Lesser Antilles Disturbance 97L a Threat to Develop

By: Dr. Jeff Masters , 2:46 PM GMT on September 01, 2013

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A tropical wave over the Lesser Antilles Islands (Invest 97L) is moving westward at 15 mph, and is bringing heavy rains and gusty winds to the islands. Top sustained winds in the islands as of 10 am AST Sunday were 26 mph at Monserrat. Heavy thunderstorm activity has sharply increased since Saturday, as seen on satellite loops. A large circulation is evident, with some westerly winds blowing to the south of the disturbance. However, the thunderstorms are poorly organized, and there is no sign of a well-organized surface circulation. Martinique radar shows some rotation to the echoes, though well-organized spiral bands are not evident, and do not appear to be forming. Wind shear has dropped to a moderate 10 - 20 knots over the system. An area of dry air from the Saharan Air Layer (SAL) surrounds 97L and is interfering with development.


Figure 1. Latest satellite image of Invest 97L.

Forecast for 97L
Wind shear is expected to be in the low to moderate range for the next five days, and ocean temperatures will be warm, 28 - 29°C. The disturbance is steadily moistening the atmosphere and is moving into a moister environment, so dry air will be less of an impediment to development as the week progresses. The main factor keeping the disturbance from developing over the next two days would appear to be the fact that 97L is quite large, and is stretched out from east to west over a wide expanse. Large, elongated systems like 97L usually take several days to consolidate and spin up. Another factor that will likely retard development is the presence of strong surface trade winds over the Eastern Caribbean ahead of 97L, south of the Dominican Republic. These strong trade winds are a common feature of the Eastern Caribbean, and make the region something of a hurricane graveyard. As the surface wind flow to the west of 97L accelerates into this wind max, air will be sucked from aloft downward towards the surface, creating sinking air, interfering with the formation of thunderstorm updrafts. The best chance for development of 97L would appear to be on Wednesday or Thursday, when the disturbance reaches the Central Caribbean. The wave will likely spread heavy rains to Puerto Rico, the Virgin Islands, and the Dominican Republic by Tuesday, and to Haiti by Wednesday. These rains will be capable of causing life-threatening flash flooding and mudslides in mountainous regions in Puerto Rico and Hispaniola. Of our three reliable models for predicting genesis, the UKMET, GFS, and European models, only the UKMET model develops the disturbance, predicting it will become a tropical depression south of Haiti on Wednesday, and near Jamaica on Thursday. In their 8 am EDT Sunday Tropical Weather Outlook, NHC boosted the 5-day odds of formation of 97L to 30%, and the 2-day odds to 20%.


Video 1. You can see why landslides triggered by heavy rains from a tropical cyclone are among the most dangerous hazards of these storms, thanks to a dashboard cam that caught this extraordinary rock slide in Northeast Taiwan on August 31, 2013, after heavy rains from a cold front drenched the island with up to 200 mm (7.87") of rain in 24 hours. The rains fell upon soils already saturated by Thursday's torrential rains from Tropical Storm Kong-Rey, which dumped up to 482 mm (19") of rain on Taiwan, killing three people. The driver of the car caught in the rock slide survived with minor injuries. Thanks go to wunderground member Robert Speta for bringing this video to my attention. A separate video showing the damage to the car and the course of the rock slide is here.

Jeff Masters

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Quoting 1947. scott39:
97L will have to do some amazing development in the next 24 to 36 hours to go N of the Islands. Its going to be a Caribbean cruiser and a possible GOM Beast!

Yes I agree

Member Since: June 13, 2009 Posts: 2 Comments: 12157
ASCAT caught a big ol' mess on the eastern flank.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 1940. Bluestorm5:
It wasn't really a good blog anyway, haha. Beside, I was still holding onto what Levi and Weather Channel met said on Twitter that wind shear isn't major problem anymore.
No don't say that it was a good blog, you're in University dude, so you have other assignments that is more important than this blog to complete. Right now I'm procrastinating and have a paper that is due on Wed. not really hard just 1 page, but I also would like to get started on Calculus, so I get ahead in that class, cause my fear is to fall behind and dig myself into a hole which I cannot afford.
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Quoting 1912. beell:

GOES IR (0345Z at time of post)


Going towards dmax sure doesn't seem to be helping it any. Looking fairly puny.
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Quoting 1947. scott39:
97L will have to do some amazing developement in the next 24 to 36 hours to go N of the Islands. Its going to be a Caribbean cruiser and a possible GOM Beast!


