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

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

Share this Blog
1
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1115 - 1065

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog Index

Quoting wunderkidcayman:

I agree
Do you agree with every comment that sounds like a developing storm and disagree with every comment that sounds negative to you ?
Member Since: October 9, 2008 Posts: 0 Comments: 8436
Quoting beell:
Glad we got that straightened out, homeless!

True on the roots-can you imagine if we got a bunch of rain and wind together? The trees would just tip right over. Think I'll go take a good look at my chainsaw-forgot to add this to the storm-prep list!


We did some extreme hurricane prep this March. Took down the last looming monster in the back yard. There are also a lot of dead trees from the salt water last fall. We got some pretty high winds yesterday. Hoping no repeat today.

STORM TOTAL RAINFALL WAS GENERALLY AROUND 2 INCHES ALONG THE
INTERSTATE 10 CORRIDOR AND SOUTH...WITH POCKETS APPROACHING 6
INCHES. 40 MPH GUSTS WERE COMMON AND RATHER LONG-LIVED...WITH
ISOLATED AREAS 60 PLUS. MUST SAY THAT THIS COMPLEX PRODUCED SOME
IMPRESSIVE AMOUNTS OF CLOUD TO GROUND AND LIGHTNING. ATTEMPTED TO
STICK MY HEAD OUT THE FRONT DOOR FOR A PEAK...BUT RAPIDLY RETURNED
INSIDE AFTER A NEARBY STRIKE. DID ALSO SEE CONSIDERABLE LIGHTNING
ACTIVITY IN POST-STRATOFORM RAINS...ALWAYS INTERESTING BUT NOT UNUSUAL
WITH THESE TYPE COMPLEXES.

Member Since: Posts: Comments:

AOI

AOI

AOI
Member Since: Posts: Comments:
Quoting stormpetrol:
I have the possible COC at 12.2N/53W., though convection is waning to me its looking more & more organized.

I agree
Member Since: June 13, 2009 Posts: 2 Comments: 12716
1111. Drakoen
Supports the development of a LLC:
Member Since: Posts: Comments:
I think 97L will start encountering shear over 20knts starting late tonight.Models take this more of a NW motion now instead of westward.So that means it will start seeing shear a little earlier now.Maybe it will be a TD in the last minute then break up.P.S.-BAMS model really likes to take the storm towards Florida everytime lol.If you look at it it takes it right off the Palm beach county coast and then turns away.
Member Since: Posts: Comments:
Quoting StormFreakyisher:
I know what happens during DMAX but what happens during D-MIN?


Your seeing it right now

Member Since: March 19, 2009 Posts: 0 Comments: 1421
Quoting TerraNova:
According to the GFS, shear in the E Caribbean should fall to marginally favorable levels through Tuesday but remain relatively unfavorable south and west of Cuba through Friday.

12z GFS shear forecast for 12z Wednesday July 22...

Link to full loop.


Does anyone believe the NOGAPS take on shear
Member Since: May 16, 2009 Posts: 1 Comments: 1231
The gfs is about as reliable as my EX. that aint good!!
Member Since: Posts: Comments:
Quoting StormFreakyisher:
I know what happens during DMAX but what happens during D-MIN?


convection decreases

there is much more to it than that but thats the overall effect of it on tropical waves..
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Link shear clearly weakens.
1104. beell
Even without the trough-looks what's coming right behind it down the side of the ridge following the trough.

WV Loop
Member Since: Posts: Comments:
I have the possible COC at 12.2N/53W., though convection is waning to me its looking more & more organized.
Member Since: Posts: Comments:
According to the GFS, shear in the E Caribbean should fall to marginally favorable levels through Tuesday but remain relatively unfavorable south and west of Cuba through Friday.

12z GFS shear forecast for 12z Wednesday July 22...

Link to full loop.

