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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3834. Drakoen
Quoting weatherboykris:


Link?


Link
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I think we are going to have to start watching the wave right under our noses more closely. It is moving over bathwater and Gulf systems can bomb out quickly, even near land, as we saw with Humberto and Claudette. Shear doesn't look optimal for development but this could get real interesting real quick.
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Quoting Drakoen:
UKMET 00z has shifted to the north with 90L


Link?
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3831. 7544
Quoting jipmg:
alright so at what time can we expect the satellite to be back up


around 315 am est then you get see the big red blobs lol
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3830. Drakoen
Quoting sfla82:


GOOD!!!! Keeps S.Fla away from the bullseye!


No it doesn't
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3829. sfla82
Quoting Drakoen:
UKMET 00z has shifted to the north with 90L


GOOD!!!! Keeps S.Fla away from the bullseye!
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3828. Drakoen
90L UKMET

TROPICAL STORM DEVELOPED IN THE MODEL ANALYSIS AT POSITION :
12.5N 29.6W

VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 15.08.2009 12.5N 29.6W WEAK
12UTC 15.08.2009 11.4N 33.2W WEAK LITTLE CHANGE
00UTC 16.08.2009 11.3N 35.8W WEAK LITTLE CHANGE
12UTC 16.08.2009 11.5N 39.2W MODERATE INTENSIFYING SLIGHTLY
00UTC 17.08.2009 12.6N 42.4W MODERATE INTENSIFYING SLIGHTLY
12UTC 17.08.2009 13.1N 46.3W MODERATE INTENSIFYING SLIGHTLY
00UTC 18.08.2009 14.8N 49.2W MODERATE LITTLE CHANGE
12UTC 18.08.2009 15.6N 53.0W MODERATE LITTLE CHANGE
00UTC 19.08.2009 16.3N 55.9W STRONG INTENSIFYING SLIGHTLY
12UTC 19.08.2009 17.1N 58.8W MODERATE LITTLE CHANGE
00UTC 20.08.2009 17.8N 61.5W STRONG INTENSIFYING SLIGHTLY
12UTC 20.08.2009 18.4N 64.4W STRONG INTENSIFYING SLIGHTLY
00UTC 21.08.2009 19.3N 67.6W STRONG LITTLE CHANGE
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was there a 2am update?
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3826. jipmg
alright so at what time can we expect the satellite to be back up
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3824. Drakoen
UKMET 00z has shifted to the north with 90L
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3823. Patrap
Quoting howarjo1943:
Yeah, its a blackout. Type "satellite blackout" into a search engine and click on the Wikipedia page that comes up. It has a schedule of the blackouts which I think started on Aug 13 and go through early October.



Thats a good read then.
I believe StormJunkie Has that link,Ill nab it from him In the am.

Thanks for the info
Member Since: July 3, 2005 Posts: 421 Comments: 127650
3822. Drakoen
Blackout is just delaying the satellite images. They will just update slower.
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3821. Patrap
Cleaned up Loop with Smoothing engaged and Clutter removed


Member Since: July 3, 2005 Posts: 421 Comments: 127650
3820. Wariac
any possibility that this could be a one two punch for the nothern greater antilles (specially Puerto Rico)?
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Yeah, its a blackout. Type "satellite blackout" into a search engine and click on the Wikipedia page that comes up. It has a schedule of the blackouts which I think started on Aug 13 and go through early October.
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3818. jipmg
wait? TD 2 has 62mph winds being recorded?
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3817. Drakoen
5z:

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I give all the credit to skyeponey but look to the straits of fl. for the first action of the year. Patrap see's it I believe.
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am i the only one who thinks 90l should be td3 already? the convection looks as if its fixing to wrap up the eastern side of circulation, and im sure when that begins this thing will wrap up quickly.
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Quoting leftovers:
you have seen nothing yet if this small storm gets in the fl. straights it could bomb out with the right environment .


Charlie was a small storm...it does not take much for a small storm to crank up real fast.
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3813. Drakoen
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Quoting leftovers:
you have seen nothing yet if this small storm gets in the fl. straights it could bomb out with the right environment .


Yep.. HWRF depicts this.
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Quoting jipmg:
anyhow, anyone have an idea why satellite images have yet to be updated?


