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 BurnedAfterPosting:
new shear map out, shear increasing right by the system

I have to say the NHC is right with this system, dont expect that yellow circle to change at 8pm

Sorry to kill everyone's spirits lol


Rofl...starting to sound like me. Welcome to the dark side. (puts cool sunglasses on)
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I also did a TCFC:

Total Points of Invest 97L - 34
Total Need for Issuance of a TCFA - 35-38

Highlights:

A circulation is evident on visible, shortwave infrared, microwave imagery or QuikSCAT [check]

Winds associated with system are at least 25 knots [check]

A weather station reported a pressure drop of 2 mb [check]

The estimated MSLp is less than 1008 mb [uncheck]

Westerly flow above disturbance less than 15 knots [check]

SSTs are above 26C [check]

System has persisted for 24 hrs [uncheck]

Dvorak Classification of 1.5 or greater [check]

NWP genesis considerations (NOGAPS, GFS, UKMET, ECMWF) [uncheck]

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This blog is so bipolar...
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It actually looks somewhat similar to Felix. Right now its a wait and see, although it would be interesting to see if 97L can form an Anti-cyclone
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Quoting WaterWitch11:


what is the problem with caps? do think you think i'm yelling? i'm not just trying to type fast. i'll use lower case

To be honest with you I dont know haha. it is harder to read and takes up more space haha. i just hate reading caps but in the end it doesnt bother me as much as it bothers others.
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Increased shear east of the Islands and digging southward
Afternoon Chief,..looks like a lil sumthing to track.

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Has improved it's poleward outflow channel:
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Quoting HaboobsRsweet:

I think anyone on here is willing to help you learn and us learn from you. I just think they are asking a simple request not to use caps because it is a pain in the neck. If you are respectful to others then I am sure they will return the favor. That is at least what I have noticed.


what is the problem with caps? do think you think i'm yelling? i'm not just trying to type fast. i'll use lower case
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I want to take it home with me and pet it lol!
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Enhanced Infrared (IR) Imagery (4 km Mercator)

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Your welcome.
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Quoting WaterWitch11:


YOUR RIGHT AND I DIDN'T LAST THE PREVIOUS YEAR! BECAUSE THE WAY YOU GUYS TREAT PEOPLE WHEN THEY ARE JUST TRYING TO LEARN.

I think anyone on here is willing to help you learn and us learn from you. I just think they are asking a simple request not to use caps because it is a pain in the neck. If you are respectful to others then I am sure they will return the favor. That is at least what I have noticed.
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THANKS FOR THE LINK PATRAP
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Quoting BurnedAfterPosting:
20 knots of shear on its northern side as well

I see no indication that TUTT is lifting north

Go here. Shear Loop
Member Since: May 16, 2009 Posts: 1 Comments: 1231
2km Storm Relative IR Imagery with BD Enhancement Curve



Storm Relative 16km Geostationary Water Vapor Imagery


AMSU Intensity Time Series
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Quoting WeatherStudent:


May I copy and paste your post to remind you of it tomorrow night?

Absolutely...if I am wrong I can admit it. Just my opinion of the situation. I have learned a lot just from this one wave hanging on and the mechanics of it have been every interseting.
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745. IKE
Quoting FloridaTigers:
So what exactly is missing for TD classification then? Defined LLC?


Red circle j/k:)
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting WxLogic:


If it slows down too...


Yes slowing down would definitely help. Give more time to the trough to lift out.
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WaterWitch11 you are ignored and reported
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741. IKE
Quoting WxLogic:


lol... 1 MB.


Hey...we've got folks giving half-hour updates on waning and waxing.

Might as well update the mb's and winds.

Member Since: June 9, 2005 Posts: 23 Comments: 37860
The TUTT is moving north. In previous updates it was closer to Jamaica.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
NOAA RAMMB imagery for AL97 (great new site in 2007!)

Currently Active Tropical Cyclones

Last Updated 14 Minutes Ago.




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97L is acting like a snow plow. It is going through and opening up all kinds of space and clearing the way for the next wave to push through. I really think early August is going to be very interesting. I am looking forward to see what comes about the first and second week.
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So what exactly is missing for TD classification then? Defined LLC?
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Quoting IKE:
It's moved south of north...

BREAKING NEWS(sorry for caps)....pressure dropped one mb.

MORE BREAKING NEWS(sorry for caps)...winds up to 30 mph.


lol... 1 MB.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
Slowly strengthening...
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evrything good,hoping that shear will killed the wave before reaching any land mass
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Quoting Drakoen:


Look at the shear in front of it. As long as it stays it it's current latitude it will be fine. 5-10 knots of shear ahead.


