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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As snaggle pus would she both systems are exiting stage left headed wsw I presume.
Member Since: August 18, 2008 Posts: 0 Comments: 3112
Nightline is about the drought here in Texas...so sad. I drove up to New Braunfels, Tx last weekend and it was just so devastating seeing all the dead crops on the way. We need rain but no hurricanes. Just RAIN!
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Quoting CaneWarning:
The met I just watched on tv doesn't seem as concerned as he did a couple of days ago.


I agree not to over react but, don't under play what might be also.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting extreme236:
First 02L advisory was a special one, which came out one hour after the usual time:

600 AM AST TUE AUG 11 2009
can u post ur "illegal" site again, thanks!
Quoting TampaSpin:
I know its Obama's fault ......he cancelled funding for NHC just before the update......LMAO


Quick someone bail out the NHC!
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Who on here thinks that FL is really in the bullseye with 90?>
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3328. KEEPEROFTHEGATE (Mod)


T.C.F.A.
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guys can we get back on too 90L and TD 2 can we Please
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Quoting canesrule1:
00Z models out for 02L. Pointing at Florida, mostly SFLA:Link


Yikes.
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I've yet to see the ATCF website be wrong yet (even when they had 02L as a TS it was changed back before the advisory time)...I can only assume there will be a special advisory right now.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
I know its Obama's fault ......he cancelled funding for NHC just before the update......LMAO
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Good night!

The way I see it, there will be T.D. 2 by 2:00 AM, and T.S. Ana and T.D. 3 by 5:00.
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Quoting WPBHurricane05:


LOL...have a cookie:

awwwwwwww, he deserves it!
Quoting DestinJeff:


you've done well. take a break. you might say..."refresh yourself"


Yeah man, take 5! :D
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Has Walmart run out of SPAM yet???
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3317. JRRP
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Quoting antonio28:


I think models are usefull when they agree on a forrescast like 90L one, always have the error marging but they are a good guidance in short term (120 hrs).

Yes, I was mostly talking about all of the not so useful posts...like this one.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
They got 20 dropsonde observations into the GFS 00Z cycle.
Member Since: September 23, 2005 Posts: 14 Comments: 10942
Quoting BajaALemt:
((( Baha!! .. with an H ))) Just in time (maybe) for the TWO! Good to see you!
Hey, I checked over there, and I don't see anything...... luckily the blog is here to keep me entertained....
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Think about it - we all know the NHC comes here for their information. They got the virus! No updates until they finish running the anti-virus.
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Quoting sammywammybamy:



Back to Serious Mode:

I think i actually made alot of Serious and Worried People Laugh...

But my hands really do hurt OUCH..


LOL...have a cookie:

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August 15, 2009

Historic WU events: 2

1) Two tropical depressions form simultaneously

2) 320 bloggers banned simultaneously
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First 02L advisory was a special one, which came out one hour after the usual time:

600 AM AST TUE AUG 11 2009
Member Since: August 2, 2007 Posts: 19 Comments: 19234
3308. viman
Quoting canesrule1:
same here im going to watch this till 2


I'm not, I'm going to bed... I got a long day tomorrow and probably a longer day on Sunday depending on what these systems do... Good Nite all till in the morning.
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Working for the NHC would be like being the president; no matter what you do you always have the peanut gallery. From what I can recall, they(besides the storm in the gulf that prob. was a trop. storm) have called it pretty well. IMO.
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00Z models out for 02L. Pointing at Florida, mostly SFLA:Link
3305. tbrett
Ya'll are sooooooo funny LOL
Member Since: July 20, 2007 Posts: 0 Comments: 107
baja, yep sure did i am assuming it's from that crap in teh carrib...think it's supposed to move pretty quik...3-5' seas sunday morning...fingers crossed....catch any of that swell last sat?
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Yes, it does look very obvious that 02L is taking a WSW shift. Agreed?
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stay tuned................................. maybe NHC still has dial-up
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3300. jipmg
someone seriously needs to call them..
LOL Ike! 8 hours later, he'll have used up all five fingers and won't be able to post the TWO :)) :))
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The met I just watched on tv doesn't seem as concerned as he did a couple of days ago.
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Quoting TampaSpin:
I would say there might be some difference of opinions going on at NHC.....


I would agree. If I had to guess, it would be whether they should classify 90L if they were gonna classify 02L considering the former is better organized appearing.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
But sometimes the NHC can be wise being conservative, for example, if you worked at the NHC, would not want to jump the gun as a forecaster, you would want to make sure before you tell the public a TD has form, you meet all the requirements and last, you dont want to have 30 stupid looking tropical cyclones.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting TampaSpin:
I would say there might be some difference of opinions going on at NHC.....


"Its clearly a flock of sea gulls."
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Quoting presslord:
Where the heck is JFVWS?!?!?!?!


Shuttering up his home
Member Since: May 17, 2009 Posts: 0 Comments: 559
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local news in charleston, SC (2 diff channels) said former td2 trying to reform...center reforming south of previous one...and 90l still bout the same...has more convection than former td2 but not symetrical just yet
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Quoting tiggeriffic:
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

best idea i have heard tonight....lololol
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GUYS no advisory till 2am,THEY ISSUED IT AT 8PM,issue it every 6 HOURS!
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over 6 pages of posts gone in 17 minutes, damn! and its all Sammy's fault!!! LMAO, jk.
3287. IKE
Quoting sammywammybamy:
f5...f5...f5..f5..f5................f5..............f5................................f5....f


8 hours later....checks on Sammy.....

F5...F5....F5....uh...think you can give up now!
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Quoting Patrap:
..You dont think WS took the NHC Hostage and is Typing the 11pm ,..and that's why its Late..?





if he's typing it someone's gonna have to translate it into English...
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I would say there might be some difference of opinions going on at NHC.....
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting atmoaggie:

But how many of them are useful?


I think models are usefull when they agree on a forrescast like 90L one, always have the error marging but they are a good guidance in short term (120 hrs).
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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.