High wind shear ripping into 97L

By: Dr. Jeff Masters , 1:49 PM GMT on July 20, 2009

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A strong tropical wave (97L) a few hundred miles east of Barbados in the Lesser Antilles Islands has grown less organized today as it tracks west at 15 - 20 mph. The wave is moving underneath an upper-level trough of low pressure, which is bringing 30 knots of wind shear to 97L. While there is a respectable amount of heavy thunderstorm activity associated with 97L, there is no longer any low-level spiral banding or rotation of the cloud pattern. This morning's QuikSCAT pass at 5:35 am EDT showed sustained winds of 35 mph a few hundred miles east of Barbados, but there was no surface circulation evident. The islands of Barbados, St. Vincent and the Grenadines, St. Lucia, and Martinique can expect heavy rain and wind gusts to 50 mph as 97L moves through the Lesser Antilles Islands this afternoon and tonight, but 97L will not become a tropical depression.

Wind shear along the path of 97L is forecast to remain in the high 25 - 35 knot range for at least the next three days. This should prevent further development of 97L, and I expect the disturbance will be gradually torn apart during the next few days. The National Hurricane Center gives 97L a low (less than 30% chance) of developing into a tropical depression in the next 48 hours. None of the computer models are forecasting any tropical storm development over the next seven days.


Figure 1. Current satellite image of African wave 97L.

I'll have an update Tuesday morning. As 97L moves through the islands, you may want to follow local observations there using our wundermap for the region.

Jeff Masters

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Convection looks to be exploding just north of the circulation if my eyes don't deceive me.
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Quoting btwntx08:

in what areas are they decreasing

Western and eastern Caribbean and IMO it's looking a bit better in the central.
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Gaining Divergence:


And also Convergence:
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Increasing vorticity:
850mb:


700mb:


500mb is finally spreading:


The system is becoming better stacked
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Shear decreasing rapidly and increasing in some areas by a smaller amount:

NOW;



3 hours ago:
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Quoting btwntx08:

is that by the bahamas??


Yes in the bahamas
Member Since: September 2, 2007 Posts: 177 Comments: 20430
The new convection that just popped up, is that right north of the circulation? I am speaking of 97L of course.
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2353. HadesGodWyvern (Mod)
yup it has been overland for nearly 12 hours now.. with that advisory
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Quoting HadesGodWyvern:
India Meteorological Department
Tropical Cyclone Bulletin Number SIX
DEEP DEPRESSION BOB03-2009
8:30 AM IST July 21 2009
===================================

Subject: Deep Depression over north Orissa.

At 3:00 AM UTC, Deep Depression BOB03-2009 over north Orissa moved westwards and lays centered over north Orissa, close to Jharsuguda.

The system is likely to move in a west-northwesterly direction and weaken gradually.

----
still a deep depression..

lol, still
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Quoting druseljic:


Thanks again Tampa! I have found your updates quite informative for some time now. I also appreciate all the graphics you share, helps us lurkers to keep up :-)


Thanks and good nite everyone......
Member Since: September 2, 2007 Posts: 177 Comments: 20430
2349. HadesGodWyvern (Mod)
India Meteorological Department
Tropical Cyclone Bulletin Number SIX
DEEP DEPRESSION BOB03-2009
8:30 AM IST July 21 2009
===================================

Subject: Deep Depression over north Orissa.

At 3:00 AM UTC, Deep Depression BOB03-2009 over north Orissa moved westwards and lays centered over north Orissa, close to Jharsuguda.

The system is likely to move in a west-northwesterly direction and weaken gradually.

----
still a deep depression..
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Quoting reedzone:
GFS, GFDL, CMC, EURO, and yes the NOGAPS now forecast 97L to regenerate, or at least the remnants of it near the Bahamas and become our first named storm.


Hum.....not sure thats any part of 97L...Maybe tho.
Member Since: September 2, 2007 Posts: 177 Comments: 20430
New CIMSS maps in 8 mins
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I'm watching 97L because it is of the most threat to me now.
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Need to watch 27N 74W
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If nothing else, it will be interesting to watch...
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Convection trying to refire:

Wonder if it can do it
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Quoting TampaSpin:
TampaSpins Tropical Update


Thanks again Tampa! I have found your updates quite informative for some time now. I also appreciate all the graphics you share, helps us lurkers to keep up :-)
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GFS, GFDL, CMC, EURO, and yes the NOGAPS now forecast 97L to regenerate, or at least the remnants of it near the Bahamas and become our first named storm.
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Quoting TampaSpin:
Sorry i had some typo's i fixed! I wish there was a spell check system in place....LOL


