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 1182. SFLWeatherman:
WOW look at the HWRF!
Not good at all. That would be a hurricane passing through the peninsula of Haiti.
Member Since: June 30, 2013 Posts: 12 Comments: 8323
Quoting 1198. VAbeachhurricanes:
You guys are in dreamland, this thing still has another 72 hours at least to become anything. The vorticity way too weak and stretched still. As well as it will be fighting dry air.
Dry air isn't an issue, although I do agree that the circulation is broad.
Member Since: Posts: Comments:
TAZ, this summer feels like its lasting forever, no real tropical cyclone to track this summer is really taking its toll, but I love the winter and the snow we get up here in Massachusetts. Anyways let the haters hate, thats all their good for anyways, just keep on trucking forward, I know 97L is going to do the same, she has that look to her that look that it will develop at some point.
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1202. FOREX
Quoting 1189. wunderkidcayman:

Is that B B



yes
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As a certain blogger would say..
I don't poll on Sundays.
Member Since: July 8, 2005 Posts: 259 Comments: 24033
Quoting 1183. hurricaneben:


C.

Is that C C

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Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%

A. 40% / 50%
NHC is too conservative to pull out another color crayon right now. You can't blame them. They'll want better presentation. If it does well during DMIN they might move the #'s up tomorrow. This might also give them more reasons to fly a plane into it unless they're taking Labor day off as well.
Member Since: September 30, 2008 Posts: 0 Comments: 108
You guys are in dreamland, this thing still has another 72 hours at least to become anything. The vorticity way too weak and stretched still. As well as it will be fighting dry air.
Member Since: September 6, 2007 Posts: 0 Comments: 6505
1197. Kyon5

Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%
CC.
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Member Since: Posts: Comments:
I think at 8pm the NHC will bump up the percentage to 70% within 48 hours and 90% within 5 days.
Member Since: April 29, 2007 Posts: 0 Comments: 7862
Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%

BB
Member Since: Posts: Comments:
Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%



D,D for me plzs
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Quoting 1167. ncstorm:
18z SREF ensembles
I really like how this is laid out and it also shows the NAM tracks. Goes out to 4 days, so it has a higher rate of accuracy, at least we can conclude it is Caribbean bound and should make it to the Central Caribbean, after that is where the medium to long range models diverge.
Member Since: June 30, 2013 Posts: 12 Comments: 8323
as some on here have stated I now see two LLC one near 15N and 62W as one stated and the other one around 15N and 60w. IMO looks to me a repeat of dorian with competing centers
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Quoting HurricaneAndre:
F,F.
C,C.
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Quoting 1177. FOREX:


B

Is that B B

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1188. ncstorm
18z NAM shows two TC..with one moving North of the islands and 97L

Member Since: August 19, 2006 Posts: 13 Comments: 15300
Quoting 1169. beell:
As a group, over the last 2-3 hrs, I would rate the blog's ability to find a center for 97L as a fail. Someone unfamiliar with this site and its regulars would most definitely be confused.
;-)


Is it a fail if there is no center yet? ;)
Member Since: June 29, 2013 Posts: 29 Comments: 2084
1186. Gearsts
Dmin
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Anything higher than 50% over the next 48 hours is generous imo.
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Quoting 1173. Grothar:
Just when I thought I was out; they pull me back in. I just received a request from a blogger to make an announcement.

Significant blob imminent. (You happy now?)










i saw it 1st
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Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%


C.
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WOW look at the HWRF!
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Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%

BB.
Member Since: July 6, 2010 Posts: 113 Comments: 32072
Quoting 1111. kmanislander:
The center is the "eye like" feature in this image immediately to the East of Martinique which now has NW winds.



