Lesser Antilles Disturbance 97L a Threat to Develop

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

Share this Blog
70
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 155 - 105

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Quoting 145. Tazmanian:
97L could be are 1st CAT 3 hurricane of the season may be even cat 5 if wind shear is right

Horrid.thought
Member Since: Posts: Comments:
Even though model support is rather thin, sans the CMC, it would be about time we got a major hurricane. You just can't go this long without a hurricane in the Atlantic basin.
Member Since: Posts: Comments:
once pass the island we go to T.C.F.A. 18 to 24 hrs from now
Member Since: Posts: Comments:
this blog is about ready too go in two RI mode if 97L takes off
Member Since: Posts: Comments:
Quoting 149. GTstormChaserCaleb:
Convective Diagnostic Satellite Imagery over 97L showing lots of reds:


What're the reds?
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Convective Diagnostic Satellite Imagery over 97L showing lots of reds:

Member Since: Posts: Comments:
Quoting 113. GatorWX:
I just want to say, knowing what we believe steering will do and what the NHC feels (and they probably have a much better handle on this), they only gave it a 20% chance for now. Just throwing that out there so we may want to take that into consideration regarding what we're witnessing. I'm not trying to throw a brick into anyone's party.
Agree, however that was 4 hours ago and it's presentation on several aspects has improved dramatically.
Member Since: Posts: Comments:
Quoting 73. Tropicsweatherpr:
Tracks of past systems where 97L 12z position was.

Could go almost anywhere.
Member Since: Posts: Comments:
Quoting 127. TropicalAnalystwx13:
Until we get an actual developed system...if we ever do (chances look decent to me)...there's potential for some nasty stuff to go on in the western Caribbean. The LGEM now brings Invest 97L up to 103 kt, 119 mph in 120 hours.

V (KT) LGE mod 30 32 35 37 39 45 53 63 75 87 96 102 103


we just got to watch it see how it moves along once we get close to 69w then we will all know

low end cat 3 or higher is possible if it takes off
Member Since: Posts: Comments:
97L could be are 1st CAT 3 hurricane of the season may be even cat 5 if wind shear is right
Member Since: Posts: Comments:
Quoting 127. TropicalAnalystwx13:
Until we get an actual developed system...if we ever do (chances look decent to me)...there's potential for some nasty stuff to go on in the western Caribbean. The LGEM now brings Invest 97L up to 103 kt, 119 mph in 120 hours.

V (KT) LGE mod 30 32 35 37 39 45 53 63 75 87 96 102 103
LOL, I just posted the exact same thing because I didn't see your post.
Member Since: Posts: Comments:
Quoting Tropicsweatherpr:


Where are those obs from?



Grantley Adams airport
Member Since: Posts: Comments:
Quoting 133. Stormchaser2007:
From Mike Ventrice:

11 AM (15) Sep 01 84 (29) 78 (26) 29.85 (1011) W 18 10 AM (14) Sep 01 86 (30) 78 (26) 29.85 (1011) W 18 light rain showers 9 AM (13) Sep 01 84 (29) 80 (27) 29.85 (1011) W 13 8 AM (12) Sep 01 82 (28) 77 (25) 29.85 (1011)
W 16


Where are those obs from?
Member Since: April 29, 2009 Posts: 75 Comments: 14014
The NHC doesn't seem to be too excited about 97L. Even thought the models are...

This could be interesting to watch. Although I don't like WHERE it is headed.
Member Since: Posts: Comments:
Quoting 126. Seflhurricane:
97L is very close to TD status all that is missing is a well defined llc , i expect the nhc to bump development chances to 60% at 2pm


I think its getting there but the NHC is very conservative they will likely go medium chance 30-50%. LLC is becoming more define as it closes on the islands.
Member Since: Posts: Comments:
LGEM takes 97L over 100kts.
Member Since: Posts: Comments:
Quoting 135. Tazmanian:




I saw it 1st

Right you are, Taz!
Member Since: Posts: Comments:
137. SLU
Finally the season is getting out of neutral gear.

