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 SLU:



Hmmm ... no longer tonight but in 24 to 48hrs time. Why the sudden change of thinking.


Might have to do with the latest GFS shear model showing shear more favorable than it did in previous runs
1513. Drakoen
Pasch is on duty; I like Pasch.
Member Since: October 28, 2006 Posts: 57 Comments: 30615
18z HWRF shows nothing.
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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)
Member Since: July 8, 2005 Posts: 259 Comments: 24484
Quoting Funkadelic:
I say lets take a little break off of 97L and play name that blogger!!

You simply remember this blogs funniest things, or quotes that bloggers have written in the past.

Like does anyone rember last year when STORMW was accused of sending messages to a female blogger on here?
something about feet lol anyone remember?



Hmmm StormW I see you are avoiding the above post... as i wasn't around when that happen, wait, i probably dont wanna know lol.
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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.
that sounds good at this time :)
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1508. SLU
Quoting weatherwatcher12:
000
ABNT20 KNHC 192350
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 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 400 MILES EAST OF THE WINDWARD ISLANDS CONTINUES TO
SHOW SIGNS OF ORGANIZATION. UPPER-LEVEL WINDS ARE EXPECTED TO
BECOME LESS FAVORABLE FOR THE DEVELOPMENT OF THIS SYSTEM OVER THE
NEXT 24 TO 48 HOURS
. 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.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH




Hmmm ... no longer tonight but in 24 to 48hrs time. Why the sudden change of thinking.
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Guarantee that tomorrow morning when it goes through the DMAX most uneducated people will say it will be a TD. Then we'll go through the DMIN...and you get the idea.
Member Since: June 9, 2007 Posts: 4 Comments: 15946
Quoting hurricane23:
Maybe it will re fire up in a couple of days in the central carib...

Adrian


In the month long animations I've made in the past, you can see this happening over and over again. The head gets ripped off, but the wave persists and continues its movement...and then BAM! There ya go...cyclonic activity.
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1505. Patrap
"Yous People"..is that Like Italian or Bronx?

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Quoting CybrTeddy:
So it continuing to show signs of organization.. yet they keep it at Yellow.


due to the impending shear, still a good choice to keep it at yellow
1503. Drakoen
It really is the QuickSCAT
Member Since: October 28, 2006 Posts: 57 Comments: 30615
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.
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Quoting StormW:


Don't know...haven't looked yet...I'll take a peek.
storm are u going to post a new synopsis or update
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1499. eddye
people tonight your going to see this system really develop and in the morning we will havea td and you people wil be surprise
Member Since: August 12, 2008 Posts: 0 Comments: 1281
So it continuing to show signs of organization.. yet they keep it at Yellow.
Member Since: July 8, 2005 Posts: 259 Comments: 24484
1367. Mikla
Awesome picture - thanks for posting.
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1496. Patrap
QuikSCAT Ocean Page

This page contains the most recent wind vector images covering the Atlantic Ocean, Indian Ocean, East Pacific and West Pacific Ocean. It is updated shortly after receipt of new QuikSCAT orbit data files.

QuikSCAT is a polar orbiting satellite with an 1800 km wide measurement swath on the earth's surface. Generally, this results in twice per day coverage over a given geographic region.

Click desired image for more features.
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Quoting IKE:


Does it ever pick up systems? j/k...

Looks like the RIP-ers have backed off some since the new TWO came out. I'm sure they'll be back tomorrow fired up with 30 minute frame-by-frame updates on 97L.


RIP-ers? lmao I'm literally chuckling up a storm right now.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1494. Drakoen
Quoting Nolehead:
1474. Funkadelic 12:00 AM GMT on July 20, 2009
I say lets take a little break off of 97L and play name that blogger!!

You simply remember this blogs funniest things, or quotes that bloggers have written in the past.

Like does anyone rember last year when STORMW was accused of sending messages to a female blogger on here?
something about feet lol anyone remember?


no contest...JFV would win every catagory...



LOL!
Member Since: October 28, 2006 Posts: 57 Comments: 30615
Quoting Nolehead:
1474. Funkadelic 12:00 AM GMT on July 20, 2009
I say lets take a little break off of 97L and play name that blogger!!

You simply remember this blogs funniest things, or quotes that bloggers have written in the past.

Like does anyone rember last year when STORMW was accused of sending messages to a female blogger on here?
something about feet lol anyone remember?


no contest...JFV would win every catagory...