I respectfully disagree ... but that's only my opinion.
Member Since: October 6, 2007 Posts: 0 Comments: 6230
Quoting 1923. GTstormChaserCaleb:
There have been so many ULL's this year, what is the cause for so many of these ULL's?



Can you fortify a ULL with microwave?
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I'm seeing maybe like a new COC relocated near 15n and 58.5w and is pretty much stationary. What do you think ?
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Quoting 1946. Stormchaser121:

Just not gonna do it. Too early to say.


Your choice.
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1947. scott39
97L will have to do some amazing development in the next 24 to 36 hours to go N of the Islands. Its going to be a Caribbean cruiser and a possible GOM Beast!
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Quoting 1630. CaribBoy:


lol why??

Just not gonna do it. Too early to say.
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Quoting 1934. GTstormChaserCaleb:
I read it and you gave a great analysis of 97L, the one thing I disagree with you on 97L is the Upper Level environment. Wind shear to the north and in the Eastern Caribbean.


Upper-level lows are going to create wind shear. What matters is the placement. Right now, both lows are providing a favorable upper-air setup, with anticyclonic flow aloft. This favorable environment is forecast to move in tandem with the system as it tracks west. The SHIPS generally keeps shear below 10 knots, which is very conducive.

Anyways, night guys.
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Is it just me or does this thing look nearly stationary?



('sup Kori!)
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at 2am down to 30% at 48 hors
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Quoting 1939. GTstormChaserCaleb:
Goes over PR on this run.



The wave to the east of 97L must be responsible of the right shift
Member Since: October 6, 2007 Posts: 0 Comments: 6230
Looks now like ULL is taking convection NE and decoupling it from the low...


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Quoting 1934. GTstormChaserCaleb:
I read it and you gave a great analysis of 97L, the one thing I disagree with you on 97L is the Upper Level environment. Wind shear to the north and in the Eastern Caribbean.

It wasn't really a good blog anyway, haha. Beside, I was still holding onto what Levi and Weather Channel met said on Twitter that wind shear isn't major problem anymore.
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Quoting 1933. CaribBoy:
EXTREMELY INTERESTING 00Z GFS and CMC
Goes over PR on this run.

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97L and 50W wave will merge and could go more N
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1937. JLPR2


OSCAT caught part of the broad spin of the TW behind 97L, pretty far south.
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GEM wants to make one system out of 97L and the system behind it.
Member Since: August 2, 2011 Posts: 0 Comments: 2044
Quoting 1926. TampaSpin:
time to pop some popcorn....grab a coke....put my pjs on and I am going to stick around for the 2am update......what will the percent % be...guesses?


20% IN 48 hrs. 30% in 5 days.
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Quoting 1929. Bluestorm5:
Kind of disappointing I didn't get blog out while this main blog is still active. Not many views or comments.
I read it and you gave a great analysis of 97L, the one thing I disagree with you on 97L is the Upper Level environment. Wind shear to the north and in the Eastern Caribbean.

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EXTREMELY INTERESTING 00Z GFS and CMC
Member Since: October 6, 2007 Posts: 0 Comments: 6230


Fl has the early lead, but we've heard that before.
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AOI approaching 97L.....
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Quoting wxgeek723:
Since the brink of satellite technology, no. Every season has them, and I believe almost, if not all, Septembers in the reliable record have produced at least one. 

hmm-do you think there will be a hurricaneless season in the future?
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Kind of disappointing I didn't get blog out while this main blog is still active. Not many views or comments.
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1928. Thrawst
Quoting 1926. TampaSpin:
time to pop some popcorn....grab a coke....put my pjs on and I am going to stick around for the 2am update......what will the precent % be...guesses?


Still 40% for 48 hrs out and 50% 5 days out.
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Quoting 1925. GTstormChaserCaleb:
GEM out to 54 hrs.



mmm
Member Since: October 6, 2007 Posts: 0 Comments: 6230
time to pop some popcorn....grab a coke....put my pjs on and I am going to stick around for the 2am update......what will the percent % be...guesses?
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GEM out to 54 hrs.