Member Since: Posts: Comments:
Quoting 121. redwagon:


Kenedy county would be nice.. King Ranch, just mostly cows.....


Somewhere around Matagorda Bay looks like a decent place for a landfall. Relatively sparse population. As long as the strongest winds can stay out of the large metropolitan areas.
Member Since: Posts: Comments:
Quoting 132. GeoffreyWPB:
1100 AM EDT SUN 01 SEPTEMBER 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 02/1100Z TO 03/1100Z SEPTEMBER 2013
TCPOD NUMBER.....13-092

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE LOW-LEVEL INVEST OF
CENTRAL CARIBBEAN SYSTEM NEAR 15.0N 72.0W FOR 03/1800Z.
3. REMARK: THE NASA 871 GLOBAL HAWK MAY FLY A 24-HOUR RESEARCH
MISSION OVER THE CARIBBEAN SYSTEM...TAKING OFF AT
03/1100Z.




I saw it 1st
Member Since: Posts: Comments:
Quoting 130. watchingnva:

Uploaded with ImageShack.us

Maybe a depression already?
Member Since: Posts: Comments:
From Mike Ventrice

Grantley Adams airport:

11 AM (15) Sep 01 84 (29) 78 (26) 29.85 (1011) W 18 10 AM (14) Sep 01 86 (30) 78 (26) 29.85 (1011) W 18 light rain showers 9 AM (13) Sep 01 84 (29) 80 (27) 29.85 (1011) W 13 8 AM (12) Sep 01 82 (28) 77 (25) 29.85 (1011)
W 16
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Member Since: Posts: Comments:

Uploaded with ImageShack.us
Member Since: September 7, 2005 Posts: 7 Comments: 1494
Member Since: Posts: Comments:
000
NOUS42 KNHC 011535
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1100 AM EDT SUN 01 SEPTEMBER 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 02/1100Z TO 03/1100Z SEPTEMBER 2013
TCPOD NUMBER.....13-092

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE LOW-LEVEL INVEST OF
CENTRAL CARIBBEAN SYSTEM NEAR 15.0N 72.0W FOR 03/1800Z.
3. REMARK: THE NASA 871 GLOBAL HAWK MAY FLY A 24-HOUR RESEARCH
MISSION OVER THE CARIBBEAN SYSTEM...TAKING OFF AT
03/1100Z.
Member Since: Posts: Comments:
Until we get an actual developed system...if we ever do (chances look decent to me)...the statistical intensity model forecasts are likely too high. However, there's potential for some nasty stuff to go on in the western Caribbean if we get a named system. The LGEM now brings Invest 97L up to 103 kt, 119 mph in 120 hours.

V (KT) LGE mod 30 32 35 37 39 45 53 63 75 87 96 102 103

(Edited to actually make sense)
Member Since: Posts: Comments:
97L is very close to TD status all that is missing is a well defined llc , i expect the nhc to bump development chances to 60% at 2pm
Member Since: Posts: Comments:
Member Since: Posts: Comments:
124. SLU
Quoting 99. watchingnva:
GO TO A ZOOMED IN RGB OR VIS LOOP AND WATCH THE LOW LEVEL CLOUD DIRECTION AROUND BARBADOS....GOES FROM MOVING ALMOST DUE NORTH TO ALMOST DUE WESTERLY IN A MATTER OF FRAMES....COC IS DEFINITELY CONSOLIDATING TO THE EAST AROUND 15N,59W...


You are right. The air is rushing into the large blob east of Martinique indicating that the pressures are lowering rather quickly there as a dominant low starts to consolidate there. Would love to have a recon investigate this today but .. oh well...

