Dr. Jeff Masters' WunderBlog

97L growing more organized, will bring heavy rain to the Lesser Antilles
Posted by: Dr. Jeff Masters, 15:55 GMT le 19 juillet 2009 +1
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
Categories: Hurricane
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2351. weathermanwannabe 13:45 GMT le 20 juillet 2009    
Quoting canesrule1:
those models keep on getting closer to S-FL, scaring me a bit now.


No need to worry; this is not going to make it to South Florida.......Don't take my word for it...You only have to worry down the road when NHC officially declares a tropical storm or hurricane watch for your area.......On a related note, if you have a hurricane plan in place and have bought supplies in case, there is no need to worry....Take care of these items during this "lull" if you have not already done so...........Dont' Worry...Be Happy...... :)
Member Since: 8 août 2006 Posts: 0 Comments: 6703
2352. stormsurge39 13:46 GMT le 20 juillet 2009    
1010 pressure was the last one that was posted and its the lowest yet.
2353. StormFreakyisher 13:47 GMT le 20 juillet 2009    
Okay I have two questions.Is all that rain and cloudiness east of the Bahamas the remnants of the tropical wave that was sheared apart and is interacting now with a frontal boundary that will make it form into somethin?And what will happen with the tropical wave in the mid atlantic that is still holding a pouch of thunderstorms?
Member Since: 16 mai 2009 Posts: 0 Comments: 684
2355. Drakoen 13:48 GMT le 20 juillet 2009    
Quoting BurnedAfterPosting:


morning Drak, yea I agree, seems to me that it is fighting fairly well though, not just dying out


I don't think it's done yet.
Member Since: 28 octobre 2006 Posts: 57 Comments: 29010
2356. canesrule1 13:49 GMT le 20 juillet 2009    
i will
2358. canesrule1 13:50 GMT le 20 juillet 2009    
Quoting stormsurge39:
1010 pressure was the last one that was posted and its the lowest yet.
i posted a 29.83
2359. BurnedAfterPosting 13:51 GMT le 20 juillet 2009    
NEW BLOG!!
2360. canesrule1 13:51 GMT le 20 juillet 2009    
Quoting StormW:


Good...you?
im doing good, following those models, just wondering do you believe we might have our first named system of the season with 97L or is this just going to die?
2361. jurakantaino 13:52 GMT le 20 juillet 2009    
Ghotar- From now on anything that come out of Africa should be interesting, since we are approaching rapidly Cape VERDE season.
Member Since: 31 juillet 2008 Posts: 0 Comments: 730
2362. moonlightcowboy 13:52 GMT le 20 juillet 2009    
Good morning. I see 97L survived the night with the "dreaded" shear.

GFDL does not do cyclcogenesis, folks. 97L maintained despite the shear, still moving with steering mostly westerly, big convection there with dmax from all the lift. LLC? Can't see it. MLC, difficult too; but, I imagine it's still there - it's just grappling with how to manage all that convection now. ;)

Member Since: 9 juillet 2006 Posts: 179 Comments: 28121
2363. Grothar 13:53 GMT le 20 juillet 2009    
I agree with the comments on The Weather Channel. One must infer from their format that they believe they are the focus of the show, when in fact the weather is secondary. Weather, in itself is dynamic. They interject themselves in front of the maps so you cannot see the "massive storms and fronts, etc". It should be more informative and precise.
Member Since: 17 juillet 2009 Posts: 57 Comments: 19552
2364. Mikla 14:04 GMT le 20 juillet 2009    
97L with some models and mid & upper shear...
Member Since: 13 octobre 2006 Posts: 0 Comments: 201
2365. msphar 14:10 GMT le 20 juillet 2009    
Burned - you still believe in your Westward thesis or was it SW? Looks to me like it gained a degree Northwards overnight while it moved West 7.5 degrees.
Member Since: 20 août 2006 Posts: 0 Comments: 258

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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.

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