If it slows down too...
Member Since: August 14, 2008 Posts: 4 Comments: 5038
20 knots of shear on its northern side as well

I see no indication that TUTT is lifting north
729. IKE
It's moved south of north...

BREAKING NEWS(sorry for caps)....pressure dropped one mb.

MORE BREAKING NEWS(sorry for caps)...winds up to 30 mph.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting WaterWitch11:


I CAN DO WHATEVER I WISH


That's true, but you probably won't last long here.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting Drakoen:


Look at the shear in front of it. As long as it stays it it's current latitude it will be fine. 5-10 knots of shear ahead.


yea but the shear has increased and moved further south

Again it will be close, you are right though, right in front of it shear is still favorable

I will say this, could it possibly create a small anticyclone itself to protect from the higher shear?


looking at visible, definitely starting to organize well.
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Quoting BurnedAfterPosting:
new shear map out, shear increasing right by the system

I have to say the NHC is right with this system, dont expect that yellow circle to change at 8pm

Sorry to kill everyone's spirits lol

Makes sense, like a few of us have been saying for the last two days, once it gets closer to the windward island shear levels will be too much. The ridge building in that most said was going to happen never did. There were little signs over the last two days that it would. I do not expect it to survive tonight and if it does it wont make it through Monday night.
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the winds have increased to 30mph
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WHXX01 KWBC 191813

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

1813 UTC SUN JUL 19 2009



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



ATLANTIC OBJECTIVE AIDS FOR



DISTURBANCE INVEST (AL972009) 20090719 1800 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

090719 1800 090720 0600 090720 1800 090721 0600



LAT LON LAT LON LAT LON LAT LON

BAMS 12.2N 52.5W 13.0N 56.5W 14.6N 60.5W 16.0N 64.5W

BAMD 12.2N 52.5W 12.5N 54.8W 12.9N 57.2W 13.4N 59.7W

BAMM 12.2N 52.5W 12.7N 55.4W 13.5N 58.4W 14.4N 61.4W

LBAR 12.2N 52.5W 12.4N 56.0W 13.0N 59.8W 13.8N 63.7W

SHIP 25KTS 30KTS 35KTS 38KTS

DSHP 25KTS 30KTS 35KTS 38KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

090721 1800 090722 1800 090723 1800 090724 1800



LAT LON LAT LON LAT LON LAT LON

BAMS 17.8N 68.6W 21.6N 75.7W 24.9N 79.4W 27.5N 79.5W

BAMD 13.9N 62.7W 15.1N 70.0W 16.3N 77.6W 16.6N 84.7W

BAMM 15.4N 64.8W 17.9N 72.3W 20.5N 78.7W 22.1N 83.2W

LBAR 14.9N 67.6W 17.3N 74.6W .0N .0W .0N .0W

SHIP 42KTS 50KTS 56KTS 61KTS

DSHP 42KTS 50KTS 53KTS 58KTS



...INITIAL CONDITIONS...

LATCUR = 12.2N LONCUR = 52.5W DIRCUR = 270DEG SPDCUR = 21KT

LATM12 = 12.4N LONM12 = 48.2W DIRM12 = 270DEG SPDM12 = 20KT

LATM24 = 12.3N LONM24 = 44.2W

WNDCUR = 25KT RMAXWD = 40NM WNDM12 = 20KT

CENPRS = 1012MB OUTPRS = 1014MB OUTRAD = 125NM SDEPTH = M

RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM



$$

NNN
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Quoting jasoniscoolman09:
WOW THE STORM IS MOVING WEST AT 25 MPH THAT CRAZY. EVERYTIME WE GET A NEW UPDATE THE STORM IS GOING FASTER ALL THE TIME..
Why do you persist in using caps lock ? It's not necessary and very annoying so please take it off for the second time now. As for water witch if you are so tired why don't you go rest ?
Member Since: October 9, 2008 Posts: 0 Comments: 8436
Quoting BurnedAfterPosting:
new shear map out, shear increasing right by the system

I have to say the NHC is right with this system, dont expect that yellow circle to change at 8pm

Sorry to kill everyone's spirits lol


Look at the shear in front of it. As long as it stays it it's current latitude it will be fine. 5-10 knots of shear ahead.
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The TUTT continues to lift:
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Drakoen:


45


NOT QUITE SURE WHAT THIS MEANS
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good afternoon everyone, regardless of development at least we have something to talk about besides global warming LOL
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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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