LMAO!!!!!!!!!!!
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Quoting Drakoen:


I haven't changed from this morning lol.


i put you in the wrong category didnt i :P

edit: well actually you've been slowly lowering your expectations of the system as the system got closer to the shear/TUTT/trough, and the trough just sitting there not moving.
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1490. Patrap
A better Orbit?

No better Orbit for a Twice a day pass than a Polar Orbit.
Or am I missing something?
Ouikscats passes are determined by orbital Mechanics,..a known path is published every day on what will be collected on each ascending and descending node of the Polar Orbit.
A better way of saying it missed,is that the Storm missed the Quikscat pass..

to be er,..retentive.
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Quoting StormW:


Doing good...you?


Im great, thanks. A bit tired from the day but im relaxing now so its all good.
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1474. Funkadelic 12:00 AM GMT on July 20, 2009
I say lets take a little break off of 97L and play name that blogger!!

You simply remember this blogs funniest things, or quotes that bloggers have written in the past.

Like does anyone rember last year when STORMW was accused of sending messages to a female blogger on here?
something about feet lol anyone remember?


no contest...JFV would win every catagory...

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1482. Patrap
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Quoting Drakoen:
Quicksat missed 97L What A Surprise.

I wish it was in a better orbit
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Don't know about you all, but considering how this disturbance has continued to prove us wrong and the changes its gone through, I'm not going to make a conclusion either way. I'm just going to let Mother Nature do its thing while I sit back and enjoy the show.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
1479. Drakoen
Quoting HurricaneSwirl:
everyone who is saying poof right now was probably saying it should become ts ana when it was flaring up this morning. MOST people that do that change their opinions every single diurnal phase. at DMAX apparently a hurricane is forming. at DMIN apparently everything is dead. i admire the people on here that stick with their predictions like and acknowledge the fact that there is a DMAX after DMIN like reedzone, MLC, terranova and more. Also the people that change their predictions but based on evidence and facts such as hurricane23 and drak, etc. also deserve respect.


NOTE: I am NOT saying this for this specific moment only. im just talking about the during general diurnal phases. a lot of people have a reason to poof it right now because it might run into a block of shear and get shredded to bits, no one really knows yet, and this isn't directed at anyone specifically..


I haven't changed from this morning lol.
Member Since: October 28, 2006 Posts: 57 Comments: 30615
1478. IKE
Quoting Drakoen:
Quicksat missed 97L What A Surprise.


Does it ever pick up systems? j/k...

Looks like the RIP-ers have backed off some since the new TWO came out. I'm sure they'll be back tomorrow fired up with 30 minute frame-by-frame updates on 97L.
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StormW

what's your feel on the convection in the GOM...
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everyone who is saying poof right now was probably saying it should become ts ana when it was flaring up this morning. MOST people that do that change their opinions every single diurnal phase. at DMAX apparently a hurricane is forming. at DMIN apparently everything is dead. i admire the people on here that stick with their predictions like and acknowledge the fact that there is a DMAX after DMIN like reedzone, MLC, terranova and more. Also the people that change their predictions but based on evidence and facts such as hurricane23 and drak, etc. also deserve respect.


NOTE: I am NOT saying this for this specific moment only. im just talking about the during general diurnal phases. a lot of people have a reason to poof it right now because it might run into a block of shear and get shredded to bits, no one really knows yet, and this isn't directed at anyone specifically..
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And a good evening to you as well Sir Storm :p
How are you this fine sunday eve?
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1471. Drakoen
Quicksat missed 97L What A Surprise.
Member Since: October 28, 2006 Posts: 57 Comments: 30615
Quoting HaboobsRsweet:

As Nole said as well, the pattern down here in the Gulf States has been so weird this year. First it was over 100 for 5 days in a row which never happens until August...lack of sea breeze but maybe a handful of times this year, and now a solid front passing through and temps have been really low to the point when we had a solid land breeze a few days ago.


Very good point! I have never experienced a hotter June that I can remember. I know those gulf waters have got to be warm. And yea, then the sudden front. Strange weather is an understatment. Im waiting for snow next...lol.
Maybe its the dreaded "El Nino!!" (enter scary music)
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convection now refiring near the MLC, DMAX will be very interesting
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Quoting futuremet:
Latest frames are showing an emerging convection pulse. If this continues within the next 3hrs, watch the blog make a 180. lol

Havent change my thoughts and even if there is some convection tonight, still wont. This will never make TD status.
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1465. Drakoen
"same ol' boring bickering..."
Member Since: October 28, 2006 Posts: 57 Comments: 30615

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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.