Member Since: July 30, 2007 Posts: 76 Comments: 4063
The NHC knows what its doing! It is looking over the next 48 hours,not just right now. overall windshear is not good for developement. It is going to have to slide in south of the trough. If it goes any farther north it will be beat up like it went 5 rounds with rocky and will probably knock it out!Now i know people on here are getting excited but this 97L has a gauntlet to go thru and then it has another one to go thru when it heads to the gulf and possible fl.MORE WINDSHEAR!! Thank GOD
Member Since: Posts: Comments:
Quoting Grothar:
I wanted to wait until all the multi-lingual bantering had ceded until I asked this question. I speak five languages and it was quite reminiscent of a U.N. delegation debate. My question: Has anyone a comment on the blob (I hope that is the correct word)that has moved off of the African Coast. Is there any potential for development. I know the current concern is for 97L. Just thought I would ask, premature as it may seem.



Just noticed that "blob" on the satellite.

Member Since: Posts: Comments:
lack of persistence again, this wont be a TD anytime soon
I know what happens during DMAX but what happens during D-MIN?
Member Since: Posts: Comments:
Quoting BurnedAfterPosting:
and the blog slows down with the realization that the shear may just be impacting 97L, therefore lowering its chances of development

either that or everyone left to eat dinner LOL


Must be dinner. I don't see shear impactiny anything yet with 97L. Windfield seems to be expanding, more convective bursts and generally better orgnized in general.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
1095. K8eCane
Quoting JLPR:
raining decently hard here in Carolina, PR
TW action xD


you mean there is a carolina there too??
nervously says oh dear wheres press?
Member Since: April 26, 2006 Posts: 5 Comments: 3222
1094. beell
Glad we got that straightened out, homeless!

True on the roots-can you imagine if we got a bunch of rain and wind together? The trees would just tip right over. Think I'll go take a good look at my chainsaw-forgot to add this to the storm-prep list!
Member Since: Posts: Comments:
1093. Drakoen
Quoting BurnedAfterPosting:
and the blog slows down with the realization that the shear may just be impacting 97L, therefore lowering its chances of development

either that or everyone left to eat dinner LOL


I'm not talking about now I'm talking 12-16 hours from now.
Member Since: Posts: Comments:
Quoting moonlightcowboy:
Sometimes, it's best to just drop the models and some of the charts, etc, and just use good, common sense with one's eyes. 97L is looking much more organized. There's no shear to speak of for a long time yet. At the rate it's improving, and through to Dmax, it could easily improve to TD status.

MLC , I agree with you 100%.
Member Since: Posts: Comments:
Yet another svere storm rolling through southern Palm beach county today.Taken near Town Center Mall at Boca Raton.


Member Since: Posts: Comments:
1090. Drakoen
Quoting moonlightcowboy:

Drak, I must not be seing what you're talking about here. To me it looked like the trough was oriented swest to neast and looks to lifting quite good. Meridionally - if you mean over the cCaribbean, I see that, but that's the tail of it and several 100 miles west yet and becoming more dispersed. Please, explain further. Thanks.


Meridional orientation just means it's elongated from north to south is some direction, opposite of zonal. The trough itself it titled.
Member Since: Posts: Comments:
That upper trough should begin to weaken tomorrow in the morning around 5 to 6utc.The gfs shear forcast is 2times stronger than i think it will be.
Starting to really feel the DMIN.

Member Since: June 9, 2007 Posts: 4 Comments: 15950
and the blog slows down with the realization that the shear may just be impacting 97L, therefore lowering its chances of development

either that or everyone left to eat dinner LOL
1086. Grothar
I wanted to wait until all the multi-lingual bantering had ceded until I asked this question. I speak five languages and it was quite reminiscent of a U.N. delegation debate. My question: Has anyone a comment on the blob (I hope that is the correct word)that has moved off of the African Coast. Is there any potential for development. I know the current concern is for 97L. Just thought I would ask, premature as it may seem.
Member Since: Posts: Comments:
1085. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 178 Comments: 56021
Quoting Drakoen:
The upper trough is too meridionally oriented. Not lifting out fast enough. I would say the system is only 350 miles from the trough.

Drak, I must not be seing what you're talking about here. To me it looked like the trough was oriented swest to neast and looks to lifting quite good. Meridionally - if you mean over the cCaribbean, I see that, but that's the tail of it and several 100 miles west yet and becoming more dispersed. Please, explain further. Thanks.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Quoting beell:


Talkin about the tree roots coming up above the ground level cause the soil around here has been subsiding-sorry.


