a while, looks like there are a bunch of informative posters on here, some new, some better, some just as crazy and funny as stormtop. Keep up the good work guys this is still by far the BEST place on the internet to discuss the tropics.
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Why is it that Hurricanes in the Atlantic don't look like Typhoons in the Pacific? With all this "it looks like a WPac storm" and all
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Quoting Weather456:


yea. but I didnt think he meant you. Just that some are focusing on the US East Coast.


Some models do show the storms missing the islands and the east coast. I hope those are right.
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1013. Skyepony (Mod)


02L has been puffing off just enough convection to live. Sometimes these become monsters down the road. Also trying to establish a tap on 90L.

Still leary of that wave now around 70W. North of Hispanolia an anticyclone with good upper vortity is maybe 2W more to the west of where the convection is currently building. Lower vorticity began to build in the last 3 hrs. Convergance & divergance are about even & increasing. Shear is falling in the area but currently hampering it somewhat. Looks like it maybe feeding on some daytime heating from the islands.
Member Since: August 10, 2005 Posts: 163 Comments: 37852
Quoting CaneWarning:


Not true. I've been concerned for 456 and have said so many times.


yea. but I didnt think he meant you. Just that some are focusing on the US East Coast.
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Quoting slavp:
He went to typing class


I think his sister would type some of his post because some would make perfect sense but others...
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90L has good bands on its west side, but the east and northeast sides are lacking any outflow and convection. Once it clears the Cape Verde Islands it will wrap up as its circulation gets away from the African coast.
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Quoting canesrule1:
Very unimpressive satellite presentation might cost her being TD status by Friday.



Unimpressive in terms of deep convection centralized over a circulation center but improving overall structure. Might take a little while for it to tighten because its so broad.
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Quoting hurristat:


er... do you mean the east?

you are absolutely correct ..
west side TD2 = east side 90l
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I believe it will be quick to go from TD to TS once it does develop. Also the Bahama's disturbance looks interesting to say the least. Need convection to be persistent before anything can become of it.
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Quoting BenBIogger:


possibly.




Sure, if you believe computer models two weeks out. I personally do not and never have. Lots can and will change. We probably will have to wait till next week before we have a better handle of the situation.
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1005. WxLogic
Quoting Drakoen:
Euro 12z puts it no where near the east coast


It is being consistent with its 00Z run.
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Quoting philliesrock:

That's all people care about...basically it's a fish if it recurves east of the east coast. The 12z Euro significantly impacts the northern islands and Bermuda.


Not true. I've been concerned for 456 and have said so many times.
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Very unimpressive satellite presentation might cost her being TD status by Friday.

1002. Drakoen
Quoting philliesrock:

That's all people care about...basically it's a fish if it recurves east of the east coast. The 12z Euro significantly impacts the northern islands and Bermuda.


That is correct. Most people are more concerned with where they live. We see many storms in the West Pac that impact land but it doesn't phase us in any way.
Member Since: October 28, 2006 Posts: 57 Comments: 30491
Quoting philliesrock:

That's all people care about...basically it's a fish if it recurves east of the east coast. The 12z Euro significantly impacts the northern islands and Bermuda.


thank you
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Quoting canesrule1:
Looks like S-FLA is in for a soaker on Saturday.



Yeah definitly not needed or wanted
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Quoting hahaguy:


90L
Thank you
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Quoting Greyelf:
Maybe it's time to play "Take a drink whenever you see the word Hebert/Herbert". As a bonus - take 2 drinks for every post asking what it is.


Hebert? Please explain the Hebert Box to me.

(j/k)
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996. slavp
Quoting scott1968:
Your neighborhood lurker here...what happened to WS? That dude made me laugh.
He went to typing class
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Quoting TampaMishy:
I'm getting confused now....Which one 90L or TD2?


Possibly both...but just then I was talking about 90L.
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Quoting Weather456:
fih to who? the US?

That's all people care about...basically it's a fish if it recurves east of the east coast. The 12z Euro significantly impacts the northern islands and Bermuda.
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I have 90L developing TD3 within the next 24-36hrs and a Storm shortly there after within a day of becoming a TD.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Maybe it's time to play "Take a drink whenever you see the word Hebert/Herbert". As a bonus - take 2 drinks for every post asking what it is.
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Atlantic Tropical Weather Outlook
--------------------------------------------------------------------------------


000
ABNT20 KNHC 131732
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU AUG 13 2009

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
DEPRESSION TWO...LOCATED ABOUT 885 MILES WEST OF THE SOUTHERNMOST
CAPE VERDE ISLANDS.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE BROAD LOW PRESSURE
AREA AND TROPICAL WAVE CENTERED ABOUT 250 MILES SOUTH OF THE CAPE
VERDE ISLANDS ARE SLOWLY BECOMING BETTER ORGANIZED. A TROPICAL
DEPRESSION COULD FORM FROM THIS SYSTEM DURING THE NEXT COUPLE OF
DAYS AS IT MOVES WESTWARD AT 10 TO 15 MPH. THERE IS A HIGH
CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY EXTENDING FROM THE EASTERN CARIBBEAN SEA ACROSS
HISPANIOLA TO THE TURKS AND CAICOS ISLANDS ARE ASSOCIATED WITH A
WESTWARD-MOVING TROPICAL WAVE. THERE ARE NO SIGNS OF ORGANIZATION
AND UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE FOR SIGNIFICANT
DEVELOPMENT. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

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

$$
FORECASTER BEVEN




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The SHIPS 18z takes 90L up to 98knots
Member Since: October 28, 2006 Posts: 57 Comments: 30491
Quoting TampaMishy:
I'm getting confused now....Which one 90L or TD2?


90L
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Your neighborhood lurker here...what happened to WS? That dude made me laugh.
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Quoting CaneWarning:


Could be. Let's hope.
I'm getting confused now....Which one 90L or TD2?
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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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