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nice tropical wave with t.storm on land here looking better then invest 97L WITH no rain with it!
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There have been so many ULL's this year, what is the cause for so many of these ULL's?

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This is far out in time.

Member Since: August 2, 2011 Posts: 0 Comments: 2044
Quoting 1896. KoritheMan:


Yes. We had one at 3:00 this afternoon.


Tell me what happened please Sir. I have to work early after closing and can't keep up. tia
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Quoting 1915. redwagon:


Oh, I'm very calm. I just want you to answer all those questions, the wx ones anyway. Haven't been able to watch 97L since 11a, I need someone - you - to fill me in.


I too have been away since Church this morning...I just logged on this evening about 10pm....so I really don't know what it looked like today....I can only say what it looks like now....ITS POORLY ORGANIZED and waiting to see if DMAX has any influence. One thing is certain it appears, a weak system will travel further West, while a stronger system not as far west before turning.
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the rules of the road are simple be polite and to the weather at hand this thing has started to reform similar to marlin the water temps and high pressure ridge with the moister flow all point to be alert.....by 4 am ast we should have a better idea.....this is a sleeper and one i won't ignore for one reason i'm in the firing range. thanks
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Quoting 1907. GTstormChaserCaleb:
I raised this question earlier on the chances that TW approaching 97L gives life to it and actually causes a shift in track like what the GFS is showing now which takes it north of the islands?

It still loks like the wave behind 97l develops and takes a track north of 97L while 97l tangles with hispanola or continues south of it on a westerly track.
Member Since: August 2, 2011 Posts: 0 Comments: 2044
Took lot of energy from this busy college student to get this decent blog post out. Enjoy!!!

Bluestorm5's Blog on 97L
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Quoting 1899. TampaSpin:


calm down....I did not say it was going to develop....I just pointed out the next 24 maybe even 36 hours will be important for a more northerly pull if development was to occur. If no development then further west it goes!


Oh, I'm very calm. I just want you to answer all those questions, the wx ones anyway. Haven't been able to watch 97L since 11a, I need someone - you - to fill me in.
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So.................... what did I say earlier regarding 97L and the W CARIB.......

Member Since: October 6, 2007 Posts: 0 Comments: 6230
Quoting 1908. Maineweatherguy20023:

Has there ever been a season w/out a hurricane. 1917 doesnt count. that wasnt a season.
Since the brink of satellite technology, no. Every season has them, and I believe almost, if not all, Septembers in the reliable record have produced at least one. 
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1912. beell

GOES IR (0345Z at time of post)
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1911. GatorWX
Quoting 1904. MelbourneTom:
One more try to post the image.



tis the season
Member Since: January 1, 2008 Posts: 0 Comments: 3424
the rules of the road are simple be polite and to the weather at hand this thing has started to reform similar to marlin the water temps and high pressure ridge with the moister flow all point to be alert.....by 4 am ast we should have a better idea.....this is a sleeper and one i won't ignore for one reason i'm in the firing range. thanks
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Quoting 1906. JLPR2:


I'm not interested in it developing or at least in it reaching hurricane strength, I want 2013 to break 2002's latest hurricane record.

XD
Yeah... hate me blog. LOL!
And we're sooo close too. The GFS is a believer. Don't think we're gonna make it though. 
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Quoting JLPR2:


I'm not interested in it developing or at least in it reaching hurricane strength, I want 2013 to break 2002's latest hurricane record.

XD
Yeah... hate me blog. LOL!

Has there ever been a season w/out a hurricane? 1917 doesnt count. that wasnt a season.
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I raised this question earlier on the chances that TW approaching 97L gives life to it and actually causes a shift in track like what the GFS is showing now which takes it north of the islands?

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1906. JLPR2
Quoting 1891. KoritheMan:


This is one instance where I'm hoping dmax doesn't help its chances of cyclogenesis tomorrow.

My storm is coming! :P


I'm not interested in it developing or at least in it reaching hurricane strength, I want 2013 to break 2002's latest hurricane record.

XD
Yeah... hate me blog. LOL!
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1905. GatorWX
Quoting 1887. KoritheMan:


He's highly ignorant. Ignore him.


Perhaps he is young and was unaware.
Member Since: January 1, 2008 Posts: 0 Comments: 3424

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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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