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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2205. LargoFl
Hazardous Weather Outlook

------------------------------------------------- -------------------------------
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
530 AM EDT MON SEP 2 2013

FLZ039-042-043-048>052-055>057-060>062-065-GMZ830 -850-853-856-870-
873-876-022200-
LEVY-CITRUS-SUMTER-HERNANDO-PASCO-PINELLAS-HILLSB OROUGH-POLK-
MANATEE-HARDEE-HIGHLANDS-SARASOTA-DESOTO-CHARLOTT E-LEE-
TAMPA BAY WATERS-TARPON SPRINGS TO SUWANNEE RIVER OUT 20 NM-
ENGLEWOOD TO TARPON SPRINGS OUT 20 NM-
BONITA BEACH TO ENGLEWOOD OUT 20 NM-
TARPON SPRINGS TO SUWANNEE RIVER OUT 20 TO 60 NM-
ENGLEWOOD TO TARPON SPRINGS OUT 20 TO 60 NM-
BONITA BEACH TO ENGLEWOOD OUT 20 TO 60 NM-
530 AM EDT MON SEP 2 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WEST CENTRAL AND SOUTHWEST
FLORIDA.

.DAY ONE...TODAY AND TONIGHT.

...THUNDERSTORM IMPACT...
A MOIST AND UNSTABLE ATMOSPHERE WILL ALLOW FOR SCATTERED SHOWERS
AND THUNDERSTORMS TO DEVELOP NEAR THE COAST THIS MORNING AND MOVE
INLAND THROUGH THE DAY. SOME OF THESE STORMS COULD PRODUCE
LOCALLY HEAVY RAINFALL...GUSTY WINDS...AND FREQUENT CLOUD TO
GROUND LIGHTNING.


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2204. LargoFl
Quoting 2202. VR46L:


Exactly ! BOC this year is about the only place any thing is spining up ...Have been watching that wave a couple of days looks better today than yesterday !
..yes and hopefully some of its rain will get to texas..
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If this is the right hand side of my dream of a double landfall this year, then the right side should take a path very similar to this. This is roughly the motion I saw.

Post 2553. OracleDeAtlantis 9:33 AM GMT on July 08, 2013



If above is the correct right side in my forecast dream, then the left side of what will become a double landfall should begin to take shape also, and conditions are looking more favorable at the moment.

Post 39. OracleDeAtlantis 4:02 PM GMT on August 29, 2013


I saw the left side appear below the Yucatan, in the Eastern Caribbean, roughly here ... it then moved northwest across the Yucatan, and hooked left, making landfall close to the Texas-Mexico border.



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2202. VR46L
Quoting 2198. LargoFl:
good morning, I think that wave is supposed to go into the BOC the NHC said yesterday..


Exactly ! BOC this year is about the only place any thing is spining up ...Have been watching that wave a couple of days looks better today than yesterday !
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2201. LargoFl
cmc at 90 hours.......
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2200. VR46L
I see the GFS is more interested in the TW enroute to the Gulf Too....

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2199. LargoFl
Good Morning Folks!..Coffee is perking,looks like we're going to need it lol..
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2198. LargoFl
Quoting 2191. VR46L:
surprised there is no talk of the TW going towards the GulF ....



good morning, I think that wave is supposed to go into the BOC the NHC said yesterday..
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2197. VR46L
Quoting 2194. GatorWX:


...was just going to post that.


LOL !!

was going to post Great minds think alike but remembered the second half of the saying ...
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2196. IKE
6Z GFS @ 153 hours....


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The storms this season are annoying ><

"IMA DO DIS...naawww."
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2194. GatorWX
Quoting 2191. VR46L:
surprised there is no talk of the TW going towards the GulF ....





...was just going to post that.
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2193. GatorWX


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97 is odd one most of it just sitting east of the leewards. another wierd one in a yr of many odd invest.
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2191. VR46L
surprised there is no talk of the TW going towards the GulF ....



