Disturbance 90L close to tropical depression strength; TD 2 may rise again

By: Dr. Jeff Masters , 2:02 PM GMT on August 14, 2009

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A strong tropical wave (90L), with a large circulation and a moderate amount of heavy thunderstorm activity, is a few hundred miles southwest of the Cape Verdes Islands, off the coast of Africa. This morning's QuikSCAT pass shows that 90L has a large circulation, but this circulation is not yet well-formed, as it is elongated along an east-west axis. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are gradually becoming better organized, with some spiral banding evident on the south side of the storm. Satellite intensity estimates from NOAA already put 90L at tropical depression strength with 30 mph winds, but the storm does not yet have a well enough formed circulation to be classified as a depression. 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 was. However, there is some dry air from the SAL being sucked into the circulation of 90L, and this is retarding its development.

Wind shear is moderate, about 10 - 15 knots, but is forecast to fall to the low range, 5 - 10 knots, later today. Shear is then forecast to remain low for the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow 90L to develop into a tropical depression by Saturday, and potentially reach hurricane strength by Wednesday. Most of our reliable models strengthen 90L into a hurricane by Wednesday, when the storm is expected to be near the northern Lesser Antilles Islands. One important outlier is the ECMWF model, which has 90L passing to the north of the islands, and eventually recurving out to sea east of Bermuda. The ECMWF was by far the most reliable model for forecasting hurricane tracks last year. However, all of our models are pretty unreliable going out 5 days in advance for systems that have yet to reach tropical depression strength. Once 90L becomes a tropical depression and develops a well-formed circulation, the models will have a better handle on forecasting where it will go.


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

Tropical Depression Two may come back
Tropical Depression Two died yesterday, but may rise again. Satellite loops of the remnants of the storm show that heavy thunderstorms are again attempting a comeback near the axis of what is now a tropical wave. However, dry air continues to interfere with the development of the thunderstorm activity, and moderately high wind shear of 15 - 20 knots is also inhibiting the process. Wind shear over the remnants of TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next four days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C two days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to the north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that any re-development of the storm will be slow to occur. NHC has given the system a medium (30 - 50% chance) of becoming a tropical depression again by Sunday morning. Only one reliable model, the NOGAPS, is predicting regeneration of TD 2. The NOAA Hurricane Hunters are flying research missions into the remnants of TD 2 today and Saturday.

I'll have an update Saturday morning, or earlier, if significant developments occur.

Jeff Masters

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The blog is acting like the words from the NHC are like the ten commandments.
.
.
Then after they speak, the blog spends the next 6 hours saying how wrong they are.
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5am it is!
I will be shocked if 02L and 90L are not TDs by then.
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I will be back in 15 or so...gotta step away from the computer lol
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting louisianaboy444:
Ladies and Gentleman Mr. Conway Twitty

LOL
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Quoting extreme236:


Nothing.




thats all this Nothing??

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Quoting Weather456:


tropical disturbance?


Those are classified as "DB"
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting AussieStorm:
Wow, 4 area's of interest now.
When did this decide to happen?<
Been like that since at least 11AM GMT, except that 1 was orange then.
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Is anyone else seeing 02L jog a little south of west?
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First Pillage - then Burn
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I'm thinking deffinitely TD2 will have advisories re-iniated...and possibly 90L upgraded to TD3.
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Quoting CaicosRetiredSailor:



well...

at least that looks a bit more hopeful for us in the TCI


Where in TC? I LOVE it there!! My brother used to live there. Was very sad for Ike to hit y'all (and then me).
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Quoting sammywammybamy:




i think the NHC just wants me to Crack ... LOL


Ya they are punishing you for using your middle finger which your momma told you never to do.....LOL
Member Since: September 2, 2007 Posts: 179 Comments: 20448
*Envisions an arguement at the NHC* "How can we classify this little thing without classifying that giant to the east"
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Ladies and Gentleman Mr. Conway Twitty
Member Since: August 29, 2006 Posts: 22 Comments: 1352
DO NHC has a Cane adict free phone?
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Quoting IKE:
***Avila dealt 2 aces*** Mucks hand***



Tropically depressed?


tropical disturbance?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
14/2345 UTC 15.2N 44.9W T1.5/1.5 02L
14/2315 UTC 11.7N 30.8W T1.5/1.5 90L
Quoting extreme236:
They didnt upgrade Dolly until 11:45. Guess we wait for a special discussion now? lol
yup
((( Nole !!!!! ))) Good to see ya!!!
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Some good news from New Orleans Saints won 17-7
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Quoting Tazmanian:



what about for 90L??


Nothing.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
I think Ike has something to do with this DELAY...
to get the 0 - 0 - 0 up til AUG 15TH
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NHC began advisories on TD2 the first time at 6am, an hour after the official advisory.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
3157. Patrap
.."Hmmmmm,those District 9 ALiens have stop pumping that SAL into the Atlantic,..but the 11pm being late,..well..that is disturbing"...



Member Since: July 3, 2005 Posts: 428 Comments: 129844
Quoting extreme236:
AL, 02, 2009081500, , BEST, 0, 145N, 448W, 25, 1007, TD



what about for 90L??
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3155. IKE
***Avila dealt 2 aces*** Mucks hand***

Quoting extreme236:
AL, 02, 2009081500, , BEST, 0, 145N, 448W, 25, 1007, TD


Tropically depressed?
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evening everyone...sounds like a town hall meeting going on in here about either it is or isn't...lol
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WB Aussie! See what happens? Go spend a little time with the son and all heck breaks loose :P
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Quoting cchsweatherman:
Dear lord people. You all (with the exception of a select few) are acting like little kids in a candy store. Calm down and give the NHC some time.


We're just having some fun, that's all.
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hi baja...thanks patrap...board moving so fast hard to keep up...gonna wear out my f5 key as well and still never get to read half of what is written...
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I think that the NHC will issue a special advisory around 2:00 AM EST on one of them, and start on the other at 5:00.
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People, the only reasons it is late is because they are issuing new advisories on TD2 or they did not upgrade it at this time.
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Quoting JRRP:

lol


LOL!!
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The Little Engine That Could:

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They didnt upgrade Dolly until 11:45. Guess we wait for a special discussion now? lol
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting cchsweatherman:
Dear lord people. You all (with the exception of a select few) are acting like little kids in a candy store. Calm down and give the NHC some time.
we havent had this exitement all year
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Join the mob against NHC!!!
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3140. JRRP
Quoting Weather456:
11PM,

9 deaths already reported

lol
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3139. Patrap
Welcome back to the Horde tigger..
Member Since: July 3, 2005 Posts: 428 Comments: 129844
AL, 02, 2009081500, , BEST, 0, 145N, 448W, 25, 1007, TD
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Wow, 4 area's of interest now.
When did this decide to happen?



P.S I know its 3 hours old.
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Quoting Weather456:
11PM,

9 deaths already reported


New WU sport has been created.

Bungle jumping from your ceiling using your neck!
Member Since: June 9, 2007 Posts: 4 Comments: 15950
Sammy you better give us that darn report now....
Member Since: September 2, 2007 Posts: 179 Comments: 20448

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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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