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: 615 - 565

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

I will have to say that if it goes into the gulf it will go east towards central FL
Member Since: Posts: Comments:
The NHC does a Fantastic job when the Going gets tough..always.
A 25 mph Invest isnt a threat to Birds..

Lighten Up Francis and Francine..
Member Since: Posts: Comments:
Someone go to :http://www.nrlmry.navy.mil and look for the GEO Vapor satellite that is most recent. Shows something blowing up on the eastern edge of the storm
Member Since: Posts: Comments:
Quoting plywoodstatenative:
Keeper,

Notice where the system is and where the dry air has shifted to?
yes NHC made the right call
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Central convection looks to be deteriorating quickly. Do not say its due to DMIN. This is expected as the day goes on. Although it should regain convection tonight.
Member Since: Posts: Comments:
97L Early Track Guidance

Member Since: Posts: Comments:
the bashing is getting a bit old folks lol

Like I said I can see why they said what they said, it is based on the forecasted shear, those things can change

we will see how it plays out, but please lets cut the bashing
Quoting Vortex95:
Quickscat missing 97l may have had somthing to do with it as well. Man that thing is glitchy.


Nar, it's a polar orbiting satellite thus becuz of its rotation, it overlaps between 40N and 40S. Thus the blank swaths.
Member Since: Posts: Comments:
Quoting plywoodsale:


Too much NHC bashing going on here. They did say it was more organized but the 48 hour forecast calls for a date with the shear monster.....
soon to be replaced with empty space
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Keeper,

Notice where the system is and where the dry air has shifted to?
Member Since: Posts: Comments:
Quoting BurnedAfterPosting:
A Wins!!!




I won! I won!

NHC fails, though.
Member Since: Posts: Comments:


latest as of 301pm edt
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Quoting Drakoen:
97L did a great job of organizing today. Too bad that does nothing for the NHC.


Too much NHC bashing going on here. They did say it was more organized but the 48 hour forecast calls for a date with the shear monster.....
Member Since: Posts: Comments:
Looks like an anticyclone will be in the Central Caribbean. It will be very interesting to see if 97L can make it there.

Member Since: Posts: Comments:
I have been trying to get this to pop in, its the water vapor image from the Navy site. Shows that something is going on with the system.

Link
Member Since: Posts: Comments:
Quoting CUBWF:
Hi Drak, are there still the same conditions for high wind sheer in a couple of days northern Cuba.


Yes. The system need to get itself in the Central Caribbean where it would have a chance to become vertically stacked with an upper level high.
Member Since: Posts: Comments:
97L did a great job of organizing today. Too bad that does nothing for the NHC.
Member Since: Posts: Comments:
595. IKE
Cloud tops are cooling over my house where it's raining w/a thunderstorm....

Member Since: Posts: Comments:
This storm has been the hardest to figure out, it truly has a mind of its own and might be the one that will get the season going unfortunately.
Member Since: Posts: Comments:
Comming out of lurk status for a second. Been here for three years.

Allot of old time posters, respected posters it appears are saying that they are not agreeing with the NHC. So many so that it caught my attention. Is it just this one wave you guys don't agree with the NHC or in general your not happy with the NHC this year.
Member Since: Posts: Comments:
592. CUBWF
Hi Drak, are there still the same conditions for high wind sheer in a couple of days northern Cuba.
Member Since: Posts: Comments:
Quoting eddye:
weatherwatcher is it coming to fl

Right now it's too early to tell. It's sort of a wait and see situation.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting plywoodstatenative:
Here is an item for all to think about. We have had a stationary front over Northern Florida for the past month or so. If it were to get into the Gulf, what role would this front have in steering the system?


Plywoodsale, what then is your feeling on that?
Member Since: Posts: Comments:
DMAX may be very interesting later. Especially if it can hold some convection.
Member Since: Posts: Comments:
eddye, go to the tropics talk, want to bring something to you.
Member Since: Posts: Comments:
Quoting plywoodstatenative:
Drak, no clue who the other piece of driftwood is in here.

My concern is the winds and shear values in the Caribbean. So far this system has beaten everything that has been posted about it, high shear, dry air and the such. I am concerned that in the end, it won't be us eating the crow but instead it would be the NHC.


Meh...the nhc has it correct less than 30% over the next 48 hours. Closer to 5% due to the wall of shear ahead of it.
Member Since: Posts: Comments:
Quoting Funkadelic:
when does the next two come out? 8pm?


correct

8am, 2pm, 8pm, 2am to be exact all EDT. Although Special Advisories can be issued at any time for a developing system.
Member Since: July 7, 2005 Posts: 0 Comments: 5417
Good Afternoon Everyone, I would also like to know where the Forecast Models are. I have tried looking but can not find them. I think that a slow start to the season has given folks the false sense of it being a calm this Hurricane season.

THANKS!
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Pre-97L when it was leaving Africa. Image credit goes to Weather456 for making this loop.



Wow nice
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Funkadelic:
when does the next two come out? 8pm?


Yes. 8pm EDT
Member Since: Posts: Comments:
Here is an item for all to think about. We have had a stationary front over Northern Florida for the past month or so. If it were to get into the Gulf, what role would this front have in steering the system?
Member Since: Posts: Comments:
Huge burst of SAL off the coast of Africa. Dont look for anything develop there for quite a while.

Member Since: Posts: Comments:
Quoting Funkadelic:
when does the next two come out? 8pm?

yeah
Member Since: May 16, 2009 Posts: 1 Comments: 1231
If there was a buoy at 11.5N 52.5W I have a feeling it would be reporting light westerly winds.
Member Since: Posts: Comments:
574. bwi
First post of the season. I lurked in last night and saw Drak's post about possible favorable conditions in the Southern Caribbean, and it made me think maybe this little fellow could on-and-off develop over the next several days if it stayed south of 14 or 15n, despite marginal conditions. Sort of like Dolly last season.
Member Since: Posts: Comments:
edd, go to chat
Member Since: Posts: Comments:
562. StormW 2:47 PM AST on July 19, 2009

Thanks
Member Since: Posts: Comments:
Storm, do you remember the track that was posted by 456 about Friday or so? The one that had a storm perched in the Bahamas on Friday? Is that now reality given what you are saying?
Member Since: Posts: Comments:
569. eddye
weatherwatcher is it coming to fl
Member Since: Posts: Comments:
Quoting Grothar:
TO: nrtwlnvragn
Could you please tell me how to get the link to the models which you posted. It appears interesting. By the way, thank you for your comment on my initial picture I posted on my blog.
Question: are these dynamic models or extrapolated information for possible projections. Again, thank you all for the information you have all provided. Quite educating.


That plot is from the South Florida Water Management District website. It is a mixture of dynamic and extrapolated information. You can select More Information on that website for additional detail.
Member Since: Posts: Comments:
Pre-97L when it was leaving Africa. Image credit goes to Weather456 for making this loop.

Member Since: Posts: Comments:
Drak, no clue who the other piece of driftwood is in here.

My concern is the winds and shear values in the Caribbean. So far this system has beaten everything that has been posted about it, high shear, dry air and the such. I am concerned that in the end, it won't be us eating the crow but instead it would be the NHC.
Member Since: Posts: Comments:

Viewing: 615 - 565

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

Partly Cloudy
34 °F
Partly Cloudy

JeffMasters's Recent Photos

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