97L growing more organized, will bring heavy rain to the Lesser Antilles

By: Dr. Jeff Masters , 15:55 GMT le 19 juillet 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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It would obviously have to expand it's moisture field as much as possible before getting slammed by the shear.
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good night yall hope you all rest well tonight. RIP 97L just kidding i hope i am kidding
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Link

Swirl looks to be about 13lat/54long give or take a few degrees
ShearMap
Shear is 20-30 in that area (on this map).

Swirl meets Shear.
Does this help you to understand what is probably going to happen?



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Hey everyone..sorry I have not been on pretty much all season..I have been very busy with work and trying to get my life back...I will try to be in more often now that the season should start to ramp up.

also my website will be one of my to do's this week..I need to get it back up and running again.

Anywho, My opinion on 97L is it has had it's ups and downs for the past 24 hours and I believe there will be enough of it left after enduring the shear to start to develop into possible a depression or TS. However I could be wrong as I have before...I just don't see such a vigorious system falling apart so quick.
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As you can see the appearance of the blob is clearly one that is being sheared.

1910. Patrap
Anytime Mishy..
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TY Patrap!
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Would somebody please explain to me how 97L can survive what it is up against? please give me an example!!!
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the small area of convection is clearly being sheared

Easily seen on WV loop...
Member Since: 17 août 2005 Posts: 26 Comments: 16874
1906. Patrap
Drew Brees and Bobby Hebert about to get Boxed..

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1905. amd
Quoting btwntx08:

read my post careful what u say?


i saw your no RIP post, but as of right now, I can't logically see a scenario where this storm survives.

Shear is already 20 knots over a very small cored system, will increase in the next 24 hours, and worse, it is oriented directly west to east because of the locations of the upper level highs in the eastern atlantic, and the coast of south america respectively.

There will be other blobs to study, and once the wave near the african coast clears 40 West, it should be west of the SAL and gain latitude. Then, maybe this season will finally begin.

Member Since: 29 août 2005 Posts: 0 Comments: 1024
1904. pottery
post 1895.
OK
Member Since: 24 octobre 2005 Posts: 0 Comments: 24884
Quoting Patrap:
Bobby "Hebert" ..




And he is in the box.
Member Since: 15 août 2008 Posts: 0 Comments: 2515
Quoting STORMMASTERG:
The coc is in that small tstm cluster to the northwest is the arm thats being sheared.


no the small area of convection is clearly being sheared
...but instead deformed the TUTT...

Any chance that the deformation of the tutt is part of it breaking as well?

I was looking at imagery and the CIMMS maps and it seems there is a small area on the tendency map that is decreasing just to the E of the northern islands...So could it be breaking?

I am way out of my league with this question, but noticed I at least managed not to use The Word....lol
Member Since: 17 août 2005 Posts: 26 Comments: 16874
Quoting Patrap:
XTRAP is the acronym for "Extrapolated",which is the Invests current heading ,"extrapolated thru the Forecast Period",..peroid.

Its not a Model at tall.

I know. I was just using it to show the current direction it was moving.
Member Since: 16 mai 2009 Posts: 1 Comments: 1231
The coc is in that small tstm cluster to the northwest is the arm thats being sheared.
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1898. Patrap
Bobby "Hebert" ..Boxed.




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Quoting cchsweatherman:
Photobucket

Been doing some in-depth analysis tonight in regards to Invest 97L and decided to share my findings and try to establish the current situation through graphic display.

Throughout the day, Invest 97L has been getting better organized with an increasingly better defined low-level structure noted with some banding becoming established. During the afternoon and evening, it seemed that the system mixed out some mid-to-upper level dry air that remained and in combination with diurnal minimum, caused the convection to significantly wane. In the past couple hours, it seems that the system is trying to build some convection over the assumed center which would give it more promise.

In the meantime, a rather strong upper level low over the open Atlantic south of Bermuda induced a TUTT (tropical upper tropospheric trough) over the Eastern and Central Caribbean creating very hostile wind shear over the region. This can clearly be seen with the streaming pattern in the thunderstorm clouds over the region. Throughout the day, this hostile wind shear has continued and really hasn't eased much at all. In fact, it almost seems as the TUTT had expanded further south deeper into the Eastern Caribbean.

Based upon the latest computer models, the TUTT should gradually lift out of the region and into the SW Atlantic in the coming days. At the same time, an upper level anticyclone (or upper level high) should become established over the Western and Central Caribbean creating a more favorable upper level environment. This should happen in about two to three days as this will be rather slow to occur.

Continuing with the computer models, Invest 97L (should it survive the rather unfavorable wind shear that it will encounter starting sometime tomorrow afternoon) should begin to take on a more WNW to NW heading in about 24 hours as it rides the southeastern periphery of a deep layered ridge in the open Atlantic. If this does indeed verify and if the system survives to this point, it would then become under the influence of the upper level anticyclone which would give it a better chance for development.

After that point, things become too cloudy for any reasonable forecast, so that will have to wait for now.

For now, I'm not going to discount Invest 97L's chances for possible further development since the current computer model trends offer it better hope than this morning, but I'm not totally sold either. Just going to have to wait and see what becomes of Invest 97L.

Here's a good view of the ULL
Member Since: 16 mai 2009 Posts: 1 Comments: 1231
1896. Patrap
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Quoting pottery:
The extrap. is not a model of anything.
It is the track that the system will take, IF IT FOLLOWS THE EXISTING TRACK.


yea and that is what watcher was doing, he was using the XTRAP to show it was moving just north of due west
Does anyone know if 97L is going to reach the Hebert box?
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Keeper is the center of circulation south of any covection that is left in 97L? Is it being ripped apart right now?
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1892. Patrap
XTRAP is the acronym for "Extrapolated",which is the Invests current heading ,"extrapolated thru the Forecast Period",..peroid.