Member Since: Posts: Comments:
watch out for invest 97L MAYBE A CAT TWO HURRICANE DOWN THE ROAD.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting 87. slavicthunder:
C'mon, Gabrielle. Pull it together, hun. You're being counted on to bust a drought in the NW Gulf. Just try and avoid a Galveston landfall. Stay out of Trinity Bay, too. Avoid the refineries altogether, Gabs.


Kenedy county would be nice.. King Ranch, just mostly cows.....
Member Since: Posts: Comments:
Out for now, ya'll.. but I will check in later..
Member Since: Posts: Comments:
I think chances of 97 not developing are a lot likelier than it being a fish storm. It's running out of time for it to be a fish storm whereas there is plenty of time for it to encounter land and not strengthen at all and just be a happy ole jolly wave like some of us would rather see.
Member Since: Posts: Comments:
-12 hours



0 hours

Member Since: January 1, 2008 Posts: 0 Comments: 2684
Quoting 107. redwagon:


97L has been presenting Annular characteristics, amazing wind field symmetry! Annulars don't just die out unless they run into South America.


Yep its got a very Very strong Midlevel spin.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Looks like some outflow is beginning to form around the huge and still growing ball of deep convection.
Member Since: Posts: Comments:
Quoting 111. HurricaneHunterJoe:


My dog Josie.........Daddy, are you on that dadgum blog still? We have more important things to do!


haha, mines pretty much blind, but I'm sure he has similar reservations.
Member Since: January 1, 2008 Posts: 0 Comments: 2684
I just want to say, knowing what we believe steering will do and what the NHC feels (and they probably have a much better handle on this), they only gave it a 20% chance for now. Just throwing that out there so we may want to take that into consideration regarding what we're witnessing. I'm not trying to throw a brick into anyone's party.
Member Since: January 1, 2008 Posts: 0 Comments: 2684
.
Member Since: Posts: Comments:


My dog Josie.........Daddy, are you on that dadgum blog still? We have more important things to do!
Member Since: Posts: Comments:
Sunday morning (re)reading:

I’ve often said that the evidence for actual periodic (or even pseudoperiodic) behavior in ocean cycles is sketchy at best. What are usually quoted as periods are better referred to as characteristic time scales. Furthermore, it’s all too easy to misinterpret period analysis (usually in the form of spectral analysis) even when estimating the values of, or assessing the existence of, characteristic time scales.

I don’t deny the existence of fluctuations (which I regard as a better description). Nor do I claim that they don’t show characteristic time scales — just that the evidence is often sketchy at best. As far as being actually periodic (in the sense that knowledge of the last few “cycles” enables us to make some useful prediction of the next, or the next few, “cycles”, I believe that they’re not. ...)
in "8,000 years of AMO?"
Member Since: September 16, 2005 Posts: 0 Comments: 3141
this is going up to 30% at 2pm
Member Since: Posts: Comments:
Quoting 106. Walshy:
97L probably has better odds of not developing altogether rather than being a fish storm.




97L is not a fish storm
Member Since: Posts: Comments:
Quoting 92. TampaSpin:
Any system that stays in the Caribbean for 7 days is a scary thing. I know most models don't forecast development and i'm not sure Shear will relax enough either....but its never good to see a system in the Caribbean that long as most will develop when moving that slow. This could very well be a GOM storm eventually.


97L has been presenting Annular characteristics, amazing wind field symmetry! Annulars don't just die out unless they run into South America.
Member Since: Posts: Comments:
97L probably has better odds of not developing altogether rather than being a fish storm.

Member Since: Posts: Comments:
1500 UTC maps are in. Low level vorticity has strengthened and remained almost stationary over the last 3 hours, allowing the main convection to get closer to being stacked on top of it. Upper divergence is extremely high, but lower convergence is only okay. An anticyclone is beginning to develop over the deepest convection, and shear is in the 10-20kt range over most of the invest. Lower level winds still support a closed but elongated circulation.
Member Since: Posts: Comments:

Viewing: 155 - 105

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
71 °F
Overcast