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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Hollow.
Member Since: Posts: Comments:
I am 1 for 1 on this game and I'm going for:
Yellow @ 8PM
Member Since: January 14, 2007 Posts: 17 Comments: 4140
Quoting BaltOCane:


ok... but just a bit.


lol that a boy
Member Since: July 7, 2008 Posts: 2 Comments: 3237
962. CUBWF
Hi ws, I don't think is correct you to talk like that. Believe me, most of the cuban, don't talk like that, I don't think Yamil does.
It's not apropiate. Take it just like an advice.
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961. HadesGodWyvern (Mod)
India Meteorological Department

Tropical Cyclone Outlook (0600z 19JUL)
========================================
Convective clouds are seen over center and adjoining parts of north Bay of Bengal

Convective clouds are also seen over parts of northwest and southeast Arabian Sea

MONSOON WATCH
===============

The axis of monsoon trough at mean sea level passes through Ganganagar, Meerut, Bareilly, Gorakhpur, Bhagalpur and center of well marked low pressure area and thence southeastwards to eastcentral Bay of Bengal.

Chief Meteorological Forecast (1200z 19JUL)
===========================================
The well marked low pressure area over northwest Bay of Bengal and neighbourhood persists. It is likely to intensify into a depression during next 24 hours.
Member Since: Posts: Comments:
Quoting HurricaneSwirl:


i see ive came on at the wrong time... you need to lighten up just a bit ;)


ok... but just a bit.
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Quoting Funkadelic:
WoW forget about 97L... I got a serious storm on my way here in boca.. I was watching TWC and during that stupid ice cream and cake commercial, the red ticker on the bottom of the screen came on and says I will be seeing winds in excess of 70mph, and Deadly lightning..and possible hail.


Anyone here in westpalm beach being affected?


Yep, looks like were in for some hail.

Member Since: Posts: Comments:
LOL, all the downcasting, shear-mongering can keep right on going - LOL, this baby's rocking!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Quoting DestinJeff:
if enough bloggers here doubt the NHC forecast, then surely they will adjust accordingly ... those instruments, computers, etc you see in the background during live shots from the Center are props ... the real forecasters monitor the posts here on their laptops for relevent information, so some lag in the official forecast from NHC is to be expected.


lol- sometimes I wonder if anyone at the NHC or other well known mets read this blog.

Anyone remember last year when there was bashing of Stephanie Abrams from TWC for her "worst-case scenario" storm? (A Cat 5 that hits New Orleans then magically reappears in the Atlantic to hit NYC?!) A blogger shows up defending Abrams that I swear must have really been her...
Member Since: Posts: Comments:
Nothing surprises me with the NHC anymore
Member Since: October 28, 2006 Posts: 57 Comments: 30724
Quoting BaltOCane:


how about "no"?


i see ive came on at the wrong time... you need to lighten up just a bit ;)
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting WeatherStudent:


Back it up with facts.


Brother dont need to lol, iam entitled to my opinion correct? Just dont see to much future with this disturbance.I find it funny how some of you question the word of the NHC i get a kick out of it in all honesty.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
Quoting AllStar17:
You can clearly make out a COC on this, and you can still see the feeder band wrapping around the system. IMO, no signs of shear affecting the system yet.

Invest 97L Floater : Visible Loop


Interesting to see how thunderstorm are developing in the inflow.
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I will go with A. Doubt they drop it until it is totally gone but dont seem them increasing it either.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting HurricaneSwirl:


SHOWERS HAVE GOTTEN FURTHER ORGANIZED WITH THE SYSTEM WITH 500 MILES EAST OF THE LESSER ANTILLES. THIS EXTREMELY ORGANIZED SYSTEM IS PROJECTED TO BECOME A CATEGORY 4 IN THE NEXT 48 HOURS, BUT DUE TO THE HOSTILE ENVIRONMENT OF JEFFMASTERS BLOG ON THE WEATHERUNDERGROUND, THERE IS A LOW CHANCE...LESS THAN 30%...OF DEVELOPMENT OVER THE NEXT 48 HOURS.


how about "no"?
Member Since: Posts: Comments:
You can clearly make out a COC on this, and you can still see the feeder band wrapping around the system. IMO, no signs of shear affecting the system yet.

Invest 97L Floater : Visible Loop
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945. eye
hurricane23 speaks the truth, like i mentioned several pages ago...shear has already begun to affect the system (slowly but surely).
Member Since: August 21, 2006 Posts: 0 Comments: 147
The outer 'band' looks rather healthy on 97L. Although the central convection is rather ragged. We'll see what happens tonight. Although im still not expecting this to go over TS strength at the moment.
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Quoting beell:


But really, I gotta change that-should be the "trough tied to the ULL"

Dsylexic's UNTIE!

sorry, UNITE!


Lol. I thought you had it right the first time.

Good Afternoon Everyone.

Looks like the NWS has a sense of humor as well..


ENJOY THIS PATTERN BECAUSE IT SHOULD KEEP TEMPERATURES NEAR NORMAL WHICH WE
HAVE NOT SEEN THAT MUCH THIS SUMMER. THE DROUGHT SHOULD EASE SOME OVER THIS
PACKAGE AS WELL AS RAINS BEGIN TO ACCUMULATE ACROSS THE REGION. THE RAINS ARE
WELCOME AT THIS POINT SINCE TREE ROOTS ARE GETTING HIGH ENOUGH TO TRIP ON.

