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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Who was it that showed us that wind storm on the beach in Florida yesterday? I just saw that same video on the weather channel.
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Quoting nrtiwlnvragn:
Interesting views of 97L from Windsat. No time stamp on those images, but the scat time stamp is 0946.

It is very interesting
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Interesting views of 97L from Windsat. No time stamp on those images, but the scat time stamp is 0946.
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How do they produce the 'future' shear maps? Are they computer models such as the computer models for when storms do form? I guess my real question is, how accurate are the models for future shear? Is there some statistical data similar to what can be found for tropical storm models?
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Quoting stormsurge39:
Does anybody else see that the shear maps are not matching what it looks like on the satt? Am i the only crazy one here?


Shear is easily 30-35kts.......maybe this loop will help you!
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting weatherwatcher12:

What do you think about the westerlies in Trinidad


I have been looking south of the system and you can see low level clouds veering SW:
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341. stormsurge

New maps should be out soon. CIMSS are from over four hours ago... and it did look different then.
Member Since: September 9, 2008 Posts: 6 Comments: 3414
Quoting stormsurge39:
Does anybody else see that the shear maps are not matching what it looks like on the satt? Am i the only crazy one here?

It's updating in 18 mins
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting KEEPEROFTHEGATE:
YOU SHOULD NOT BE DOING THAT AT A TIME LIKE THIS IT IS NOT RIGHT


sheeeshh. i get the point already >.>

not right? I stated before my post "this will never happen" and i stated after my post "nothing against the cayman islands" and "nothing against the nhc". but i see you posted around the same time that i did
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Does anybody else see that the shear maps are not matching what it looks like on the satt? Am i the only crazy one here?
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Quoting weatherwatcher12:

What do you think about the westerlies in Trinidad

Also a westerly reported in Martinique
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting KEEPEROFTHEGATE:
YOU SHOULD NOT BE DOING THAT AT A TIME LIKE THIS IT IS NOT RIGHT


lol, rage.
chill man, he just apologized.
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If 97l surves it will go northwest to near cuba/than southwest to mexico or western gulf.
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Quoting Drakoen:
Radar, surface observations, and 850mb vort maxima would indicate a low pressure center over eastern Barbados which would coincide more with shear affecting the system. For some reason I can't believe the position the 12z BAMM guidance initiation has put it.

What do you think about the westerlies in Trinidad
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting HurricaneSwirl:


Ok I know this would never happen but would it be hilarious of the NHC said this?

..AN UNUSUALLY LOW PRESSURE OF 965 MB WAS OBSERVED IN A POCKET OF DRY AIR AT THE CENTER OF A FEW SHOWERS IN THE NORTHWEST CARIBBEAN SEA. HOWEVER DUE TO PROXIMITY TO THE CAYMAN ISLANDS THERE IS A LOW CHANCE...LESS THAN 30 PERCENT... OF THIS SYSTEM BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HOURS.

nothing against the caymans.. i was just trying to find the smallest islands in an area of the highest heat potential.. nothing against the nhc either, ive agreed with the majority of their forecasts, but i would laugh so hard if i saw that in their tropical outlook.
YOU SHOULD NOT BE DOING THAT AT A TIME LIKE THIS IT IS NOT RIGHT
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Quoting Drakoen:


Don't make fake advisories. Or Jeff Masters will be knocking on your door.


K. admins must be coming down hard now that its the season.
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Radar, surface observations, and 850mb vort maxima would indicate a low pressure center over eastern Barbados which would coincide more with shear affecting the system. For some reason I can't believe the position the 12z BAMM guidance initiation has put it.
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Night Aussie!
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Quoting stormsurge39:
I agree canes!!! these downplayers all over the weather news are not using thier eyes right now. It doesnt look like anything is effecting it. wheres all this fierce shear? The father west it goes its going to suck up bath water and explode!!!!!!!!!!!!!
remember shear does not affect tropical waves shear affects the low and if there is no low of course there is absolutely no TD i put a rather high chance of development because as it moves quickly along shear will lift over Haiti.
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Quoting Ossqss:


Where are you seeing that?


When I would hit refresh it would pop up. It isn't doing it anymore.
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Goodnight all.
Goodnight alaina1085
No fighting please kids.
Happy 40th Anniversary of the 1969 Apollo 11
Moon landing.

