97L growing more organized, will bring heavy rain to the Lesser Antilles

By: Dr. Jeff Masters , 3:55 PM GMT on July 19, 2009

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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

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Quoting IKE:
convective tops warming

LOL

Ditto GR "Get Real"
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What was the ol' rule of thumb about distance from the islands? Wasn't it 500 miles? Or 55 west?

It's getting close to that now.
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Quoting HurricaneSwirl:


You mean the post where I said "it had such good potential :("

isn't a guy allowed to be sarcastic sometimes


yea only if you make it seem sarcastic, many people took your post seriously

sarcasm is an art form that not everyone can excel at lol
Quoting CybrTeddy:
I give up with the NHC, they're been overly conservitive this year. Like Ike, I wave the white flag. Call me a wishcaster if you like, but how they handled systems like 90L (which WAS a Tropical Storm, it met all the requirments even in their book) and 92L. Well, I guess they are the experts. After all, I don't have a PhD on this.


No but we have eyes and 3+ years at Weather Underground...oh wait.
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Quoting WeatherStudent:
If lost of life occurs in the Carib because of this system, it's going to be on they're heads for not warning the public at all abotu this little critter. Bill Reeds, for the love of God, open up your eyes and see what's going on. I'm gonna have to pay them a visit at FIU. On second thought, I'll wait until I move into the University next month before doing so.


is that a threat?? better be careful how ya word things
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Quoting BurnedAfterPosting:


Chill out, you got so many responses because of how you posted. Go look at your post again and you will see why.


You mean the post where I said "it had such good potential :("

isn't a guy allowed to be sarcastic sometimes
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359. JRRP
another game ?
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I give up with the NHC, they're been overly conservitive this year. Like Ike, I wave the white flag. Call me a wishcaster if you like, but how they handled systems like 90L (which WAS a Tropical Storm, it met all the requirments even in their book) and 92L. Well, I guess they are the experts. After all, I don't have a PhD on this.
Member Since: July 8, 2005 Posts: 259 Comments: 24198
357. IKE
convective tops warming

LOL

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I guess they are waiting for tonight. The old persistance thing. What this does is tell all the mets not to worry. Not sure that is what they should be projecting. Granted they should not hype but how can you hype a developing TD?
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Quoting IKE:


Think it was 90L...yeah, they were classic on that one...scheduling a 100 mile recon flight for 6 hours after it made landfall.....

lol
Member Since: May 16, 2009 Posts: 1 Comments: 1231
25 mph winds in 97.

Hunker down..
Member Since: July 3, 2005 Posts: 426 Comments: 128751
Quoting Drakoen:


I thought that 91L was a minimal tropical storm when it made landfall. NHC is too conservative this season.


that was 90L but yeah I agree

also 92L was clearly subtropical
352. Nikko
Another Strong Thunderstorm warning on Broward County...

This year is very active in south Florida.

Yesterday we got hurricane conditions for 2 hours. Was a lot worse than Fay for example...

Link
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convective tops warming
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Quoting moonlightcowboy:


Yup, Ike, I felt that way with, what was it, 91L that made landfall near Mobile.


I thought that 91L was a minimal tropical storm when it made landfall. NHC is too conservative this season.
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More inconsistencies at the NHC. Whatever...they're the experts.
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Quoting HurricaneSwirl:
OMG. This blog has got to be one of the most ridiculous of blogs.

JUST because I disagree with you and say it wont develop I get bashed and called a drama maker. WTH? Aren't I allowed an opinion?

JRRP said it wouldn't develop
Taz did too.

But they don't get bashed? Why, is it because they're older and have been here longer?

I'm saying shear is just too high, as always with an El Nino year.

I know you guys want a storm but in my opinion this isn't it.
And we can write you off as you are writing IT off....El Nino blows both ways.
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Quoting hurricane23:
Again upper conditions lol do not favor any significant intensification.Clear signs of el nino when you look at the caribbean fast westerlies all across.NHC keeps it at yellow.


Thank you.
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345. IKE
Quoting moonlightcowboy:


Yup, Ike, I felt that way with, what was it, 91L that made landfall near Mobile.


Think it was 90L...yeah, they were classic on that one...scheduling a 100 mile recon flight for 6 hours after it made landfall.....
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Quoting HurricaneSwirl:
OMG. This blog has got to be one of the most ridiculous of blogs.

JUST because I disagree with you and say it wont develop I get bashed and called a drama maker. WTH? Aren't I allowed an opinion?

JRRP said it wouldn't develop
Taz did too.

But they don't get bashed? Why, is it because they're older and have been here longer?

I'm saying shear is just too high, as always with an El Nino year.

I know you guys want a storm but in my opinion this isn't it.


