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 Vortex95:
Guys Drak is pulling your leg


How?? No one is near me right now.
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Quoting IKE:


No potential?

Here's what Dr. Master said...

"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."


Conditions are just fine were the disturbance is presently which (may) allow for this to reach TD intensity BUT the issue is what lies ahead the southerly jet is very much entrenched down there take a look at THIS MAP 50kt shear all over the caribbean this thing will suffer the same fate of the previous wave.This is what el nino will do for you.The islands could see some squally weather.
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Quoting beell:
Little bit of turning at the northern end of the wave that preceeded 97L. 26N 62W
Yeah, I posted that earlier, not sure what to make of it
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Quoting Stormchaser2007:
Doesnt look like the TUTTs going to lift in time. Ah well...


ah well as in RIP?

Again writing it off too quickly, makes you lose all credibility
According to the NHC we should be preparing 97L's requiem.
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I like sarcasm and jolking around, but a word of caution to thoses mimicking NHC content. The FEDS have been known to make mountains out of molehills.

NHC Disclaimer

The information on government servers are in the public domain, unless specifically annotated otherwise, and may be used freely by the public so long as you do not 1) claim it is your own (e.g. by claiming copyright for NWS information -- see below), 2) use it in a manner that implies an endorsement or affiliation with NOAA/NWS, or 3) modify it in content and then present it as official government material. You also cannot present information of your own in a way that makes it appear to be official government information..
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Yall have no idea what the NHC is thinking. They are saying really the same thing that Dr. Masters is saying. Yall just need to wait and watch.
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407. beell
Little bit of turning at the northern end of the wave that preceeded 97L. 26N 62W
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It is obvious that the pending conditions that are expected to increase shear by tonight is the main reason behind the NHC staying at 30%

If the shear forecast changes and 97L continues to get better organized, you will see the NHC bump up the chances of development.
Doesnt look like the TUTTs going to lift in time. Ah well...
Member Since: June 9, 2007 Posts: 4 Comments: 15718
Well we all will know by 2night.
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The nogaps predicts shear lifting out of the Caribbean-

Member Since: May 16, 2009 Posts: 1 Comments: 1231
NHC always seems to be behind the curve when systems develope fast. Regardless, the eastern carrib will be its "trial by fire".Real tough for storms to develope there. If it survives the eastern carrib, watch out when it gets over to western carrib.
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Quoting IKE:


I'm talking about what he said about it's potential to the islands...not beyond there.

People do live on those islands. He said it could be a TD by then.


It may, but i guess the nhc and masters just have different opinions. even if it does make it it doesn't look like it'll be for very long. I'm sure the islands get Tstorms similar to TD's.
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Quoting WAHA:

NOR DO WE CARE?! That thing is exploding with development! They're playing it safe again!
That is my issue, it's not safe for the public.
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Quoting IKE:


I'm talking about what he said about it's potential to the islands...not beyond there.

People do live on those islands. He said it could be a TD by then.


Yep that was what I thinking as well, is Shear going to keep it from developing further between today and tomorrow according to the NHC it says tonight 97L will reach those conditions so we will see.
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Quoting IKE:


Is UNwatchable.



Agreed.
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One whole page of comments,..1 image..
LOL

Banter it to death,and It will go "Poof".


Gulf and Tropics (Updated every ~1/2 hour)
Member Since: July 3, 2005 Posts: 414 Comments: 125466
MLC, post 382.
Good post there.
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391. WAHA
Quoting Drakoen:
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 WITH A PIN HOLE EYE DEVELOPING. WHILE ENVIRONMENTAL
CONDITIONS ARE CURRENTLY FAVORABLE FOR SOME DEVELOPMENT OF THIS
SYSTEM TO BECOME A MAJOR HURRICANE...UPPER-LEVEL WINDS ARE EXPECTED TO BECOME LESS FAVORABLE
TONIGHT. REGARDLESS OF DEVELOPMENT WHICH WE THINK WILL NOT OCCUR NOR DO WE CARE...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 AN EXTEMELY LOW CHANCE...LESS THAN
30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

NOR DO WE CARE?! That thing is exploding with development! They're playing it safe again!
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Quoting CybrTeddy:
The longer we wait, the more likely Ana will be stronger.
Quoting HurricaneSwirl:


read the rest...

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.


Apples and oranges. You are talking about the W. Caribbean the other user is talking about the E. Caribbean.
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389. IKE
Quoting BaltOCane:
Tropical Update only mentioned it.

No radar images or anything, and the "weather lady" was standing right in front of it...

Ahh, the Sunday afternoon cast...


Is UNwatchable.

