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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lol It would be discreet if NHC ever say "WE JUST DON'T KNOW!"
Member Since: Posts: Comments:
Quoting Drakoen:
Pasch is on duty; I like Pasch.

I like him too. He's been mainly noticeably absent this season. Most of the TWO's have been issued by a bunch of scrubeeneey's. Maybe his return signals something is up.
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1561. beell
Some of ya'll consider this inconsistent or confusing? Extending the period of unfavorable conditions from "tonight" out to 48 hrs? Stating these conditions will begin "tonight"?

Give 'em a break!

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM OVER THE
NEXT 24 TO 48 HOURS.

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM LATER TONIGHT.
Member Since: September 11, 2007 Posts: 144 Comments: 16768
1560. WxLogic
Quoting Drakoen:
It dropped 1 mb lol


Awesome... hey at least it has the fighting spirit...
Member Since: August 14, 2008 Posts: 4 Comments: 4978
Quoting nrtiwlnvragn:
AL 97 2009072000 BEST 0 125N 538W 25 1011 DB

Pressure dropped another millibar
Member Since: May 16, 2009 Posts: 1 Comments: 1231
1558. SLU
Quoting BurnedAfterPosting:


Might have to do with the latest GFS shear model showing shear more favorable than it did in previous runs


interesting ...
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1557. Drakoen
It dropped 1 mb lol
Member Since: October 28, 2006 Posts: 57 Comments: 30578
Quoting futuremet:


Viewer Discretion is advised.... You are about to witness the goring illustration of a beheaded tropical cyclone.



Wow!
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1554. Drakoen
Quoting beell:
That is a cool loop, futuremet. Glad someone has it stored.

Most of us just say "shear" and leave out references to tyrants of the French Revolution.



lol yea. I'm pretty sure Wikipedia has that stored.
Member Since: October 28, 2006 Posts: 57 Comments: 30578
thanks StormW...
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AL 97 2009072000 BEST 0 125N 538W 25 1011 DB
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Quoting Drakoen:
97L may be crossing the Rubicon to meet it's Waterloo.


Anyone for Beef Wellington?
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1550. bjdsrq
Looked like a hurricane that hit Siesta Beach today around 3:45pm. I saw the bow echo and knew the incoming squalls were going to have some kicking winds so I grab my gear and headed to the beach. Here's the video:
Siesta Beach Wind Storm - July 19, 2009

Member Since: Posts: Comments:
Hi folks, I hope you are all having a nice night. I just wanted to say please have a plan, and stay safe!

No one really knows when one of these "critters" may surprise you!

I wont call 97L dead untill it is gone. I watch closely!

Some of you here offer very good info that helps people learn. Thanks!
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1548. beell
That is a cool loop, futuremet. Glad someone has it stored.

Most of us just say "shear" and leave out references to tyrants of the French Revolution.

Member Since: September 11, 2007 Posts: 144 Comments: 16768
1542. HurricaneSwirl 12:20 AM GMT on July 20, 2009
Quoting Weather456:
lol I can't remember the blog being this funny, and the NHC being this inconsistent.97L is one for the books. Every time the GFS changes we get a change in the TWO:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM OVER THE
NEXT 24 TO 48 HOURS.


previously it was:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM LATER TONIGHT.




ill bet if they said 24-48 hours previously when it looked good, they would have upped it to code orange.

they are much more inconsistent, dependent among other sources, and conservative this year than any other it seems.


probably because the Gov't has taken over how and when to respond to storms now, hell why not they are taken over everything else...so if it's like the tele-promptors that keep malfunctioning or when Bieden pops off about something he shouldn't have said...we might never know if or when they will decide to inform us...lol..

just a ponder...
Member Since: Posts: Comments:
Quoting Drakoen:
97L may be crossing the Rubicon to meet it's Waterloo.


In other words SPLAT!! lol
1545. Drakoen
97L may be crossing the Rubicon to meet it's Waterloo.
Member Since: October 28, 2006 Posts: 57 Comments: 30578
Quoting beell:



Ok, I gotta hear more about this one...


Viewer Discretion is advised.... You are about to witness the goring illustration of a beheaded tropical cyclone.



Image credits to Cyberteddy
Member Since: Posts: Comments:
Quoting Weather456:
lol I can't remember the blog being this funny, and the NHC being this inconsistent.97L is one for the books. Every time the GFS changes we get a change in the TWO:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM OVER THE
NEXT 24 TO 48 HOURS.


previously it was:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM LATER TONIGHT.



ill bet if they said 24-48 hours previously when it looked good, they would have upped it to code orange.

they are much more inconsistent, dependent among other sources, and conservative this year than any other it seems.
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1541. 0741
storm w what your feelingt about 97l and shear???
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1540. Patrap
I'll be here...press


I suffered from the "Peppermint Schnapps effect" once.

Was a lotta spin to it too.

Member Since: July 3, 2005 Posts: 426 Comments: 128875
Quoting Weather456:
lol I can't remember the blog being this funny, and the NHC being this inconsistent.97L is one for the books. Every time the GFS changes we get a change in the TWO:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM OVER THE
NEXT 24 TO 48 HOURS.


previously it was:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM LATER TONIGHT.