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2190. VR46L
Quoting 2181. OracleDeAtlantis:
It's clear that what happened yesterday was that Gabby inhaled a lot of dry air. You can clearly see the results tonight from the gigantic outflow boundaries that flew out her tail end on the east and southeast side.

I think this eastern blowout, is the largest outflow boundary I've ever seen.

The flip side of that burst of convection is the envelope of moist air has expanded just as fast, so the next burst of convection should be able to sustain itself far better.

Welcome to the Caribbean Gabby. We hope you enjoy your warm vacation.



Gabby ???? LOL



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2189. GatorWX
Did someone put TX out in the Atlantic? :)




Not so stretched looking this morning.
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Quoting 2182. hurricanes2018:
maybe a new storm to watch to


Most likely a fish but YES fun to watch...

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nice tropical wave
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we may not get another actual cv development. considering we had the indicators for an active season just got to sit back and say umm. 96 looked like a sure bet we know what happined to that one
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2185. barbamz




Coast of West Africa and SAL. Have a nice day, folks!
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2183. vis0
CREDIT: NASA (WV & EnhIR, enhanced & blended through most of the animation)
INVEST 97L 201309-01.1045_201309-02;0415U
                                                    re-sizable  800x600 HERE
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maybe a new storm to watch to
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It's clear that what happened yesterday was that Gabby inhaled a lot of dry air. You can clearly see the results tonight from the gigantic outflow boundaries that flew out her tail end on the east and southeast side.

I think this eastern blowout, is the largest outflow boundary I've ever seen.

The flip side of that burst of convection is the envelope of moist air has expanded just as fast, so the next burst of convection should be able to sustain itself far better.

Welcome to the Caribbean Gabby. We hope you enjoy your warm vacation.

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2180. barbamz
Good morning with Toraji, southwest of Japan:





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2178. VR46L
The Main models don't like you , the NHC are not enamored ....
Preforming poorly right now ..yes there is a little blow up of convection ...but looks mostly devoid of thunderstorms and convection ...


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Quoting 2174. moonlightcowboy:
COC coordinates: 14.8n,58.5/59w? What does everyone else see?


And, there looks now to be convection firing south of there, directly over Barbados.



the plot thickens.......

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TROPICAL DEPRESSION KIKO DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112013
200 AM PDT MON SEP 02 2013

THE REMAINING DEEP CONVECTION ASSOCIATED WITH KIKO DISSIPATED
OVERNIGHT...AND THE CYCLONE HAS BECOME A SWIRL OF LOW- TO MID-LEVEL
CLOUDS. DVORAK INTENSITY ESTIMATES CONTINUE TO QUICKLY FALL...AND
A BLEND OF THE LATEST T- AND CI-NUMBERS SUGGEST AN INITIAL INTENSITY
OF 30 KT. THE CYCLONE IS EXPECTED TO CONTINUE TO SPIN DOWN AND
BECOME A REMNANT LOW AS IT MOVES OVER COOL WATERS AND IN A STABLE
ENVIRONMENT. DISSIPATION OF THE REMNANT LOW IS FORECAST IN A DAY
OR TWO...WHICH IS SUPPORTED BY THE DYNAMICAL MODEL GUIDANCE.

NIGHTIME VISIBLE SATELLITE IMAGES SHOW THAT KIKO HAS SLOWED
DOWN WITH AN INITIAL MOTION ESTIMATE OF 335/4 KT. THE CYCLONE
IS PREDICTED TO CONTINUE SLOWING DOWN TODAY AS IT BECOMES
SITUATED IN AN AREA OF WEAK LOW-LEVEL STEERING CURRENTS.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 22.7N 116.3W 30 KT 35 MPH
12H 02/1800Z 23.2N 116.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 03/0600Z 23.5N 116.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 03/1800Z 23.7N 116.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 04/0600Z...DISSIPATED

$$
FORECASTER BROWN
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BULLETIN
TROPICAL DEPRESSION KIKO ADVISORY NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112013
200 AM PDT MON SEP 02 2013

...KIKO WEAKENS TO A TROPICAL DEPRESSION...
...EXPECTED TO BECOME A REMNANT LOW LATER TODAY...