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388. IKE
Quoting HurricaneSwirl:


read the rest...

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.


I'm talking about what he said about it's potential to the islands...not beyond there.

People do live on those islands. He said it could be a TD by then.
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Quoting Patrap:
Slackers ?..do it yourself..LOL

or we could put it in a Pork Bill and you can post it on your blog.


You know how I roll. ;)

LOL
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Tropical Update only mentioned it.

No radar images or anything, and the "weather lady" was standing right in front of it...

Ahh, the Sunday afternoon cast...
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Quoting centex:
Ditto GR "Get Real"
1am real and i call it as i see it in last hour and 30 mins convective field has shunk and warmed by next image all the black is gone dont be fooled some here including the NHC know exactly what where doing
Member Since: July 15, 2006 Posts: 163 Comments: 52162
We all have a tendacy to stick with our forecast and NHC no exception. This can cause problems in future forecast if current data is weighted less. I see this all the time especialy when technical data is missing.
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Quoting hurricane23:


Theres really no potential here for this disturbance,Its only got a brief period to do something before it runs into 30-40kt shear.The digging trof of low pressure along the southeast should pull what ever is down there up the eastcoast were shear will be quite high ahead of our trof.Iam still holding on to no storms till august.


Respect, Adrian, but I have to disagree somewhat. There is no shear now, no substantial shear ahead, decreasing even - and nearly every level of steering keeps 97L in a westerly motion. The upper level trough is lifting or dissipating and those upper winds will have little effect at the sfc unless 97L really cranks up. And, even then, I believe that will only aid in venting as it continues to move mostly west into the eCaribbean and strengthens.

The CONUS trough will have to dig deep into the Caribbean to start effecting a substantial turn more northwards. I don't see that happening within the next day or two.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
Quoting IKE:


No potential?

Here's what Dr. Master said...

"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."


read the rest...

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.
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The longer we wait, the more likely Ana will be stronger.
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.
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Quoting hurricane23:


Theres really no potential here for this disturbance,Its only got a brief period to do something before it runs into 30-40kt shear.The digging trof of low pressure along the southeast should pull what ever is down there up the eastcoast were shear will be quite high ahead of our trof.Iam still holding on to no storms till august.


Which could be very true but will it hit that 30-40 knots shear before Barbados or not? If not the island could face some nasty weather.
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Id be preparing for those 25 mph winds in the islands if I were there.
Member Since: July 3, 2005 Posts: 414 Comments: 125466
At the end of the day.. yellow or orange.

It's not like it's going to be upgraded to a TD anytime soon. (Tomorrow at the very earliest)

If at all, we don't know.
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NHC says due to unfavorable upper level winds, possibility for deveopment of this system, though better organized, is still less than 30%.

Very conservative, as usual.
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373. IKE
Quoting hurricane23:


Theres really no potential here for this disturbance,Its only got a brief period to do something before it runs into 30-40kt shear.The digging trof of low pressure along the southeast should pull what ever is down there up the eastcoast were shear will be quite high ahead of our trof.Iam still holding on to no storms till august.


No potential?

Here's what Dr. Master said...

"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."
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97L should just dissipate.
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Slackers ?..do it yourself..LOL

or we could put it in a Pork Bill and you can post it on your blog.
Member Since: July 3, 2005 Posts: 414 Comments: 125466
Alright slackers. Can I get the TWO posted already? :0 It's OUT!
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369. IKE
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.


I have little sense in their reasoning.

TS Fay last year when it was clearly finally gone and the COC was within 12 miles of me, they still had listed as a 40 mph TS...and the winds at my house were about 10 mph.

Their slow on developing systems and slow on killing them.

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Quoting BurnedAfterPosting:


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


lol, well then i apologize. I honestly thought it should have been a code orange as well though, but the NHC is right about upper level winds becoming unfavorable as early as tonight.

and I have no clue if that "sarcasm is not an art that everyone can excel at" was directed at me, its a lot harder to make something sarcastic while typing, i dont like putting LOLOLOLOL at the end of all of my posts >.>
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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.


Theres really no potential here for this disturbance,Its only got a brief period to do something before it runs into 30-40kt shear.The digging trof of low pressure along the southeast should pull what ever is down there up the eastcoast were shear will be quite high ahead of our trof.Iam still holding on to no storms till august.
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If it was in the GOM under the same circumstances and the threatening the US Gulf Coast, it would have an orange circle. However, I'm waiting for tonight on Monday, for this "increase in upper winds" but being so close to the islands, I hope they know what they are doing.
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Quoting IKE:
convective tops warming

LOL

Ditto GR "Get Real"
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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.