Chill out, you got so many responses because of how you posted. Go look at your post again and you will see why.
342. IKE
Quoting hunkerdown:
Maybe they are out of orange and red crayons. Budget cuts may have kept them from replenishing their supplies.


Apparently.
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Quoting IKE:


LMAO.....LMAO.....what does it take with these folks?

That is a yellow and that blob west of it that got killed was yellow?

I wave the white flag w/the NHC.


Yup, Ike, I felt that way with, what was it, 91L that made landfall near Mobile.
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Quoting IKE:


LMAO.....LMAO.....what does it take with these folks?

That is a yellow and that blob west of it that got killed was yellow?

I wave the white flag w/the NHC.


They did it for the lulz. Brennan and Blake aren't phased.
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339. JRRP
damn..... i was trying to use inverse psychology but .....
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A has it
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OMG. This blog has got to be one of the most ridiculous of blogs.

JUST because I disagree with you and say it wont develop I get bashed and called a drama maker. WTH? Aren't I allowed an opinion?

JRRP said it wouldn't develop
Taz did too.

But they don't get bashed? Why, is it because they're older and have been here longer?

I'm saying shear is just too high, as always with an El Nino year.

I know you guys want a storm but in my opinion this isn't it.
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well if conditions tonight aren't less favorable hmmm...
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Quoting Drakoen:


It's going to need to get that pinhole eye before they get it to orange.
Maybe they are out of orange and red crayons. Budget cuts may have kept them from replenishing their supplies.
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333. IKE
Quoting Drakoen:


It's going to need to get that pinhole eye before they get it to orange.


LMAO.....LMAO.....what does it take with these folks?

That is a yellow and that blob west of it that got killed was yellow?

I wave the white flag w/the NHC.
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Yellow??? I seriously thought they would go red, or at least orange.
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Again upper conditions lol do not favor any significant intensification.Clear signs of el nino when you look at the caribbean fast westerlies all across.NHC keeps it at yellow.
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Hmm.. Well shear is supposed to rise so maybe not TOO much of a surprise. Imagine 97L becomes a Depression right before the shear hits it and the NHC skips it lol. Only a low chance, but hey, stranger thing have happened.
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Quoting IKE:
Still yellow? Are you kidding me?

WTH?


Comebacks for the yellow circle Ike? lol :)
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Quoting Drakoen:
LOL the NHC went with A what a surprise.


What a shock.
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Convection is blowing up over the coc, turning becoming more evident, moving a bit slower, too, I think. I think 97L is stretching its legs, getting ready to show out a bit. Def, def, definitely orange. ;)
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Quoting IKE:
Still yellow? Are you kidding me?

WTH?


It's going to need to get that pinhole eye before they get it to orange.
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DDR lucky you !
I have been watching the rain fall on you ! LOL
Wish it would fall here, I would be able to finish some chopping of trees. Right now, it is just too damm hot to go out there...
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Quoting IKE:


That was a 59 yr-old choke job.

But not if old man outlast and wins playoff. That approach shot killed him.
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322. IKE
Still yellow? Are you kidding me?

WTH?
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321. JRRP
000
ABNT20 KNHC 191732
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SUN JUL 19 2009

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

SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE
LOCATED ABOUT 600 MILES EAST OF THE WINDWARD ISLANDS HAS BECOME
BETTER ORGANIZED OVER THE PAST SEVERAL HOURS. WHILE ENVIRONMENTAL
CONDITIONS ARE CURRENTLY FAVORABLE FOR SOME DEVELOPMENT OF THIS
SYSTEM...UPPER-LEVEL WINDS ARE EXPECTED TO BECOME LESS FAVORABLE
TONIGHT. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL AND
GUSTY WINDS COULD AFFECT THE WINDWARD ISLANDS ON MONDAY 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.
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Doesn't seem to me like the NHC think much of this.
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A Wins!!!


LOL the NHC went with A what a surprise.
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Quoting BurnedAfterPosting:


You are basing that on what?


many models. models arent always right but the fact is the shear is very high just to its north and just to its west. if it slows down it'll probably be ok, but at this speed there wont be enough time for shear to fall imo.


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Quoting IKE:


Nope...no rain...83 and partly sunny.


At least your not in the 90s like me lol.. I hate Florida.
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Quoting HurricaneSwirl:


Shear is supposed to be over 20 knots over this system for nearly the rest of its life.

And so what if i did look at a past one? Shear needed to fall earlier. And it didn't. If it doesn't fall by tonight this thing might get ripped apart.
What are you talking about ? It has many miles to transverse with plenty of time for shear to increase or decrease. And as far as its "lifetime" track, you know what that is going to be ? Please, enlighten us all, and of course, why...
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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.

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