SUMMARY OF 200 AM PDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...22.7N 116.3W
ABOUT 410 MI...655 KM W OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NNW OR 335 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES
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COC coordinates: 14.8n,58.5/59w? What does everyone else see?


And, there looks now to be convection firing south of there, directly over Barbados.

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Quoting 2172. moonlightcowboy:


Nice obs and reasoning, Kori.


You're the one who always says we should rely less on the models. :)
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Quoting 2140. KoritheMan:


I don't understand the reason for this, and I... don't think it's going to happen. And it's not because I want 97L to reach me either, before anybody says anything, XD.

But I mean, what's causing this? Increasing influence from the upper low over eastern Haiti? The 850 mb does not support such a poleward bend.



I mean seriously, Puerto Rico? 97L is way too far south to feel that weakness south of Bermuda. In addition, the trough over the western Atlantic, if there is one, is very weak. There is an upper low trailing a cold front near Toronto, but the upper support appears locked in too far north to allow for a significant southward propagation of the associated shortwave.

I would really expect some westward shifts in the guidance today, especially since 97L is not likely to develop anytime soon.


Nice obs and reasoning, Kori.
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Quoting 2169. 954FtLCane:
In all fairness to the models they have been trending NW throughout the day. It didn't happen all at once.

No they have been flopping N and E and flipping S and W alternating with each run
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Quoting 2168. KoritheMan:


To be fair, I wasn't saying a WNW track up Hispaniola is unreasonable; I even hypothesized a possible NW bend toward the Bahamas earlier today, and I still consider that a viable solution, at least for the next day or two. But no northwestward turn is going to occur nearly as quick as the models are saying, and that's all I'm saying, lol.

But the NHC does also mention the possibility of a more westward motion as well, and they also say near or over Hispaniola, not necessarily just over.


Gotta love this one...Euro dices it and runs the N half uptown (LOL!)...

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In all fairness to the models they have been trending NW throughout the day. It didn't happen all at once.
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Quoting 2165. daddyjames:


Just throwing it out there. All I know is that NHC has been pulling it up to the north for the past couple of discussions. So they may be seeing something we aren't at the moment.


To be fair, I wasn't saying a WNW track up Hispaniola is unreasonable; I even hypothesized a possible NW bend toward the Bahamas earlier today, and I still consider that a viable solution, at least for the next day or two. But no northwestward turn is going to occur nearly as quick as the models are saying, and that's all I'm saying, lol.

But the NHC does also mention the possibility of a more westward motion as well, and they also say near or over Hispaniola, not necessarily just over.
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2167. TXCWC
0Z UKMET depression or storm north of Cuba



In line with GFS GEM ensemble mean (18Z run) in terms of forecast location



18Z 15km Hi-Res GFS/Enkf


0Z 15km FIM 9



and current 06Z consensus guidance for general location



THE QUESTION WILL BE HOW ORGANIZED OR UNORGANIZED OF A SYSTEM WILL WE HAVE
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Quoting 2159. Kowaliga:
'Mornin' Kori........'ssup!


Looks like something is sitting there and doesn't want to go anywhere fast.
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Quoting 2163. KoritheMan:


That upper low and its attendant front is located north of Bermuda. There's no way 97L is going to feel that.


Just throwing it out there. All I know is that NHC has been pulling it up to the north for the past couple of discussions. So they may be seeing something we aren't at the moment.
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Quoting 2160. KoritheMan:


I'm not really sure we'll get a high that enormous over the Ohio Valley, but I'm also not willing to speculate on the upper flow pattern more than about five days in advance, and as we saw with Isaac, even that can be rather fickle.

I'm fairly confident it'll enter the Caribbean, however. I'm not afraid to go against the computers when what they're saying literally makes no sense, and has zero meteorological basis.

