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 RufusBaker:
I have the phone number to the NHC anybody wanna call???
me
Local met just on. Tropical wave passing by here will be in GOM by Sunday. Pretty much poopooed xTD2, excited by 90L...
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ROFL @ December 1, 2009!!!
Member Since: September 25, 2007 Posts: 53 Comments: 8533
Wow, this was the best/funniest blog secession in a long time. No drama or arguments, just good ole comedy.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
3208. presslord 3:10 AM GMT on August 15, 2009
Where the heck is JFVWS?!?!?!?!


for real...all this excitement and he;s missing this? shirly he's not on a date.....
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3227. IKE
Quoting presslord:
Where the heck is JFVWS?!?!?!?!


Putting up shutters.
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I've been lurking this season.. not much discussion.. but thanks for keeping me entertained tonight!
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If we're going to be here until 5am.

I am going to open a "drinks" stand right next to the pitchfork/torch guy.

CRS
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Quoting DrakoenG:
Ike do you play TEXAS HOLD EM?


This is a weather blog not a poker discussion..take that somewhere else.
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3223. IKE
NHC probably designates first named storm of the Atlantic season on December 1st, 2009.

456 WU bloggers are in the mental ward from pressing F5 key for 6 months, hoping, against hope.

Quoting DrakoenG:
Ike do you play TEXAS HOLD EM?


Watch it on ESPN.
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I have the phone number to the NHC anybody wanna call???
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3220. JRRP
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3219. hahaguy
Quoting presslord:
Where the heck is JFVWS?!?!?!?!


Probably seeing a man about a horse.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
Quoting dcoaster:
Is anyone else seeing 02L jog a little south of west?


Looks so to me. These are both coming through the islands, keeping lower than forecast by the models, is my thought.

We will see, unfortunately.
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I think we are going to break the post record in this blog 3200 post and counting.
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Quoting HurricaneKyle:
I think the NHC will issue a special advisory. They ran the models on a TD.


Or they may be waiting to see if the convection can sustain itself overnight with both systems. Ex-TD2 has had a problem of flaring up and then losing a lot of the thunderstorm activity... they may just be waiting to make sure it (the thunderstorms) are sustained.

We shall see. Just a thought.
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I've been great Nole! Working too much but good. How bout yourself? (I'm thinkin' bump...big bump maybe this way....lol!!)
Member Since: September 25, 2007 Posts: 53 Comments: 8533
Alright I insist that Anna be td2 after all she is smaller and much more feisty only a woman could put up with all crap that has been thrown at her. I hope this does not cause a controversy. But also women go first and she was.
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3206 - Hey Oz!

LOL
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3210. jipmg
Quoting canesrule1:
agreed, maybe around two am, im gonna be on till its a TD!!!! who is with me????


I am.. my eyes are starting to hurt though lol
LMA patrap. You owe me a beer if "impressive" is in the TWO
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Where the heck is JFVWS?!?!?!?!
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Quoting txalwaysprepared:


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).



I live in Long Bay Hills Providenciales, since 1985 (when Hurricane Kate visited).

CRS
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Quoting HurricaneKyle:
I think the NHC will issue a special advisory. They ran the models on a TD.
agreed, maybe around two am, im gonna be on till its a TD!!!! who is with me????
OW! Charlie horse
Member Since: August 29, 2006 Posts: 22 Comments: 1352
3201. Patrap
..."Ike ,I need that Update now..Those Bloggers are closing in fast to port"..



Member Since: July 3, 2005 Posts: 428 Comments: 129792
TWC put it out in big deal fashion NHC would be upgrading at 11 maybe they are on pee break
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Quoting DrakoenG:
WHO would muck a hand when they're dealt POCKET ACES???!??!!???


When did this become PokerStars?
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It must be the Gulf causing delay
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I think the NHC will issue a special advisory. They ran the models on a TD.
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sammy needs one of those little antique birds that use to sit on a water glass and bob up and down drinking the water sitting on his f5 key
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Why is everyone saying 5am just because its late lol
Member Since: August 29, 2006 Posts: 22 Comments: 1352
sammy they might be re writing it to include a warning for your keyboard haha
hey there Baja...how you been??
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I think NHC is waiting for 00z models runs before upgrade anything and make the CONE of unsertany.
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Atlantic Graphical Tropical Weather Outlook:

This product is updated at approximately 2 AM, 8 AM, 2 PM, and 8 PM EDT from June 1 to November 30. Special outlooks may be issued as conditions warrant.
Place your mouse cursor over areas of interest for more information
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Quoting sammywammybamy:
WOW ... IVE BEEN PRESSING THE F5 KEY FOR AN EASY 20 MINUTES..

DANG IT
take a break please, drink a nice glass of Dom Perinon and relax.....
3187. RevInFL
Ok still have a fund going to replace sammy's finger with a robotic super speed model.
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Quoting sammywammybamy:
WOW ... IVE BEEN PRESSING THE F5 KEY FOR AN EASY 20 MINUTES..

DANG IT


give up now, before you damage your keyboard or fingers. Have a nice sleep and it should be there 5am.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
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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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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