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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5 to 15kt shear forcast i forcasted not seeing anything to be higher over coc.I think the shear weakens or stays same before getting stronger.Morning will tell what i am saying and that the wrf will most likely be right.Otherwise gota go,laterz alls.
It's not moving southwest, shear from the northern half of the invest is making look like it's moving that direction when it is clearly moving WNW. 20 knot shear will hit the COC in a few hours.
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1863. amd
Quoting HurricaneKing:
Link

You can see the band of high clouds heading toward the coc. And the convection near the coc beginning to shear out.


that last floater image shows the reason why 97L will be RIP shortly. Convection is trying to blow up around the supposed center of 97L and being sheared heavily from west to east.

The fate of 97L was sealed when the upper level high trying to build into the caribbean didn't break the TUTT, but instead deformed the TUTT so that it would send stronger shear east of the islands, especially south of 15 north.
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Quoting btwntx08:
no one riping the storm remember it tricked us in coming back this morning so don't let your guard down again i bet you'll be suprised tomorrow morning imo

I'm going to stay up late tonight so I don't get surprised in the morning.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting FloridaTigers:
Watch. 97L during Dmax will explode and tighten, and the blog will make a 180.

"I knew it'd rebound!"


When conditions change from day to day and hour to hour, the most sensible people change their opinions with the way things go, things happen and are fluid
Quoting BurnedAfterPosting:


I dont think its dead either, too many times many call off systems even if it didnt look good and yet they find a way to form

I think shear is about to hit it, but I have a feeling it will find someway to survive the shear
I was under the impression you were also calling it a goner. I guess not?
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Quoting wunderkidcayman:

what can you show me the light that is in the darkness for 97l(please show me where you got that from)

According to the XTRP it is going slightly north of west
Member Since: May 16, 2009 Posts: 1 Comments: 1231
1856. Patrap
Earlier..



Latest..

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Watch. 97L during Dmax will explode and tighten, and the blog will make a 180.

"I knew it'd rebound!"
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Quoting stoormfury:
97L is now moving southwest and trying to refire

what can you show me the light that is in the darkness for 97l(please show me where you got that from)
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Quoting Acemmett90:
I usesally a wish caster but this is one dead storm


I dont think its dead either, too many times many call off systems even if it didnt look good and yet they find a way to form

I think shear is about to hit it, but I have a feeling it will find someway to survive the shear
Quoting BurnedAfterPosting:


agreed, it is clear we have some in denial this evening lol


I'm not in denial, I'm now thinking this is not going to blow up due to shear. I'm just saying the actual COC is not in the 20 knot range yet, very close though and should be in there within the next few hours. I'm in the same boat as you this time, this is not going to do anything but get shredded over the next few days. Watch the Anticyclone in the WC.. That might be a player in a few days. I called out 97L last night, I'm calling ti to gradually weaken tonight now that the shear is worse then I expected. Not RIPing it yet though.
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1850. 0741
Quoting canesrule1:
I'm looking at the cimss website and I'm definitely noticing that the shear is lifting north to around the Bahamas, thoughts?
shear is not moving out it kill 97l on monday
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1849. KEEPEROFTHEGATE (Mod)
hey ace you may be replace with empty space
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Well, there's no naked swirls and seems to broadening the coc with each turn and with cooler tops. Steering still suggests a westerly, possibly swesterly movement - which would help it tremendously until it can get under the shear. I'm not sure shear is as much the problem with 97L as the missing lower level convergence - maybe because it's such a small system, maybe because it it can't get a bonified llc going near the surface.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
the coc is still under tstms not effected by any shear.Even if 15kt that really doesn't effect systems a lot.Dmax still to come.
Seen a lot better here.
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Quoting stoormfury:
97L is now moving southwest and trying to refire


its not moving SW, its moving just north of due west, shear is making it look like its moving SW
Quoting HurricaneKing:
Link

You can see the band of high clouds heading toward the coc. And the convection near the coc beginning to shear out.


