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 1298. BahaHurican:
This looks REAL familiar... everybody has had these heavy rains this summer...

Good to see u , junky.


This is probably the 4th rain event like this. The past two have been 2.77" or lower but this one is a new high in such a short span. 3.74" in less than two hours makes things rather WET! Good to see you too! Hope things are going well in your neck of the woods!
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1304. LargoFl
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Quoting 1294. OracleDeAtlantis:
Someone show me the center of this thing.


I think its near 15N/62W, just my take though, within a degree either way.
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Quoting 1273. DonnieBwkGA:
954FtLCane You're right. There was also 1950's Hurricane King which Cuba didn't seem to hurt much. Hit Miami as a 955 mb Cat 3. The Cat 3 rating is from HURDAT. I don't know why wunderground has it as a Cat 2. Unusual cyclonic track.



Most of central part of Cuba is not as mountainous as the western part allowing for a storm not too weaken all that much when making the cross. There is one small area which can be viewed on the map shown below.

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Quoting 1294. OracleDeAtlantis:
Someone show me the center of this thing.
Nobody knows including Stormpetrol Maybe in the middle.
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1300. scott39
Quoting 1293. GTstormChaserCaleb:
End of the NAVGEM run:

Thats a more likely track.
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One ominous sign for 97L--most frequent bloggers are absent.
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Quoting 1282. hurricanejunky:
Rain rates up to 6.33"/hr here in North Fort Myers today. Just now letting up. This is what 3.74" in 2 hours looks like in our front yard:


I REALLY hope we don't see a tropical system, especially a slow mover. This has been a VERY wet rainy season thus far.
This looks REAL familiar... everybody has had these heavy rains this summer...

Good to see u , junky.
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Quoting 1287. hydrus:
Imprecise-caster.!


Is that new?
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Quoting 1293. GTstormChaserCaleb:
End of the NAVGEM run:


I agree completely with this. I'm a bit surprised at how well the NAVGEM has been performing as of late; it was the only model to pick up development of Fernand in the Bay of Campeche.
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Quoting 1292. stormpetrol:
97L % should be up to 70% at 7cst and 90% over a 5 day period, IMO it will probably upgraded to a TD by tomorrow morning , just my take.


Yea I agree....especially if D Max is nice to it.
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Quoting 1265. stormpetrol:


Convection starting to pop very near the center now.
Someone show me the center of this thing.
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End of the NAVGEM run:

Member Since: June 30, 2013 Posts: 12 Comments: 8428
97L % should be up to 70% at 7cst and 90% over a 5 day period, IMO it will probably upgraded to a TD by tomorrow morning , just my take.
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Invest 97L should remain on a nearly due west heading for the next 3-4 days. I'd put it west/west-northwest of Jamaica as it begins to feel the forecast weakness. The only reason a few models send it into the Greater Antilles (i.e. Hispaniola) is because they develop 97L in earnest in the eastern Caribbean. This is unlikely to occur.
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1290. LargoFl
Quoting 1285. DonnieBwkGA:
How much rain in say 48 or 72 hours would it take to get Lake Okeechobee above 18 feet?
its been raining down there almost all day long
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Quoting 1280. sporteguy03:
97L reminds me alot of Hurricane Ernesto 2006 Cyberteddy. In terms of possible track.
A fair comparison. 
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1288. LargoFl
gee the east coast is getting whacked big time, 2nd night in a row in the same area's.......
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1287. hydrus
Quoting 1242. DonnieBwkGA:


I was imprecise. I should have said development of African waves in the eastern Atlantic becomes a lot less likely after 3 weeks.
Imprecise-caster.!
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1286. KEEPEROFTHEGATE (Mod)
97 got some more travelling to do yet percents may remain the same for 48 but increase for the 5 day maybe

its up to the NHC
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How much rain in say 48 or 72 hours would it take to get Lake Okeechobee above 18 feet?
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1284. LargoFl
Quoting 1270. ncstorm:


the CMC is taking names..

will it be right, only time will tell
ive been saying that all along..the cmc was the only G model that picked up on 97..now the rest of them are following its lead..congrats cmc..you've earned your stripes.
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Quoting 1265. stormpetrol:


Convection starting to pop very near the center now.
What center?
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Rain rates up to 6.33"/hr here in North Fort Myers today. Just now letting up. This is what 3.74" in 2 hours looks like in our front yard:


I REALLY hope we don't see a tropical system, especially a slow mover. This has been a VERY wet rainy season thus far.
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I think the oven is on in the Caribbean.Get ready for a plate for possible Hurricane Gabrielle.
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97L reminds me alot of Hurricane Ernesto 2006 Cyberteddy. In terms of possible track.
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1279. scott39
I think the NHC will keep 97L at 40/50%. It is stretched out like silly putty. the 500mb vorticity is finally starting to show a tiny dot of yellow on the map. 97L is going to take time to organize. I would lean towards more organization at 70W to 75W. This would keep 97L going W longer. I could see it tracking over the W end of Cuba. The models that are showing a stronger system N of the Islands...I dont buy. An Invest has to stack itself from top to bottom and have a closed off LLC to make TD status. Im not saying 100% that 97L cant do it before the western Caribbean...but it would be a shock if it did.
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I don't get why some people post the comments they do.
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Quoting VAbeachhurricanes:
Warming cloud tops



Sure there warming theres currently very
Quoting kmanislander:
Convergence gone again, just like same time yesterday.

