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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Quoting TampaSpin:


Its going south again watch....



lol had a nice little bounce back in the last hour though
Member Since: August 2, 2007 Posts: 19 Comments: 19234
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Quoting bajelayman2:
WHY DID U DO THAT!?!?!?
Quoting CaneHunter031472:
How is the ULL over the Caribean going to affect the trajectory of the Potential TD2 and TD3?


the upper low weakens or head west within 126 hrs, well ahead of both disturbances but may help influence TD 2 to some degree by pulling it north. Ernesto 2006 was pulled north by an upper low, also a storm in 2004, but cannot recall.
Member Since: Posts: Comments:
3380. Patrap
RAAMB
Currently Active Tropical Cyclones



Member Since: July 3, 2005 Posts: 426 Comments: 128632
Avila's playing poker and the advisory wont be out till 2am :P
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Quoting extreme236:
Whatever happened to that one guy from last year who seemed to have inside sources from the NHC on the advisory info? Sure could use him now...


I think he posts some, but not as much as last year.
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Quoting extreme236:
90L starting to look more like a tropical storm.



yup
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Quoting extreme236:
90L starting to look more like a tropical storm.
yup
Quoting Patrap:
Nothing Lamer than partisanship here..

I dont see Tampaspin posting those stock #'s as he used to..

Wink,Wink,,,



Its going south again watch....

Member Since: September 2, 2007 Posts: 178 Comments: 20443
Whatever happened to that one guy from last year who seemed to have inside sources from the NHC on the advisory info? Sure could use him now...
Member Since: August 2, 2007 Posts: 19 Comments: 19234
TWC is going to use this song as their theme for these storms:

Link
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I guess the latest model run id answering my qestion. Not good at all....
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What a come back by the Sox! Where is the 11pm advise?
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I didn't F5 that either :P
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LOL......Inital out for the new GFS ... *guzzles coffee* LMAO!!!
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Ok I'm sorry but that's a TD at least. It looks 100 times better than it did earlier today
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Quoting canesrule1:
At the moment I prefer the Gulf, honestly.

That said, anywhere from Gulf to East Coast states are still open.

Either way, some of the islands are shortly going to get hit.

I am on one.

Not funny.
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90L starting to look more like a tropical storm.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
How is the ULL over the Caribean going to affect the trajectory of the Potential TD2 and TD3?
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Quoting RufusBaker:
Who on here thinks that FL is really in the bullseye with 90?>


And any south Florida hit puts the storm in the gulf for a round 2 hit
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Thats how Dean and Georges evolved, lopsided convection became more symmetric. This is so similar to those 2 storms, that its hard to ignore the models

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Quoting RufusBaker:
Who on here thinks that FL is really in the bullseye with 90?>

90L? Doubtful. 02L? Maybe.
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Quoting extreme236:


Link
thanks
Something to consider... probably should check our Hurricane Rations!
Quoting CandiBarr:


hubby says the DC in robert, la is getting updates from bentonville already on this one.
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14.357 N 46.008 w Wind Direction NW ( 320 deg true )15.5 kts
29.78 in
Pressure(PTDY): -0.07 in ( Falling )
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My plot puts exTD2 1000 miles due East of Martinique. At current rate of movement if it continued traveling West, that is just over 60 hours.

CRS
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ok...i'm out...nothing gonna be said till morning and board moving too fast anyway with mostly jokes...can't pull any info outta here tonight...lol...nite!
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Quoting jazzygal:


No!! It's Friday, they went home early. Good call on TD 2 this morning.


Thanks.
Member Since: September 2, 2007 Posts: 178 Comments: 20443
Quoting RufusBaker:
Who on here thinks that FL is really in the bullseye with 90?>


Perhaps a few modelers are thinking such a thing.

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3350. hahaguy
Ok , It will be here in the morning so I'll wait till then.
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3349. Patrap
Nothing Lamer than partisanship here..

I dont see Tampaspin posting those stock #'s as he used to..

Wink,Wink,,,

Member Since: July 3, 2005 Posts: 426 Comments: 128632
3348. KEEPEROFTHEGATE (Mod)
2009 Storms
Active Year


Atlantic
91L.INVEST
90L.INVEST
02L.TWO

East Pacific
10E.GUILLERMO
09E.NINE

Central Pacific

West Pacific
94W.INVEST
91W.INVEST
01C.MAKA

Indian Ocean

Southern Hemisphere
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Quoting RufusBaker:
Who on here thinks that FL is really in the bullseye with 90?>
me
#3328 security cert. issues...
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there is an old saying no news is good news but i differ tonight. no news is bad news. expect advisories on both systems
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Are we waiting for the tropical outlook or what? o.O
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Quoting Beachfoxx:
Has Walmart run out of SPAM yet???


hubby says the DC in robert, la is getting updates from bentonville already on this one.
Quoting TampaSpin:
I know its Obama's fault ......he cancelled funding for NHC just before the update......LMAO


No!! It's Friday, they went home early. Good call on TD 2 this morning.
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3341. Patrap

.."I gotta tell ya folks,the Crowd is turning ugly here...

..They just go to Al Roker and well,its not a pretty sight"..,back to you guy's in the Studio"..




Member Since: July 3, 2005 Posts: 426 Comments: 128632
Quoting TampaSpin:
I know its Obama's fault ......he cancelled funding for NHC just before the update......LMAO
Yeah they ran out of money for the cash for clunkers program again!
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Quoting WeatherStudent:



Really? How were you actually able to tell?


He didn't make it all doom and gloom. In fact, he didn't even tell me to tune in to the next newcast or else.
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Who needs the NHC?!?!? We have JFVWS in da house!!!!!!!!!!!!1
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Quoting Patrap:


TD 2, maybe now Ana seems to have decided to make a beeline for us in Barbados.

Tomorrow is going to be insane at the markets if its declared a storm tonight.
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Quoting canesrule1:
can u post ur "illegal" site again, thanks!


Link
Member Since: August 2, 2007 Posts: 19 Comments: 19234
As snaggle pus would she both systems are exiting stage left headed wsw I presume.
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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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