yup it is pretty clear on the loops
97L is now moving southwest and trying to refire
Member Since: August 22, 2006 Posts: 0 Comments: 2711
I am denial,the truth is the coc is in 10kt.I said earlier 5 to 15kt all night.Max 3 to 4 day shea ris 5 to 15kt or below.
Link

You can see the band of high clouds heading toward the coc. And the convection near the coc beginning to shear out.
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Quoting HurricaneKing:


I would say looking at the floater the stronger shear is just starting to hit the coc.


agreed, it is clear we have some in denial this evening lol
northern part def in shear/20 to 25kt.Coc not effected only 10kt.
Quoting reedzone:
Actually north of the COC is 20 knots, on the north side. The center is still under 10 knots of wind shear. If you don't believe me, check the coordinates and look at the current shear.


I would say looking at the floater the stronger shear is just starting to hit the coc.
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1834. KEEPEROFTHEGATE (Mod)


INV/97L/XX
MARK
13.2N/53.6W
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Actually north of the COC is 20 knots, on the north side. The center is still under 10 knots of wind shear. If you don't believe me, check the coordinates and look at the current shear.
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Working now.. sorry
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Quoting StormJunkie:
Looks like shear is already 20knts over the system.


Look closely, it's still at 10 knots, but I agree, shear will increase by the morning.
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Ah thank you both.
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1827. ssmate
Well, I hate to disappoint everyone, but I'm heading off to bed. You can catch my lurks tomorrow at 11:00 AM and 5:00 P.M.
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Quoting BurnedAfterPosting:


no SJ is right 20 knots going right over the system as we speak


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Quoting TampaMishy:
I can't remember do they put out a new update at 11?

Only if there is a tropical entity
Member Since: May 16, 2009 Posts: 1 Comments: 1231
I can't remember do they put out a new update at 11?
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Very likely what will happen BAP...But we watch for those outside chances...Think you mentioned the same thing last night in relation to 97 fighting off the dry air and very weak circulation.
Member Since: August 17, 2005 Posts: 26 Comments: 16828
I'm looking at the cimss website and I'm definitely noticing that the shear is lifting north to around the Bahamas, thoughts?
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Its 10 to 15kt currently.The south part in 10kt.center in 15kt.This may persist overnight but might even weaken a little as some models show.I am not using neighter the ships or gfs for my shear forcast.
Run this water vapor loop and you can see the shear impacting it...
Member Since: August 17, 2005 Posts: 26 Comments: 16828
I compare what might be about to happen to 97L to a fly being squished by a fly swatter lol

not pretty lol
1815. Vero1
MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE MIAMI FL
226 PM EDT SUN JUL 19 2009

... GLOBAL MODELS CONTINUE TO INDICATE THAT THE
NORTHERN EXTENT OF A TROPICAL WAVE NEAR 70W MOVING WEST TOWARD
THE TURKS AND CAICOS ISLANDS WILL SPLIT OFF AND MOVE NW THROUGH
THE LENGTH OF THE BAHAMAS...DELIVERING INCREASED SHOWERS AND
TSTMS. A PAIR OF TROPICAL WAVES BEHIND THIS WILL MIGRATE ACROSS
THE CARIBBEAN THROUGH MIDWEEK..MAINTAINING 20 TO 25 KT EASTERLY
WINDS MAINLY S OF 23N TO INCLUDE THE SOUTHERN BAHAMAS AND TURKS
AND CAICOS. THE PERSISTENT STRONG EAST FLOW WILL ALLOW SEAS TO
BUILD TO 10 FT IN E SWELL OVER MUCH OF THE AREA BETWEEN THE
LEEWARDS AND THE SOUTHERN BAHAMAS THROUGH MIDWEEK. DECAYING SE
SWELL MIGRATES NW TO THE EAST OF THE BAHAMAS THU AND FRI.
THE RIDGE AXIS SHIFTS SOUTHWARD THU AND FRI...WITH WINDS AND SEAS
DIMINISHING.
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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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