No wonder we (the ones who are in learning mode) can't keep up and get confused. They seem to be confused too lol.
Member Since: Posts: Comments:
97L has a decent structure and could become a tropical depression if it has a good explosion of convection during d-max. I have no idea why people are saying this thing is dead. It probably has a llc and its the best we've seen this year. There is also a nice tropical wave further east in the Atlantic that looks promising.
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perfect Pat...Thanks...up and about some..will track you down this week...
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Quoting StormW:


Not tonight...just monitoring. I generally as a rule don't post on the weekends, especially Sunday, unless we have something going on or an immediate threat to the Islands or CONUS.


my bad...will sure remember....

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Member Since: Posts: Comments:
Quoting Drakoen:


Water vapor imagery shows 97L is nearing the periphery of the open upper level ridge that has been protecting it. An anticyclone cannot protect a system from an advancing upper level trough.
thanks drak looks like we have some works of art with us tonight if you know what i mean !
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Quoting IKE:


Exactly. Just the same stuff over and over and over.

Jeez...go take a walk...mow the yard...play with your kids...


Going to watch the ESPY's :)
Member Since: July 7, 2005 Posts: 0 Comments: 5364
1532. beell
Quoting futuremet:
...which is mostly unfavorable, but not so unfavorable to induce a Robespierre effect. Once it passes through the Lesser Antilles, then it will have to be watch for development, as the TUTT rapidly lifts and replaced with the STR, producing ventilation for tropical cyclogenesis.



Ok, I gotta hear more about this one...
Member Since: September 11, 2007 Posts: 144 Comments: 16768
1531. Patrap
Nada,,zip...

with scattered Heat..

dat bout it press
Member Since: July 3, 2005 Posts: 426 Comments: 128875
1530. Patrap
Well sport,synoptic changes occur thru time and the scenarios change.

Its called weather for a reason
Member Since: July 3, 2005 Posts: 426 Comments: 128875
1529. Drakoen
Quoting Seflhurricane:
drak what d you think is the trough going to inflict significant damage to 97L


Water vapor imagery shows 97L is nearing the periphery of the open upper level ridge that has been protecting it. An anticyclone cannot protect a system from an advancing upper level trough.
Member Since: October 28, 2006 Posts: 57 Comments: 30578
been at da beach...

Would one of you experts be so kind as to give me a quick update on the near term tropical weather outlook? And remember: please keep it no more complex than about a third grade level...
Member Since: Posts: Comments:
Quoting StormW:


Not tonight...just monitoring. I generally as a rule don't post on the weekends, especially Sunday, unless we have something going on or an immediate threat to the Islands or CONUS.
Thanks for all you do storm
Member Since: Posts: Comments:
lol I can't remember the blog being this funny, and the NHC being this inconsistent.97L is one for the books. Every time the GFS changes we get a change in the TWO:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM OVER THE
NEXT 24 TO 48 HOURS.


previously it was:

UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM LATER TONIGHT.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
I KNOW (sorry for caps, Its just so people can see the message out of all the others) a lot of people have been asking about DMIN and DMAX bug this one is different. Does DMAX and DMIN have an effect over land, meaning do storms spark up at or just before sunrise and diminish before sunset, it doesn't that it happens over land like that but it's interesting. THANK YOU
Member Since: Posts: Comments:
Quoting Drakoen:
Closing in on the upper trough:
drak what d you think is the trough going to inflict significant damage to 97L
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1523. Patrap
Not much meat on dem bones this evening...

JSC ch.
Member Since: July 3, 2005 Posts: 426 Comments: 128875
Quoting futuremet:
This what will likely happen:

Substantial thunderstorm activity will increase tonight, and this might help form a central dense overcast (CDO), which would support the formation of a sufficiently closed LLC. Nevertheless, wind shear should not adequately slacken in time for significant coalescence, because mean shear should approximately be 20kts, which is mostly unfavorable, but not so unfavorable to induce a Robespierre effect. Once it passes through the Lesser Antilles, then it will have to be watch for development, as the TUTT rapidly lifts and replaced with the STR, producing ventilation for tropical cyclogenesis.


Seems rather reasonable. Only time will tell.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
Quoting Funkadelic:


OMG, today I was in a weather chat with Mr.Eddye over here and he was like "This is going to be floridas storm, I spoke with Brian Norcross of nbc and he says its headed right for Florida"

Lol hes a character I will tell you that much


Hes a liar and a troll. You really should ignore him.
Member Since: June 9, 2007 Posts: 4 Comments: 15923
1518. Drakoen
Closing in on the upper trough:
Member Since: October 28, 2006 Posts: 57 Comments: 30578
Quoting hurricane23:
18z HWRF shows nothing.


HWRF showed 94L becoming a CAT3 hitting FL, so I don't know what makes it so special now lol
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Quoting CybrTeddy:
If they were able to declare Tropical Storm Nana last year before it was ripped apart, if 97L becomes much better organized overnight, they wont have an excuse not to name it a TD tomorrow or Tuesday (likely tuesday)
thats my thinking they are probably going to wait and see what the windshear is going to do to it tomorrow
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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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