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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Ana went from a cute little thing to a Big Gal. They need lovin too!
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Herbert box alert!But NHC projects it to be a depression by then other models still take it as a TS over the herbert box.
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Quoting canesrule1:
WOW! i just calculated that 90L is 1081.8 miles in diameter! in comparison Gilbert in 88' was around 800 miles in diameter at peak intensity!


Dont panic and stop making people afraid.
TD2 and 90L are both going west and i know this for sure because the NHC has called me.
The men who called me named WESTwood,the brother of Clint EASTwood.
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Quoting hurricanejunky:
90L is monstrous! Good Lord. If that circulation stays that size and is able to develop it will rival Ike or Floyd. Pretty ominous looking Cape Verde system.
yeah, i calculated its over 300 miles bigger in diameter than Gilbert 88' at peak intensity!
Quoting hurricanejunky:
90L is monstrous! Good Lord. If that circulation stays that size and is able to develop it will rival Ike or Floyd. Pretty ominous looking Cape Verde system.


Remember, when Ike was in the CATL it was a pretty small, tightly wound system. It wasn't until it hit the Gulf that it exploded in size.
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That circulation will likely tighten up though as it's still kinda broad.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting Acemmett90:

crap can you say andrew


No that's Ana-drew
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There have been many "Ana" storms, (1979, 1985, 1991, 1997, and 2003)and none of them have been bad. This one, if it becomes Ana has the chance to be an exception, but let's hope not.
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What are the odds we see TD3 today? All that false Ana talk yesterday made my mouth water now I'm very anxious for something to strengthen!
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Quoting Acemmett90:

it trying to hit the whole east coast at once CRAP
LOL, i think this will be the largest hurricane ever recorded once it reaches peak intensity, i think instead of ANA, it should be called Typhoon TIP senior.
what is a floater
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Why is every CV storm headed in a W or WNW direction the next omg "Andrew"?
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90L is monstrous! Good Lord. If that circulation stays that size and is able to develop it will rival Ike or Floyd. Pretty ominous looking Cape Verde system.
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Quoting CaneWarning:


Pressure falling
very anticipated i think it will be by 1007 millibars before 5PM EST.
12Z GFS... running. Initializing TD#2 as a 1012MB Low and 90L as a 1011MB Low.

Let's see how it wants to develop these...
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Quoting TampaSpin:
So will Bill need a SEx change or not...LOL
i think sex change will be needed, lol.
Quoting Acemmett90:

crap can you say andrew
ANDREW, lol
Quoting nrtiwlnvragn:
Update bouy at 12N 23W as of 10AM EDT



Pressure falling
Member Since: April 26, 2009 Posts: 3 Comments: 3667
WOW! i just calculated that 90L is 1081.8 miles in diameter! in comparison Gilbert in 88' was around 800 miles in diameter at peak intensity!
Update bouy at 12N 23W as of 10AM EDT

Member Since: September 23, 2005 Posts: 13 Comments: 10458
161. 7544
looks like the strom everyone thought will be called bill will be ana after all which is 90l
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Quoting Acemmett90:

i know


So yesterday's predicted Bill will become Ana.
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Quoting P451:


Already up.

Link


There's a floater on the SSD site
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So will Bill need a SEx change or not...LOL
Member Since: September 2, 2007 Posts: 177 Comments: 20430
Quoting Acemmett90:

i know

I dont know.
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Member Since: March 19, 2009 Posts: 0 Comments: 1419
convection increasing and expanding N near the center of TD2
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Quoting Acemmett90:

37 knots how fast is that
Exactly 42.6mph
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Already a floater waiting on 90L lol
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Quoting Acemmett90:

yah it would be the end of nola
yup
Quoting 7544:


10 day gfsx you be the judge pretty close

Link
wow
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The amount of atmosphere that 90L is turning will take it a while to tighten up but, the large amount of area that will be spinning, this could become a very large wind field hurricane down the road. Look at the size of TD2 and even the Canes in the Pacific compared to 90L.....its enormus is size.
Member Since: September 2, 2007 Posts: 177 Comments: 20430
Convection is firing closer to 90L's COC.
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Quoting Acemmett90:

Pray to God nothing gets into the gulf
lol, well if current 90L models are correct its anticipated to go threw SFLA into the Gulf and then into NOLA, but 90L is over 3000 miles out and chances of that are very slim.
Quoting Acemmett90:

37 knots how fast is that

Around 42.5 mph
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About JeffMasters

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