Okie dokie. Always fun trying to find a solution by starting at the answer, (or in this case something that might not be an answer) and trying to fill in the holes until you get to the beginning.
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Quoting 2162. daddyjames:


maybe it is these features - the high that has developed will strengthen, and 97L will follow the weakness caused by the stationary front. Just a guess.

A 1018 MB HIGH
PRESSURE CENTER DEVELOPED AROUND 0300 UTC NEAR 28N74W. FARTHER
EAST...AN UPPER-LEVEL TROUGH N OF 30N BETWEEN 58W-65W SUPPORTS A
STATIONARY FRONT THAT ENTERS THE REGION NEAR 30N60W TO 27N63W


That upper low and its attendant front is located north of Bermuda. There's no way 97L is going to feel that.
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Quoting 2155. KoritheMan:


Even if there were, that doesn't explain the immediate west-northwest to northwest motion being forecast by the 6z dynamical consensus. Satellite images clearly depict the wave axis to be centered around 14N 57W, moving due west. It's easy to spot on shortwave infrared images, even if it's not the most well-defined axis in the world.

What they're projecting literally makes no sense. And if their forecast for the initial motion is off (which it is -- badly), the entire forecast will be off in the extended range.


maybe it is these features - the high that has developed will strengthen, and 97L will follow the weakness caused by the stationary front. Just a guess.

A 1018 MB HIGH
PRESSURE CENTER DEVELOPED AROUND 0300 UTC NEAR 28N74W. FARTHER
EAST...AN UPPER-LEVEL TROUGH N OF 30N BETWEEN 58W-65W SUPPORTS A
STATIONARY FRONT THAT ENTERS THE REGION NEAR 30N60W TO 27N63W
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Quoting 2159. Kowaliga:
'Mornin' Kori........'ssup!



yo
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Quoting 2158. 954FtLCane:


I'm no expert by any means but these are the models that are speaking to us, anything is possible with computers as we've seen in the past.

Look at post 617 on this blog and see if that helps any. I just did some digging and found it


I'm not really sure we'll get a high that enormous over the Ohio Valley, but I'm also not willing to speculate on the upper flow pattern more than about five days in advance, and as we saw with Isaac, even that can be rather fickle.

I'm fairly confident it'll enter the Caribbean, however. I'm not afraid to go against the computers when what they're saying literally makes no sense, and has zero meteorological basis.
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'Mornin' Kori........'ssup!

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Quoting 2155. KoritheMan:


Even if there were, that doesn't explain the immediate west-northwest to northwest motion being forecast by the 6z dynamical consensus. Satellite images clearly depict the wave axis to be centered around 14N 57W, moving due west. It's easy to spot on shortwave infrared images, even if it's not the most well-defined axis in the world.

What they're projecting literally makes no sense. And if their forecast for the initial motion is off (which it is -- badly), the entire forecast will be off in the extended range.


I'm no expert by any means but these are the models that are speaking to us, anything is possible with computers as we've seen in the past.

Look at post 617 on this blog and see if that helps any. I just did some digging and found it
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We really need a well established, closed low level center to track, when you have models doing squiggly lines you don't whether to trust them or not.

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Lol..go to Texas? :P
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Quoting 2148. 954FtLCane:

any back door cold fronts possibly moving n towards the middle of the week moving in? I remember someone posting a graphic earlier today that showed high pressure moving in from the NE down towards the Ohio Valley and continue the same trek. I'm checking to see if thats the case.


Even if there were, that doesn't explain the immediate west-northwest to northwest motion being forecast by the 6z dynamical consensus. Satellite images clearly depict the wave axis to be centered around 14N 57W, moving due west. It's easy to spot on shortwave infrared images, even if it's not the most well-defined axis in the world.

What they're projecting literally makes no sense. And if their forecast for the initial motion is off (which it is -- badly), the entire forecast will be off in the extended range.
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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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