Stay safe, God Bless
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This storm has enough divergence and warm ssts to survive.Starting by mid afternoon tomorrow it will have 10kt shear.That will even drop to 5kt tomorrow night.Today it will have 20 to 40kt shear to contend with.
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Quoting StormW:
Good afternoon!

TROPICAL WEATHER SYNOPSIS JULY 20, 2009 ISSUED 12:00 NOON EDT


Nice analysis StormW! Thanks so much!
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Developing system or not, I learn either way from all of you.
Sometimes the whys of a system that does not develop, offer the best lessons.
Thank you

Out of here - my more immediate world beckons.
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Thanks Storm, good update as usual. Guess we just wait and see what 97L has in store.
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I agree canes!!! these downplayers all over the weather news are not using thier eyes right now. It doesnt look like anything is effecting it. wheres all this fierce shear? The father west it goes its going to suck up bath water and explode!!!!!!!!!!!!!
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Quoting HurricaneSwirl:


Ok I know this would never happen but would it be hilarious of the NHC said this?

..AN UNUSUALLY LOW PRESSURE OF 965 MB WAS OBSERVED IN A POCKET OF DRY AIR AT THE CENTER OF A FEW SHOWERS IN THE NORTHWEST CARIBBEAN SEA. HOWEVER DUE TO PROXIMITY TO THE CAYMAN ISLANDS THERE IS A LOW CHANCE...LESS THAN 30 PERCENT... OF THIS SYSTEM BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HOURS.

nothing against the caymans.. i was just trying to find the smallest islands in an area of the highest heat potential.. nothing against the nhc either, ive agreed with the majority of their forecasts, but i would laugh so hard if i saw that in their tropical outlook.


Don't make fake advisories. Or Jeff Masters will be knocking on your door.
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Quoting canesrule1:
My 48 hour formation potential is 30-50%, formation potential in general 50+%, thoughts, post if you agree or disagree.


Zero chance in 48hrs........a larger chance thereafter if it can stay together
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Thanks for the update Storm!
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-
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Shear is hitting 97L from 2 directions.....from the West and from the South. The further south it stays the better chance circulation might stay in tack.....MIGHT! Shear of 40-50kts is coming just to the West of 97L in 12 or less hrs. It will be ripped IMO!
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting StormW:
Good afternoon!

TROPICAL WEATHER SYNOPSIS JULY 20, 2009 ISSUED 12:00 NOON EDT

Thanks for the update.
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One thing is, considering its willpower, how far would this be along if it didn't have so much shear to contend with?
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Quoting SomeRandomTexan:
That is some pretty heavy covection in 97L... If the ULL can move out quicker and allow that trof to lift things could get a bit more interesting... I'm really surpised she is doing this well! :)

The ULL is moving at a good clip.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
That is some pretty heavy covection in 97L... If the ULL can move out quicker and allow that trof to lift things could get a bit more interesting... I'm really surpised she is doing this well! :)
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She's is for sure a female. Because she's stubborn and refuses to let go.
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Sorry about that all....

Tortola, British Virgin Islands WeatherCam
Link

To gain access
enter "public" as username & "weather" as password
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2 inches of rain so far today. Wind out of the SW very light.
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Quoting RitaEvac:
She's trying to stay south of the 15w Lattitude, she's going for the dive into the end zone, when she scores, it's game over for NHC, they will have to recognize her


ROFL...
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Quoting BurnedAfterPosting:


take the Z off the end right before the .GIF, that is the map I am using
I thought the Z map is just a closer look.
Both are labeled:
GOES EAST Wind Shear(Kts)1200 UTC UW-CIMSS/NESDIS
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My 48 hour formation potential is 30-50%, formation potential in general 50+%, thoughts, post if you agree or disagree.
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Brennan is on duty today...
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Quoting CaneWarning:


I got that too.


Where are you seeing that?
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Quoting TerraNova:


Overlay was generated at 09z when the COC was in that position. It's since moved further west and is somewhere near Barbados, at least that's what I'd say based on satellite loops and radar.


Ok that makes sence.......I agree!
Member Since: September 2, 2007 Posts: 178 Comments: 20439
She's trying to stay south of the 15w Lattitude, she's going for the dive into the end zone, when she scores, it's game over for NHC, they will have to recognize her
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LATEST 1156 AM EDT
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Quoting weatherwatcher12:
Is it me or is th ULL moving away:

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