Winds at Dominica from the SSE.
Member Since: June 29, 2013 Posts: 29 Comments: 2084
Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%
F,F.
Member Since: June 11, 2013 Posts: 20 Comments: 2960
Quoting 1174. weatherlover94:



could go to 90 % 48 hours 100% in 5 days



yep with a upgrade some time late late tonight or Monday AM
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1177. FOREX
Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%


B
Member Since: Posts: Comments:
Quoting 1172. wunderkidcayman:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%
F,F.
Member Since: June 11, 2013 Posts: 20 Comments: 2960
I find it odd that 96L have not been DEACTIVATE yet
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Quoting 1162. Tazmanian:
97L is likey going too go 70% for the next 48hrs 100% the next five days



could go to 90 % 48 hours 100% in 5 days
Member Since: September 8, 2010 Posts: 0 Comments: 2209
1173. Grothar
Just when I thought I was out; they pull me back in. I just received a request from a blogger to make an announcement.

Significant blob imminent. (You happy now?)







Member Since: Posts: Comments:
Poll time
What will 97L be at the 8pm TWO?
48hs. 5 days
A 40%. A 50%
B 50%. B 60%
C 60%. C 70%
D 70%. D 80%
E 80%. E 90%
F 90%. F near 100%
Member Since: Posts: Comments:
Quoting 1162. Tazmanian:
97L is likey going too go 70% for the next 48hrs 100% the next five days

I don't see 100% over the next 5 days, not right now or tonight. I can see it tomorrow if it has a "good" night but just not right now or tonight.
Member Since: September 30, 2008 Posts: 0 Comments: 108
1170. tkdaime
will all the thunderstorms to the se of 97L strengthen it if they catch up to it
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1169. beell
As a group, over the last 2-3 hrs, I would rate the blog's ability to find a center for 97L as a fail. Someone unfamiliar with this site and its regulars would most definitely be confused.
;-)
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To my knowledge 97Ls vorticity is stretched out to the WSW, in which I think it will redevelop a surface circulation within its vorticity within the next 12 hours and once that happens then we will see development. Latest 2100utc shear and vorticity maps indicate that 500mb vorticity is increasing a sign of a mid level circulation finally developing within the large convective mass east of the surface low. If shear allows the centers to align then we can see development happen quickly as the upper level low to the northwest provides ventilation. Right now I would go with 60%/70%.
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1167. ncstorm
18z SREF ensembles
Member Since: August 19, 2006 Posts: 13 Comments: 15300
FOREX this thing is moving east,south,north,zig-zag,anywhere you like it
Member Since: June 23, 2011 Posts: 0 Comments: 1152
Quoting 1162. Tazmanian:
97L is likey going too go 70% for the next 48hrs 100% the next five days
yep,if Stewart does it.
Member Since: June 11, 2013 Posts: 20 Comments: 2960
Quoting 1162. Tazmanian:
97L is likey going too go 70% for the next 48hrs 100% the next five days
I agree.
Member Since: June 11, 2013 Posts: 20 Comments: 2960
Member Since: June 11, 2013 Posts: 20 Comments: 2960
97L is likey going too go 70% for the next 48hrs 100% the next five days
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Quoting 1153. Civicane49:


97L Looks like it's running from Pac-Man........
Member Since: September 30, 2008 Posts: 0 Comments: 108
1160. KEEPEROFTHEGATE (Mod)
T.C.F.A.
97L/INV/XX/XX
MARK
15.85N/60.71W
Member Since: July 15, 2006 Posts: 171 Comments: 53841
Once recon gets out there we will be able to get some nice solid data inputted into these models. For now we will rely on land based radar and observations from the islands and nearby ships and buoys which will work and indicate to us what is really going on at the surface.
Member Since: June 30, 2013 Posts: 12 Comments: 8323
Quoting 1151. prcane4you:
South?


no, no! its up, up, down, left, right, a, b ,up, up :)
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1157. Gearsts
Quoting 1156. CybrTeddy:
Did someone just seriously say "haters will hate" on here?
I'm not sure what to think anymore.
Is that time of the day i guess
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Did someone just seriously say "haters will hate" on here?
I'm not sure what to think anymore.
Member Since: July 8, 2005 Posts: 259 Comments: 24033
1155. WoodyFL
Quoting 1127. stormhank:
what possible track will 97l take? could it pose any affects on florida down the road??


im no expert but the new models look like it going more into the Bahamas. they were all west before. its all days away so hard to tell


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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.