No upgrade unless and until this system can maintain a decent state of organization. I bet that within 2 to 3 hours the deep convection refires again around 62W. Very frustrating following these weak disorganized lows.



No cyclone developing anytime..
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Peak DMIN, I'll admit I've seen things far worse than 97L around this time.


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Quoting 1267. GTstormChaserCaleb:
18z NAM looks similar to the 12z CMC:



Seems to be the most popular path over the past few years. Everyting that forms smashes into Haiti/D.R. and gets eaten for lunch.
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Quoting 1267. GTstormChaserCaleb:
18z NAM looks similar to the 12z CMC:






Oooohh.. If it goes over Hispaniola like Chantal it will get ripped to shreds by the high terrain.
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954FtLCane You're right. There was also 1950's Hurricane King which Cuba didn't seem to hurt much. Hit Miami as a 955 mb Cat 3. The Cat 3 rating is from HURDAT. I don't know why wunderground has it as a Cat 2. Unusual cyclonic track.


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Listen to Doc. My man SAL is getting ready to deflate this room tomorrow. Doc said no chance till 9/11...and even that is a small chance. Wave train over too.
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Quoting 1265. stormpetrol:


Convection starting to pop very near the center now.



It's one of them where the Thunderstorms go away and come right back.
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1270. ncstorm
Quoting 1267. GTstormChaserCaleb:
18z NAM looks similar to the 12z CMC:



the CMC is taking names..

will it be right, only time will tell
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By 180 hours and beyond the GFS is out to lunch and puts rain everywhere (GOM, Cuba, Islands, etc).
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Quoting 1253. Newswatcher:



Okay. So if it stays as a weak TS and goes under Cuba and then becomes a hurricane would it still turn North or would it continue west?



If it becomes a hurricane it's more likely to be pulled north. If it waits until near Cuba or Jamaica it would be pulled north into the GOM. If it gets real strong real fast it would be pulled North near Hispaniola or Cuba
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18z NAM looks similar to the 12z CMC:

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Quoting 1251. VAbeachhurricanes:
Warming cloud tops



Maybe if it can shed that convection to the East and rebuild a proper CDO it will finally get its act together. Start with a clean slate.
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Convection starting to pop very near the center now.
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1264. LargoFl



The Local Weather Forecast for St Kitts and Nevis



Valid up to 8 pm tomorrow Monday 2nd September 2013.
Today's Temps
High 32°C
90°F
Low 26°C
79°F

Cloudy

Synopsis: A vigorous tropical wave is approaching the Eastern Caribbean. It will increase the chances for cloudiness, showers, and thunderstorms over the next twenty four hours.

Wx: Skies tonight will be partly cloudy to cloudy with brief passing showers. Tomorrow, skies will be partly sunny at first but becoming increasingly cloudy with moderate to heavy showers and thunderstorms.

Winds: ENE at 14-20 kts gusting higher in showers.

Seas: Moderate to locally rough, waves 1.8m/6ft. Small craft operators should exercise caution.

Barometric Pressure: Below normal

Sunrise tomorrow: 6:41 am.

Sunset tomorrow: 5:49 pm.





Antigua and Barbuda Meteorological Services
Orvin Paige-Forecaster

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That track reminds me of hurricane david, born and raised here in east central florida, i remember that storm for sure, along with rest of them that have came through here or close to the coast.
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Some models are picking up something starting from the vorticity at 50w 12n.

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Quoting 1241. BahaHurican:
That's Only because u don't live in The Bahamas or S FL....



True. It's also true that I don't wish these things on anybody, not even the dingbats that want 'em.
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GFS at 177 hours - 97L finally breaks free of land, but not a lot left of it.
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Convergence gone again, just like same time yesterday.

No upgrade unless and until this system can maintain a decent state of organization. I bet that within 2 to 3 hours the deep convection refires again around 62W. Very frustrating following these weak disorganized lows.

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Quoting 1248. jascott1967:
95 degrees here in beautiful "downtown" Kem

Hurrican Zeta formed on December 29,2005a Cape Verde storm. Never know.
Prometheus was in that year too.
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One can make out the coc right here on the Day/Night Visible which looks like it just passed the 60 west longitude line and around 12-13 north latitude.

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Look! It's the El Reno tornado!

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1255. SLU
Quoting 1234. stormpetrol:


I looked carefully at the loop again, simple as that :)



That's the old MLC from this morning. The LLC is NE of Barbados and drifting westwards.
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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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