Yeah, they really do need a spellcheck system.
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Sorry i had some typo's i fixed! I wish there was a spell check system in place....LOL
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TampaSpins Tropical Update
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2337. msphar
bedtime for me.
Member Since: August 20, 2006 Posts: 0 Comments: 289
got a bit of a flare up to the east of the swirl now as well. this thing is really trying it's best to regain some convection over that circulation.
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2335. msphar
I'm wishing it dead and buried. It time for the next bowling ball to come down the aisle.
10 more weeks of this watchful waiting as about all I can take anymore. I/m too old for this game.
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Quoting msphar:
And so ends the long sad tale of 97L, the little Invest that tried and tried but failed to deliver in the end. Oh well, on to the next blob. One of these is going to be the A storm.

don't count it out it has strong vorticity. If it can maintain it and get under the anticyclone we may have a problem
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2333. msphar
And so ends the long sad tale of 97L, the little Invest that tried and tried but failed to deliver in the end. Oh well, on to the next blob. One of these is going to be the A storm.
Member Since: August 20, 2006 Posts: 0 Comments: 289
Is it me or is the convection converging
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21st of july ... I really think we'll see a ramp in august but don't see much happening as we near the close of July. Will keep an eye on it however =] Don't cal it a bust season just yet guys no telling what augseptoct holds
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Looks like the convection is trying to converge
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Looks like a little bit of convection is forming from a little north of the low swirl.
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Quoting tennisgirl08:
Poll for rest of July:

1) no named storm
2) 1 named storm
3) 2 named storms
4) more frustrating invests!!!

I'd have to say #4......oh look something is happening...no wiat....there is sheer,dust or what have you stopping it. I kinda wonder if anything is going to form this year....yeah yeah, I know....this is only July.
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TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT TUE JUL 21 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE ENTERING THE EASTERN CARIBBEAN SEA IS PRODUCING
DISORGANIZED SHOWERS AND THUNDERSTORMS. UPPER-LEVEL WINDS ARE
EXPECTED TO REMAIN UNFAVORABLE FOR DEVELOPMENT OF THIS SYSTEM FOR
THE NEXT COUPLE OF DAYS. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY
RAINFALL AND GUSTY WINDS WILL AFFECT PORTIONS OF THE LESSER ANTILLES
TODAY 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 KIMBERLAIN/PASCH
Quoting tennisgirl08:
Poll for rest of July:

1) no named storm
2) 1 named storm
3) 2 named storms
4) more frustrating invests!!!

LOL

(2), while (4) is another possibility
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Quoting tennisgirl08:
Poll for rest of July:

1) no named storm
2) 1 named storm
3) 2 named storms
4) more frustrating invests!!!

LOL


I go with 4! I want the NHC to do away with letting the public know about invests and just let us know once a TD has formed.
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Quoting tennisgirl08:


Yes, and looks to be going more WNW or NW now!

It started wnw earlier this morning
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2322. CUBWF
I go w/ 2. One may form in the coming days from all that mess around the bahamas
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Quoting CUBWF:
So, now may be under higher sheer and looks like it's going fast. Thank you tennisgirl


Yes, and looks to be going more WNW or NW now!
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Go to hit the sack - hope Shear continues to shred 97L and I can then wake up to a less potentially worriesome horizon - at least for the time being
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2319. CUBWF
I noted that frostyn
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Poll for rest of July:

1) no named storm
2) 1 named storm
3) 2 named storms
4) more frustrating invests!!!

LOL
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2317. CUBWF
So, now may be under higher sheer and looks like it's going fast. Thank you tennisgirl
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Quoting CUBWF:
Good evening everyone. Could be lcc of 97L located farther west at 14.9 and 64 w? Thanks in advanced


Yep, just a naked swirl.
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2315. CUBWF
Good evening everyone. Could be lcc of 97L located farther west at 14.9 and 64 w? Thanks in advanced
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Quoting cchsweatherman:
Think I'm finally going to surrender hope on Invest 97L now as wind shear has clearly won the battle as evident by the low-level circulation becoming well removed from the convection and moving at a good pace towards the WNW. You can clearly see it in the image below.


Figure 1 - Latest Nighttime Visible Image for Invest 97L
(Source: Tropical RAMSDIS Online)


Even though I no longer think it will develop, I'll still keep an eye on it just in case it pulls a surprise and proves me wrong.
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Quoting tennisgirl08:


Yeah, I see it, too. Just a naked swirl with all the convection to the east of the swirl. Will they deactivate the invest? I would be very surprised if they continued with this.


Most likely it will be deactivated later today.
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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.