TD 2 nearly dead; African disturbance 90L gathering strength

By: Dr. Jeff Masters , 2:38 PM GMT on August 13, 2009

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Tropical Depression Two is near death, but is still worth watching. The dry, Saharan air to the north and west of the depression, combined with moderately high levels of wind shear of 15 - 20 knots, have almost completely destroyed all of TD 2's heavy thunderstorms. Satellite loops of the storm show a well-formed circulation, but almost no heavy thunderstorm activity.

Wind shear over TD 2 is expected to remain in the modereate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C three days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly, and some of the models indicate the TD 2 may get destroyed in the next day or two. However, several models still predict TD 2 will become a tropical storm. The HWRF model predicts TD 2 will become a hurricane five days from now, but this seems unlikely given the dry air and relatively high wind shear affecting the storm.


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

African tropical wave 90L
A strong tropical wave with a large circulation and plenty of heavy thunderstorm activity is a few hundred miles south of the Cape Verdes Islands, off the coast of Africa. NHC dubbed this disturbance 90L this morning. This morning's QuikSCAT pass shows that 90L has a very large circulation, and top winds of about 30 mph. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are in two major bands, to the north and to the south of the center. There is no heavy thunderstorm activity near the center yet, and this would have to happen before 90L can be named Tropical Depression Three. 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 has been. Wind shear is about 20 knots over 90L, and is forecast to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days, which are high enough above the 26°C threshold for tropical cyclone formation to allow some slow development to occur. The GFS and ECMWF models continue to predict the development of this wave, though they are now less aggressive about intensifying it than they were in earlier runs. The consensus among the reliable HWRF, GFDL, GFS, and ECMWF models is to bring 90L to point near or just north of the northernmost Lesser Antilles Islands 6 - 8 days from now. The storm could be at hurricane strength by then, as forecast by the SHIPS intensity model.

I'll have an update Friday morning.

Jeff Masters

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hey orca...looks like not much has changed since last year...roflmao...
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Local news showing the first images form the local news station reporters just hours after Katrina..wow..feels just like it was yesterday..such sad memories
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well...surfers in the GOM region...waxem up!!!.....sat hard east winds...sounds like long lefts to me!!!!
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2060, looks as if we could be getting some rain for my birthday on Sunday if this wave makes it to New Orleans
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Quoting TampaSpin:


OK OLD TD2's Low will enter the Caribbean.....LOL


Had to pull your chain LOL

Well, if it does not regenerate I would expect the remnant low to dissipate before having a chance to enter the Caribbean. If it does regenerate then my thinking would still be for a pass to the N of the Islands.

Either way I stand by my thinking that it started too far N and too far East to enter the basin.Ironically, having started as far N as it did resulted in all the dry air and low SST that caused it to weaken and move further W than forecasted. Now there you have a twist for the books eh ?
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New Google Graphic
EUMETSAT Real time imagery that updates every 15 minutes.

Look at the next blob coming off Africa..
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everyone, I'm pretty sure tomorrow when all you wake up, we will have 03L, Good Night.

-CanesRule1
I got fooled by an "old" image earlier from GOES East....

This looks more like current conditions:

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2576. Patrap
Quoting weatherman874:


what is the name of this satellite? I cant find it


What Post Number friend..?
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Maybe I'm thinking too bullish, but 90L looks rather impressive right now and appears on track to become a TD very soon.
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Quoting 7544:


if it has another good dmax it may get stronger imo no dry air around too have to keep one eye on this one
high pressures plus shear make for poor chance of near term deveopment
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2571. Patrap

Area forecast discussion
National Weather Service New Orleans la
757 PM CDT Thursday Aug 13 2009


Update...
..sounding discussion...


The atmosphere remains relatively dry with a significant amount
of dry air above 600 mb and a precipitable water value of 1.51
inches. Isolated showers developed during the afternoon but most
dissipated relatively fast. Winds are out of the east in the lower
levels shifting to north in the middle levels and west in the upper
levels...good directional sheer.


&&


Previous discussion... /issued 347 PM CDT Thursday Aug 13 2009/


Short term...


Not much change in the overall thinking with this forecast
package. An unusually dry and fairly stable airmass remains in
control of the region this afternoon and will continue to dominate
the area into tomorrow. Only some isolated convective activity is
expected near coastal and tidal lake interfaces...due to enhanced
lift along any seabreeze/lakebreeze boundaries. In
addition...a more unstable airmass near the dissipating frontal
boundary in the northern Gulf will continue to bring isolated to
scattered convection to the coastal waters through tomorrow. Ample
low level moisture below the upper level cap will allow for plenty
of cloud development during peak heating hours once again
tomorrow. With these clouds in place...temperatures should not
skyrocket...but rather remain near normal. However...overnight
lows should dip slightly below normal...especially north of the
I-10 corridor tonight...due to the dry airmass in place.




