97L growing more organized, will bring heavy rain to the Lesser Antilles
The tropical wave near 12N 52W, about 600 miles east of the Lesser Antilles Islands (97 L), has grown more organized this morning as it tracks west at about 20 mph. This wave is surrounded by an area of very dry air from the Sahara Desert, but 97L has been able to steadily moisten a large region of the atmosphere over the past day, insulating itself from the dry air. This moistening process has been aided by sea surface temperatures (SSTs) that have steadily increased from 26.5°C to 27.5°C, plus the presence of only 10 knots of wind shear. The system now has a small area of intense thunderstorms near its center, with some rotation of the cloud pattern evident at mid-levels of the atmosphere. An upper-level outflow channel has opened to the north, and there is evidence that surface spiral bands are beginning to form. This morning's QuikSCAT pass missed 97L, so we don't know what is happening at the surface.
Wind shear is a modest 10 knots over the disturbance, and is forecast to remain in the moderate 10 - 15 knot range through Monday morning. This should allow further development to occur today, and 97L could be approaching tropical depression strength on Monday as it moves through the central Lesser Antilles Islands. Monday night, shear is expected to rise to 20 - 30 knots, thanks to the presence of a trough of low pressure at upper levels of the atmosphere over the eastern Caribbean. Since 97L is a relatively small system, it is very vulnerable to wind shear. This shear may be able to drive some of the dry air west of 97L deep into its interior, significantly disrupting the disturbance. Shear will remain high along 97L's path through Thursday, when the storm should be in the western Caribbean near Cuba. If there is anything left of 97L by then, some development is possible. The National Hurricane Center gave 97L a low (less than 30% chance) of developing into a tropical depression in the next 48 hours in their 8am Tropical Weather Outlook. However, I'd say the odds are now in the medium range (30 - 50%).
None of the computer models are forecasting tropical storm development over the next seven days.
Figure 1. Current satellite image of African wave 97L.
I'll have an update Monday morning. As 97L approaches the islands, you may want to follow local observations there using our wundermap for 97L.
Jeff Masters
Reader Comments
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It sure is, this is the one I've been mentioning.. see the anticyclonic turning? It's an Anticyclone.
http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8shr.html
Yeah. It's in the ITCZ, but if it can escape it could get interesting
On the satellite I'm seeing something that looks life a subtropical ridge. I could be wrong though.
Shear is predicted to lift in 2-3 days. Maybe even less.
Yeah. I'm wondering if they'll deactivate it again.
I think it was the NOGAPS
Unlikely. The 850mb vorticity continues to increase. The convection may be gone but the circulation is still there.
Don't write it off. Remember if the circulation survives the axis will move west and meet up with the anti cyclone
ABNT20 KNHC 200546
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT MON JUL 20 2009
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
CLOUDINESS AND SHOWERS ASSOCIATED WITH A TROPICAL WAVE LOCATED A
COUPLE HUNDRED MILES EAST OF THE WINDWARD ISLANDS HAVE BECOME LESS
ORGANIZED OVER THE PAST SEVERAL HOURS. UPPER-LEVEL WINDS ARE
EXPECTED TO BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS
SYSTEM OVER THE NEXT 24 TO 48 HOURS. REGARDLESS OF DEVELOPMENT...
LOCALLY HEAVY RAINFALL AND GUSTY WINDS COULD AFFECT THE WINDWARD
ISLANDS DURING THE NEXT DAY OR SO AS THE WAVE MOVES WESTWARD AT 15
TO 20 MPH. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER PASCH
Yeah. Looks pretty good on the RGB. And it kinda looks like its starting to go a little more northerly. or that could be because of the convection flaring up.
Both of us knew it was going to hit the brick wall of shear.
There was believers and wishcasters.........LOL
I ain't writing it off. still has a slim chance imo
lol
Just some itcz flare ups.
agree
Your so wrong......go back and look at my quotes...i said it was under 10-15kts of shear..even last nite and it would increase....today and tonite....ROFLMAO.....Wishcaster!
I strongly agree with you....if the Shear would not have been present 2 days ago along with the dry conditions and cooler waters...we could have had Ana already present.
Many probably did the same to you!
Ok....whatever along with your buddies.....its all good!
And yes i think i know that....hahaha
Look at the vorticity. Increasing every 3 hours. The pressure has dropped 3 millibars in the past 24 hours
Wow Tampa, serious whats your problem this year? Calling wishcasters, insulting people, ect. You weren't anything like that last year.
Honestly the shear was 15kts the other nite.....out of the NW.....if you would have zoomed in you could see the cloud tops blowing off.......5kts of shear does not cause that.....Yes it still bears some watching but, not much....LOOK East and watch the GOM and off the Atlantic seaboard the next few days.
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