There in blackout i suppose......i didn't realize they was still doing this...they save batteries on the Satellites as they use solar power so when the sun is not recharging them during the nite they go into Blackout for i think 2 hrs i believe this is correct.
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The Atlantic has come alive. The talk of a below average season could soon quiet a bit. It is entirely possible for the "D" storm to be attained before next weekend. Ana and Bill now almost seem like a given with TD 2 and 90L both looking impressive. IF the Gulf system and the new wave the GFS shows developing off Africa form,(Big if's) we could have D storm by Aug 20th. That would be amazing considering there were no named storms through Aug 14th.
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3808. Patrap
The GOES Sats and others must be in Blackout,..someone has a schedule somewhere.
Member Since: July 3, 2005 Posts: 421 Comments: 127650
3807. KEEPEROFTHEGATE (Mod)
Quoting Walshy:


Thats when recon goes in and tells everyone they are just doing a drop-sound when they are really seeding it.
well i better not tell ya about my ultra sonic atmospheric wave degeneration device i have on the roof of the high rise i look after that will really spook ya
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3806. ackee
TD#2 be Ana BY 5pm would not be suprise if it tracks into the carrb
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3805. 7544
Quoting jipmg:
anyhow, anyone have an idea why satellite images have yet to be updated?


in blackout the return in one hour then you cann see the difft ones newest
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3804. jipmg
anyhow, anyone have an idea why satellite images have yet to be updated?
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3803. jipmg
Quoting 7544:
man did this change in the last 5 hours

ts anyone ?

CI# /Pressure/ Vmax
3.4 / 995.2mb/ 53.0kt


rapid intensification is occuring, I was afraid of this
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3802. ackee
Quoting TampaSpin:
I think the GFS model is really screwed up and will take a few cycle runs to get things staightened out...
agree
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Quoting leftovers:
does anyone know what yr s fl got hit by three cyclones?


2004 had Charley, Frances, Ivan and Jeanne. We got hit with Frances and Jeanne where I live. The year after that we had Wilma.
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3800. KEEPEROFTHEGATE (Mod)


latest as of 415 utc
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3799. Patrap
Member Since: July 3, 2005 Posts: 421 Comments: 127650
3798. sfla82
Quoting Funkadelic:


I can only imagine what the news will be like in Florida starting on Monday LOL.. They love to scare and hype


Yeah I know!!!! And everyone always fall for the hype too! LOL!
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Quoting leftovers:
does anyone know what yr s fl got hit by three cyclones?


2004 by 4 separate systems, 2008 4 times by one system.
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3796. sfla82
Quoting Funkadelic:


I can only imagine what the news will be like in Florida starting on Monday LOL.. They love to scare and hype


I know...And everyone always falls for the hype too!!! LOL
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3795. Walshy
Quoting weatherboykris:


There's a blackout each night from around now until ~4AM.


Thats when recon goes in and tells everyone they are just doing a drop-sound when they are really seeding it.
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I think the GFS model is really screwed up and will take a few cycle runs to get things staightened out...
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3793. JRRP
Quoting Skyepony:
Keeper that Lat you posted. 02L had a pretty good wobble south.

14/2345 UTC 15.2N 44.9W T1.5/1.5 02L

if that is correct then TD2 is moving in south track
Link
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Good night, everyone. Safe, peaceful sleep to all.
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Quoting leftovers:
its a conspiracy did you know jerry garcia is still alive cia i heard


There's a blackout each night from around now until ~4AM.
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3789. KEEPEROFTHEGATE (Mod)
Quoting Skyepony:
Keeper that Lat you posted. 02L had a pretty good wobble south.

14/2345 UTC 15.2N 44.9W T1.5/1.5 02L
just a little wobble

lol
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3788. Skyepony (Mod)
Guillermo
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3786. sfla82
Quoting TampaSpin:


I was just getting ready to post the same thing


Nah! It will most likely do what they always do with the curve right before it hits S. Fla. It amazes me how they do that all the time. With S. Fla already being in the cone, we should be safe as we always seem to fade out of it.
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3785. Drakoen
Quoting jipmg:
why haven't we gotten satellite updates in the past hour?


good question
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3784. BenRMac
Hey all, looks like something is finally happening in the Atlantic. This place has become a lot more crowded since I left.
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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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