Conditions begin to change markedly going into the weekend. A
strong and fast moving tropical wave currently over hispanola will
quickly pull into the eastern Gulf by Saturday. As the tropical
wave pulls closer to the region...moisture will quickly return
back into the region. As a result...expect a return to more normal
August conditions on Saturday...with scattered convection in the
afternoon hours. However...the convection will be somewhat limited
by the fact that the region is on the western...or more subsident
side...of the tropical wave. These same conditions will hold true
into Saturday night...even as the wave quickly moves toward the
central Gulf Coast. Keep chance probability of precipitation in for Saturday night in the
coastal waters and along the coast...with more isolated activtiy
farther inland. However...do not expect any heavy rainfall at that
time...as the deepest tropical moisture remains on the eastern
side of the tropical wave
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2566. 996tt 3:04 AM GMT on August 14, 2009
swell coming?


you know it.....
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This is TD2
Member Since: July 11, 2006 Posts: 14 Comments: 11173
Quoting Patrap:


what is the name of this satellite? I cant find it
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Quoting Chicklit:
intelligent looking ????
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2566. 996tt
swell coming?
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Quoting kmanislander:


TD2 will not enter the Caribbean because it no longer exists.


OK OLD TD2's Low will enter the Caribbean.....LOL
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2562. 7544
Quoting sammywammybamy:



Orca,

By The Wave Near Hispanola?


if it has another good dmax it may get stronger imo no dry air around too have to keep one eye on this one
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zoo! how's tricks? naw...eyeore been drinking too much for me...lol...
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Good to see everybody - off to sleep for me.
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Quoting sammywammybamy:



Orca,

By The Wave Near Hispanola?


Yup.. I would say quite wet.
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Quoting zoomiami:
Tigger!!!! Though you were lost with Eyeore.


Its a good night.. lots of last year people popping in :)
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2556. Patrap
risingtidenola.org






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SITE DESIGN BY VARG - ART BY GREG PETERS
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Quoting Orcasystems:


Not yet.. but here is an update for you.. your going to get wet :)


not yet as in yes there is as 11 update, or not yet as in only when we have better than an invest?

Yes - we are going to get wet
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Quoting Chicklit:
Greta Van Sustren is a disappointment.
She is an intelligent looking woman, albeit a weird-looking one, that appears as if she could say something and then says nothing at all.
Member Since: July 11, 2006 Posts: 14 Comments: 11173
Quoting Vortex95:


Me too even a vigorous wave hitting us in S Fla it may be an issue. Have had some bad stuff happen from waves i.e. 2000 flood from pre- ts leslie.


If it goes in the GOM, there could be a shot for development, but that's all what if's.
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Quoting Orcasystems:


Not yet.. but here is an update for you.. your going to get wet :)



lol
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Quoting tkeith:
I think (without any facts to back it up,mind you) the wave over Hispanola is gonna get me wet here in NOLA.


yeah i do too, I'm here in Lakeview and i wouldnt say we could desperately use the rain but it would sure be helpful
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Quoting TampaSpin:


Kman, there appears to me a good chance TD2 will now enter into the Caribbean.


TD2 will not enter the Caribbean because it no longer exists.
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Quoting tkeith:
I think (without any facts to back it up,mind you) the wave over Hispanola is gonna get me wet here in NOLA.


Dude! Outstanding to see you here!
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Quoting atmoaggie:

Hey, you are correct. Nevermind. Back to the "Caribbean wave is a big nuthin" mood. Pfffft pending.

I kind of agree. I dont see it doing anything short of failing with the upper Low over the wave. When vorticity is like 3 times better at 300mb than the surface? Um, not developing anytime soon. I will say it has good divergence but with surface divergence too we just have a big mess.
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2544. 7544
ok i have a dum question if this 18gfs holds on the way it has been showing this strong strom over to so fla will they get warned way ahead of 3 or 5 days to get ready not saying its going to hit in anymatter just asking scince katrina was will they have they change the watches in the event a cat 5 or higher isheaded their way for most to evacuate and get supplies cause fla is a very big state . cause its been along time that fla was threaten with a major cat 5 thanbks for redaing
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Quoting zoomiami:
Is there an 11:00 update tonight?


Not yet.. but here is an update for you.. your going to get wet :)
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Tigger!!!! Though you were lost with Eyeore.
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Orca! How goes it?
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Quoting louisianaboy444:
Gotcha. I appreciate it.

I'm going to bed, goodnight everyone.


Oh wait almost forgot didn't you want to talk about schools

He's going to A&M, like he should...(j/k)
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Quoting kmanislander:
Good evening

So, another ho hum evening waiting for the tropics to do something ?



Kman, there appears to me a good chance TD2 will now enter into the Caribbean.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
I don't think the Caribbean wave will develop. The convection looks impressive only because of the ULL. As the NHC said, no significant development is expected. However, I'm keeping an eye on it due to it's proximity to land.
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Quoting tiggeriffic:
Hello all...hard to believe it's been almost a year since we were all here doing this last year...except last year we started WAY before this...el nino, la nina...let's see what happens in the next couple days...


hey neighbor
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.