Ooooh! Okay. Just call me Stu. Lol. I thought you meant the joke I laughed at wasn't your idea. My bad. And yes the soil subsiding is bad. All joking aside the tree roots lifting up to the surface is a bad thing this time of year. Rita took full advantage of that in 2005. Hopefully some of this rain will make it over your way. Not the severe stuff. Just the rain.
Member Since: Posts: Comments:
1082. JLPR
raining decently hard here in Carolina, PR
TW action xD
Member Since: Posts: Comments:
1081. Drakoen
The upper trough is too meridionally oriented. Not lifting out fast enough. I would say the system is only 350 miles from the trough.
Member Since: Posts: Comments:
Quoting Drakoen:


Or the 00z BAMM


00z BAMs will use 18z GFS for data.
Member Since: September 23, 2005 Posts: 15 Comments: 11342
At least through this night i give it a high chance of not being effected by wind shear.Moving through 5kt/than eighter 5 or 10kt.That should not be a prob tonight.
Quoting Drakoen:


Or the 00z BAMM


Even better.
Member Since: June 9, 2007 Posts: 4 Comments: 15950
1077. Drakoen
That upper trough still look potent and you can see on water vapor imagery how the moisture out ahead of 97L is starting to lift up to the northeast.
Member Since: Posts: Comments:
97l looks really good for only having a 30% or less chance of forming.I can't believe nhc has these probs.
Quoting HaboobsRsweet:
NOGAPS was built for over the water forecasting...how is that doing or did that model go away as well?

It predicts very favorable shear
Member Since: May 16, 2009 Posts: 1 Comments: 1231
You have to learn to use your "ignore" button.
every year in June, I start with a clean slate.. just in 24 hours already have been reminded why I put some of these bloggers on there last year and again this year...even when they change their handles..

Member Since: Posts: Comments:
Quoting TheWeatherMan504:


There was a Wind Gust to 70MPH at the Fort Pierce Airport.


The wind has been really bad here too the last half hour; its starting to subside but still gusts in the 30-40 mph range for sure.

I'll try and post some pics later showing the encroaching outflow boundary.

Gotta love south Florida weather!
Member Since: Posts: Comments:
Quoting TheWeatherMan504:


There was a Wind Gust to 70MPH at the Fort Pierce Airport.


The storms seem to be worst up north, but I have never seen winds that strong since Fay.
Member Since: July 19, 2008 Posts: 43 Comments: 4051
1071. Drakoen
Quoting Stormchaser2007:
I'd wait for the 00Z GFS to really start declaring lower shear in its path.


Or the 00z BAMM
Member Since: Posts: Comments:
NOGAPS was built for over the water forecasting...how is that doing or did that model go away as well?
Member Since: Posts: Comments:
Quoting Stormchaser2007:
I'd wait for the 00Z GFS to really start declaring lower shear in its path.


I agree with this.
Member Since: Posts: Comments:
Sometimes, it's best to just drop the models and some of the charts, etc, and just use good, common sense with one's eyes. 97L is looking much more organized. There's no shear to speak of for a long time yet. At the rate it's improving, and through to Dmax, it could easily improve to TD status.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Quoting TheWeatherMan504:


There was a Wind Gust to 70MPH at the Fort Pierce Airport.


Hm pretty impressive.
Member Since: June 9, 2007 Posts: 4 Comments: 15950
Quoting Funkadelic:


Very symetrical looking system in that photo.. D-MAX will produce Anna possibly?


No DMAX, will help generate more thunderstorms, creating a more predominant CDO, so that a sufficiently closed center may start to establish.
Member Since: July 19, 2008 Posts: 43 Comments: 4051
1065. beell
Quoting homelesswanderer:


UMMM? Sorry that one went over my head? Just tried to lighten things up. I'll go back to my lurk.


Talkin about the tree roots coming up above the ground level cause the soil around here has been subsiding-sorry.
Member Since: Posts: Comments:

Viewing: 1115 - 1065

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog Index

Top of Page

About

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

Local Weather

Overcast
27 °F
Overcast

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron