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 998. belizeit:
That Oscat pass that was shown is clearly showing the system is elongated and opened to the W just as NHC mentioned in there TWO

May I remind you that the OSCAT pass was quite a few hours ago
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Quoting 999. 954FtLCane:
Hey y'all, why are we relocating a mythical COC? I'm confused. This is still an invest, a slow moving one to boot. It has an Orange colored crayon going for it. As of right now no flights are scheduled for 2 days. We've yet to see the first night of DMIN..... and some on here are calling for a COC already. I understand the OSCAT view does show some sort of center but it is elongated at best.
Guys I know everyone is desperate for a storm but really?....really?...lol.
I may not be the brightest weather geek on here but lets wait and see what happens tonight and what is left tomorrow.
It doesn't take more than 10 seconds of looking at a satellite loop to realize that 97L has a surface circulation.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
97l now at 50% chance per TWC
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1002. GatorWX
I see 97 is holding its own from my phone, trying to get stacked, waiting for dMAX.



No time to check the stats.

See ya when I get back.
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1001. ncstorm
12z HWRF


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Quoting 988. hydrus:
Are you serious.? The islands are acting like a barrier.?..So 97 has run aground.?


Would be crazy for sure... but not impossible. Let's wait to see what happens with the next 12 hrs
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Hey y'all, why are we relocating a mythical COC? I'm confused. This is still an invest, a slow moving one to boot. It has an Orange colored crayon going for it. As of right now no flights are scheduled for 2 days. We've yet to see the first night of DMIN..... and some on here are calling for a COC already. I understand the OSCAT view does show some sort of center but it is elongated at best.
Guys I know everyone is desperate for a storm but really?....really?...lol.
I may not be the brightest weather geek on here but lets wait and see what happens tonight and what is left tomorrow.
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That Oscat pass that was shown is clearly showing the system is elongated and opened to the W just as NHC mentioned in there TWO
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Quoting 985. MiamiHurricanes09:
I will say this though, if 97L manages to get into the northwestern Caribbean as an established tropical cyclone, the outcome could be catastrophic.

Ya think
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2013 Storms




All

Active

Year




Atlantic


green ball97L.INVEST


green ball96L.INVEST
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Quoting 759. opal92nwf:
Probably back in July, I had posted this picture I had made on paint saying that if my area was going to get hit with a severe hurricane, then this is what I would expect. (track more important than the fictional dates and name I put) Kind of eerie, let's see how 97L pans out.

You foresaw a hurricane ?
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Quoting 982. RascalNag:
DMIN should come by in a little over an hour. 97L is still trying to hold on to its deepest convection and refuses to collapse. It's also really determined - been huffing and puffing for hours now with smaller bursts, but it doesn't look like it'll blow the house down until the diurnal cycle is on its side. If it sustains most of its current convection through DMIN, I think it'll be well on its way to a TD or TS designation.


so the question is

is it a poofer or a puffer
stay tune we shall see

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Looks like they dropped 97L off the navy's NRL TC page
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Quoting 979. KEEPEROFTHEGATE:
I was surprised by that I figured they would of had one for just after noon tomorrow at least


Think organization suprised NHC. As late as 06Z TWO they were at 10% / 20%


Link
Member Since: September 23, 2005 Posts: 14 Comments: 11215
It is safe to say that we can expect then next TWO to be red and 70-80 Percent
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Quoting 926. ncstorm:


As someone who is in and out of jail on here..let it go, dont do it on the main..take it to sensitivethug..you wont get banned there and can say what you really want..:)

admin will address you there..I know..
Me?............ LOL... I'm totally a little pussy cat.
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Quoting 987. DonnieBwkGA:
Waiting for the GEM to run. It seems stuck.
Its been doing that..Dont know why.
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Quoting 983. CaribBoy:
The lesser Antilles are acting like a barrier (been seen several times in the past.... IRIS, MARILYN, JOSE...)
Are you serious.? The islands are acting like a barrier.?..So 97 has run aground.?
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Waiting for the GEM to run. It seems stuck.
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Member Since: May 17, 2009 Posts: 2 Comments: 904
I will say this though, if 97L manages to get into the northwestern Caribbean as an established tropical cyclone, the outcome could be catastrophic.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
As long as its closed the NHC can still classify it as a tropical cyclone, the question right now is organization of convection, if it's a broad circulation they still can classify it.
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The lesser Antilles are acting like a barrier (been seen several times in the past.... IRIS, MARILYN, JOSE...)
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DMIN should come by in a little over an hour. 97L is still trying to hold on to its deepest convection and refuses to collapse. It's also really determined - been huffing and puffing for hours now with smaller bursts, but it doesn't look like it'll blow the house down until the diurnal cycle is on its side. If it sustains most of its current convection through DMIN, I think it'll be well on its way to a TD or TS designation.
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Quoting 974. CaribBoy:


Means COC relocation further EAST


Hence comment on multiple centers.....
Member Since: September 23, 2005 Posts: 14 Comments: 11215
Quoting 974. CaribBoy:


Mean COC relocation further EAST
Yep possible
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Quoting 962. TropicalAnalystwx13:

Recon isn't investigating tonight nor tomorrow. The first flight is scheduled for Tuesday afternoon.
I was surprised by that I figured they would of had one for just after noon tomorrow at least
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Quoting 959. wunderweatherman123:
shocked nhc doesnt have it as red. needs a slightly tighter circulation. has plenty of convection. woudnt be shocked if recon found a TS by tomorrow


I'll bet the wording on the next TWO will be something along the lines of (used this before)

ANY SLIGHT INCREASE IN CONVECTION WOULD LEAD TO DEVELOPMENT OF A TROPICAL DEPRESSION
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18z NAM at 81 hours - interacting with Haiti/D.R.
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Quoting 970. nrtiwlnvragn:
Still seems to be multiple low level centers, no well defined one. Barbados is back to North winds.


Link
I wonder if the Atlantic will ever have a single vort system again...dang Y2K bug....
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I honestly see a chance we could have a TD by 5:00 am...or TS
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Quoting 970. nrtiwlnvragn:
Still seems to be multiple low level centers, no well defined one. Barbados is back to North winds.


Link


Means COC relocation further EAST
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973. ackee
since Issac 2010 I have notice quite a few storm have not move through the entire Caribbean most seem to take a turn south of Haiti chantal did the same thing this year lets see if that trend will continue with 97L if it reach TS strength
Member Since: July 15, 2008 Posts: 0 Comments: 1373
Baha said ditto...i remember those..flat,...smelly,..ditto,s.
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It's got a decent chance to be classified before recon. But don't expect rapid intensification.
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Still seems to be multiple low level centers, no well defined one. Barbados is back to North winds.


Link
Member Since: September 23, 2005 Posts: 14 Comments: 11215
Quoting 951. TropicalAnalystwx13:

There's already more than solid evidence of a closed surface circulation, as shown by surface observations and an OSCAT pass from 1536z. The circulation is too broad to classified in my opinion. Convection needs some work as well.

I'll pass on giving OSCAT the credibility of being enough evidence to support a closed surface circulation. Surface observations do support the presence of a surface circulation, that may be closed, albeit broad, hence why waiting for a good ASCAT pass is logical.

As for the convection, it's actually fairing better than I anticipated considering the lack of surface convergence now that we're in the diurnal minimum. Obviously a weak system like this is bound to fair poorly at this time. The convection will flourish perfectly fine once a consolidated closed surface circulation establishes itself. The favorable environment supports it.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 962. TropicalAnalystwx13:

Recon isn't investigating tonight nor tomorrow. The first flight is scheduled for Tuesday afternoon.
they should tomorrow if it looks even better.
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Quoting 917. CosmicEvents:
I have a Davis VantagePro2 as well.
In any price range though, I'd check with Rainmanweather.com
Not an endorsment but the owners are long-time members here and they take care of all concerns for other members.
Ditto that. I haven't been able to set anything up yet, but when I do [hopefully before next season] I'll be going w/ Rainmanwx...

Quoting 920. cchsweatherman:
I find it interesting, given the gradual development from Invest 97L, that the National Hurricane Center continues to maintain no flights scheduled until possibly Tuesday afternoon. Color me surprised on no changes to the flight plan as of yet.
Sequester.
AKA you don't get what you don't pay for. [I stand to be corrected on this.]

Quoting 928. Civicane49:
BULLETIN
TROPICAL STORM KIKO ADVISORY NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112013
200 PM PDT SUN SEP 01 2013

...KIKO WEAKENS AS IT MOVES SLOWLY NORTHWARD...


SUMMARY OF 200 PM PDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...21.8N 115.7W
ABOUT 380 MI...610 KM W OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...N OR 350 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...996 MB...29.41 INCHES
Hmmm... another sign that 97L may actually get going?

Member Since: October 25, 2005 Posts: 19 Comments: 22322
Looks interesting. The pressure pattern indicates that this would stay off the east coast in this run.

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Quoting 955. BahaHurican:
Now when u hear NCSTORM calling for Bobby McFerrin, u know it's bad...


he is the ultimate peacemaker..LOL..
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Quoting 959. wunderweatherman123:
shocked nhc doesnt have it as red. needs a slightly tighter circulation. has plenty of convection. woudnt be shocked if recon found a TS by tomorrow

Recon isn't investigating tonight nor tomorrow. The first flight is scheduled for Tuesday afternoon.
Member Since: July 6, 2010 Posts: 113 Comments: 32286
Ex-Dorian Part ii??
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Current Conditions for Dominica
Updated: Sunday, September 1, 2013
Canefield Airport

Overcast with light showers
25oC (77oF)

Overcast with light showers

Winds: West south westerly @ 03kts / 06km/h

Humidity: 86%

Barometric Pressure:
1009 mb

Accumulated Rainfall for September: 1.5 mm

Updated: 16:00 local time
(20:00 UTC)
Melville Hall Airport

Overcast and breezy with light showers
27oC (81oF)

Overcast and breezy with light showers

Winds: Easterly @ 17kts / 31km/h

Humidity: 92%

Barometric Pressure:
1011 mb

Accumulated Rainfall for September: 7.4 mm

Updated: 16:00 local time
(20:00 UTC)
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Quoting 951. TropicalAnalystwx13:

There's already more than solid evidence of a closed surface circulation, as shown by surface observations and an OSCAT pass from 1536z. The circulation is too broad to classified in my opinion. Convection needs some work as well.

shocked nhc doesnt have it as red. needs a slightly tighter circulation. has plenty of convection. woudnt be shocked if recon found a TS by tomorrow
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Based upon surface observations and the OSCAT that TropicalAnalystwx13 just posted, I do agree with some here who say that this may be at tropical depression level right now. I see enough observations and data to suggest that this may indeed be a tropical depression currently; may come down to convective organization which appears to be gradually improving. At the very least, would expect the NHC to significantly boost the outlook for Invest 97L at 8PM.
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Quoting 910. KEEPEROFTHEGATE:
I know just do me a favor keep it out of the main don't attack wab you have concearns address them too sens or her blog
You get,em Keep..it aint wab season.

GOES Imager Spectral Difference
Sep. 01, 2013 - 19:45 UTC
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Quoting 916. ncstorm:
Good Lord..where is Bobby McFerrin when you need him..
Now when u hear NCSTORM calling for Bobby McFerrin, u know it's bad...
Member Since: October 25, 2005 Posts: 19 Comments: 22322

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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.