Its not a Model at tall.
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1890. pottery
The extrap. is not a model of anything.
It is the track that the system will take, IF IT FOLLOWS THE EXISTING TRACK.
Member Since: 24 octobre 2005 Posts: 0 Comments: 24884
1889. KEEPEROFTHEGATE (Mod)
Quoting Acemmett90:
Could this be the next blog destroying blob lol
a little low needs to come up to 11 12 n then ya
Member Since: 15 juillet 2006 Posts: 178 Comments: 56089
Quoting reedzone:
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.

I don't see that way, reed. 20 kts of shear is bad, but not detrimental; plus, it is only on the northern side of the system. There's no shear at the mid-levels which is where this system's organization is. Sure, the upper level shear may be blowing the tops off as it tries to ventilate, but that's not a killer. The problem is that it's not getting lower convergence, imo, moreso than it's being effected by shear. And, I don't agree with the movement either - I think it's still heading mostly west. Every steering layer, unless they haven't been updated, still show a westerly movement.
Member Since: 9 juillet 2006 Posts: 184 Comments: 29610
Quoting JRRP:

do not look that model


huh? the XTRAP tells you how it is moving, he is right to be looking at the model
Quoting BurnedAfterPosting:
yup shear is definitely hitting that small core of convection now

shear is higher than 15 knots by the center, it is absolutely clear


Ahh, whatever.. the shear map is pretty much a few hours old now, so shear is probably a bit over 15 knots over the COC
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its clearly moving west.I can even see it with 1 eye/2 helps it.
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Been doing some in-depth analysis tonight in regards to Invest 97L and decided to share my findings and try to establish the current situation through graphic display.

Throughout the day, Invest 97L has been getting better organized with an increasingly better defined low-level structure noted with some banding becoming established. During the afternoon and evening, it seemed that the system mixed out some mid-to-upper level dry air that remained and in combination with diurnal minimum, caused the convection to significantly wane. In the past couple hours, it seems that the system is trying to build some convection over the assumed center which would give it more promise.

In the meantime, a rather strong upper level low over the open Atlantic south of Bermuda induced a TUTT (tropical upper tropospheric trough) over the Eastern and Central Caribbean creating very hostile wind shear over the region. This can clearly be seen with the streaming pattern in the thunderstorm clouds over the region. Throughout the day, this hostile wind shear has continued and really hasn't eased much at all. In fact, it almost seems as the TUTT had expanded further south deeper into the Eastern Caribbean.

Based upon the latest computer models, the TUTT should gradually lift out of the region and into the SW Atlantic in the coming days. At the same time, an upper level anticyclone (or upper level high) should become established over the Western and Central Caribbean creating a more favorable upper level environment. This should happen in about two to three days as this will be rather slow to occur.

Continuing with the computer models, Invest 97L (should it survive the rather unfavorable wind shear that it will encounter starting sometime tomorrow afternoon) should begin to take on a more WNW to NW heading in about 24 hours as it rides the southeastern periphery of a deep layered ridge in the open Atlantic. If this does indeed verify and if the system survives to this point, it would then become under the influence of the upper level anticyclone which would give it a better chance for development.

After that point, things become too cloudy for any reasonable forecast, so that will have to wait for now.

For now, I'm not going to discount Invest 97L's chances for possible further development since the current computer model trends offer it better hope than this morning, but I'm not totally sold either. Just going to have to wait and see what becomes of Invest 97L.
Member Since: 14 avril 2007 Posts: 8 Comments: 5169
1881. JRRP
Quoting weatherwatcher12:

According to the XTRP it is going slightly north of west

do not look that model
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1879. KEEPEROFTHEGATE (Mod)
Quoting Acemmett90:

keeper
do you have a problem with my opinon
it was in response to the viedo posting i know admin dont like that there to much its one reason to be put right where you just come from nothing more
Member Since: 15 juillet 2006 Posts: 178 Comments: 56089
1877. pottery
The Extrapolation Model ??
I love it!
Member Since: 24 octobre 2005 Posts: 0 Comments: 24884
Quoting DestinJeff:
Top 10 Blog Posts of the Evening:

10. Shear is 20knts
9. Shear is 10 knts
8. Shear killed 97L
7. Shear is forecast to move north
6. Shear is splitting in two
5. Shear took the "What kind of wind are you?" quiz with the result: Westerly
4. Shear is aiding 97L
3. Shear is back to 20 knts
2. Shear is increasing/decreasing
1. Shear,shear, shear, shear, shear, shear, shear, shear ...

CALGON, TAKE ME AWAY!
LOL
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1875. Patrap

AL97 Floater 1 - RGB Color Infrared Loop
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Quoting STORMMASTERG:
Its mvoing west at 15mph.

It is moving north of west acording to the extrapolation model.
Member Since: 16 mai 2009 Posts: 1 Comments: 1231
yup shear is definitely hitting that small core of convection now

shear is higher than 15 knots by the center, it is absolutely clear
Its mvoing west at 15mph.
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1871. KEEPEROFTHEGATE (Mod)
Quoting FloridaTigers:
Watch. 97L during Dmax will explode and tighten, and the blog will make a 180.

"I knew it'd rebound!"
last night it was the same way but 1 pm this afternoon it had a score of 34 one away out of a T.C.F.A. now its dead done finish lets move on its amazing how the opinion goes on the blogs

myself iam in a

watch wait see mode
Member Since: 15 juillet 2006 Posts: 178 Comments: 56089
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
na tomorrow things wud be ok 97l wud not develop soon
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1867. Patrap
..Nighty 97L...ZZZzzzzzzzzzz

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1866. Patrap
..Im getting sleeeepy..
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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.
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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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