Lol. I just love a good pun. :)
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A because that is them.
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Quoting WeatherStudent:
Gang, any early stabs on what the 8pm TWO from the NHC will read? Just for jokes.


SHOWERS HAVE GOTTEN FURTHER ORGANIZED WITH THE SYSTEM WITH 500 MILES EAST OF THE LESSER ANTILLES. THIS EXTREMELY ORGANIZED SYSTEM IS PROJECTED TO BECOME A CATEGORY 4 IN THE NEXT 48 HOURS, BUT DUE TO THE HOSTILE ENVIRONMENT OF JEFFMASTERS BLOG ON THE WEATHERUNDERGROUND, THERE IS A LOW CHANCE...LESS THAN 30%...OF DEVELOPMENT OVER THE NEXT 48 HOURS.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting weatherwatcher12:

I don't think that they would do that


I am pretty sure he was being sarcastic. We need a sarcasm tag on the blog.
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Quoting DestinJeff:
if enough bloggers here doubt the NHC forecast, then surely they will adjust accordingly ... those instruments, computers, etc you see in the background during live shots from the Center are props ... the real forecasters monitor the posts here on their laptops for relevent information, so some lag in the official forecast from NHC is to be expected.



LOL
Member Since: October 28, 2006 Posts: 57 Comments: 30724
Already signs of shear pinching on the mid-level circulation.Nice overall wave
unfortunatly upper conditions in front aren't to promising.

Adrian
Member Since: May 14, 2006 Posts: 8 Comments: 13841
Quoting Stormchaser2007:


ROFL...Its an invest. Only major hurricanes can create hot towers.


nope, check my blog. Carlos was a cat 2 when NASA observed the hot towers. Hot towers are simply tall cumulonimus clouds. Anthing with deep conective clouds from TD to cat 5 can have hot towers, infact, a TS with hot towers will likely become a hurricane. However, it is unlikely than the towering nimbus on 97L rises to 15 km (hot towers)
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Quoting weatherwatcher12:

Anything has the potential :)


It is IMPOSSIBLE for invests to develop hot towers. Pat cue the hot tower video! lol
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Quoting BurnedAfterPosting:
well we could do the same poll question again

Poll closes at 7pm EDT

What will the circle look like for the 8pm TWO?

A) Yellow
B) Orange
C) Red
D) Circle will be removed

VOTE NOW!!


If its not B then Brennan and Blake need to get their eyes checked.
Member Since: October 28, 2006 Posts: 57 Comments: 30724
Quoting DestinJeff:
if enough bloggers here doubt the NHC forecast, then surely they will adjust accordingly ... those instruments, computers, etc you see in the background during live shots from the Center are props ... the real forecasters monitor the posts here on their laptops for relevent information, so some lag in the official forecast from NHC is to be expected.


finaly someone gets it...lol
Member Since: June 3, 2008 Posts: 0 Comments: 1934
Quoting BaltOCane:
how can one tell (on the radar pictures) when the convection is increasing? is it the presence of cool tops or more precip? or looking for circulation?
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929. amd
I vote A: NHC will keep 97L at a low chance for development (<30%)
Member Since: August 29, 2005 Posts: 0 Comments: 1024
928. eye
A
Member Since: August 21, 2006 Posts: 0 Comments: 147
927. CUBWF
B
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting DestinJeff:
if enough bloggers here doubt the NHC forecast, then surely they will adjust accordingly ... those instruments, computers, etc you see in the background during live shots from the Center are props ... the real forecasters monitor the posts here on their laptops for relevent information, so some lag in the official forecast from NHC is to be expected.

I don't think that they would do that
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Weather456:
97L pass just south of here



Wow, pressure dropped like a rock.
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Hopefully for the sanity of the blog...it should read like this.

SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE
LOCATED ABOUT X MILES EAST OF THE WINDWARD ISLANDS HAS BECOME
BETTER ORGANIZED OVER THE PAST SEVERAL HOURS.
CONDITIONS ARE CURRENTLY FAVORABLE FOR SOME DEVELOPMENT OF THIS
SYSTEM...ALTHOUGH UPPER-LEVEL WINDS ARE EXPECTED TO BECOME LESS FAVORABLE
TONIGHT OR TOMORROW. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL AND
GUSTY WINDS COULD AFFECT THE WINDWARD ISLANDS ON MONDAY AS THE WAVE
MOVES WESTWARD AT 15MPH. THERE IS A MEDIUM CHANCE...30-50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

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Quoting BaltOCane:


B... with cautious optimism :)


B
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Im going with A too because I feel the NHC is still considering the shear
Quoting Stormchaser2007:


ROFL...Its an invest. Only major hurricanes can create hot towers.

Anything has the potential :)
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Stormchaser2007:


B with 60% confidence.


B... with cautious optimism :)

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Quoting yamil20:
based on recent visible images, is me or the system is creating some hot towers?


I've been noticing them, too. However, the angle of the sun is getting low in the sky, so it may just be shadows cast by lower cloudtops.
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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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