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 1559. farhaonhebrew:
no importa ' the name Hurricanes come from the spanish word Hurac�n...named by the western indians... so cual es el problema con hablar espa�ol..la mayoria de las islas y tierras afectadas son hispano parlantes..inclusive en la costa este de Estados Unidos..
Lee mis labios(Read my lips) Yo no dije eso (I don't said that) NO cambies lo que dije (Dont change what I said and stop thinking the wrong way,Entendiste? Did you understand my friend?
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Quoting 1594. GTstormChaserCaleb:
And to add if this were to be a major hurricane going over the mountainous terrain of Hispaniola it would almost have little to no effect disrupting it completely, maybe knocking it down to a minimal hurricane or tropical storm, definitely one to watch as we head into this week as the models seem to want to move it fast.
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Quoting 1598. flsky:

Spin over Haiti??
CCKW or TW moving towards 97L, the spark for this thing to take off that the models are seeing?
Member Since: June 30, 2013 Posts: 12 Comments: 8429
Quoting 1592. wxgeek723:

Yeah but that was July.
Let's not use that excuse..I remember back in 010 they showed Fiona running into S.C as a cat 5.The end result? a weak sheared tropical storm....They showed Isaac last year plowing into NOLA as a 4..And they were in August..

GTstormChaserCaleb "Give me a break"
Member Since: August 14, 2010 Posts: 10 Comments: 17081
Quoting 1563. sar2401:

Why would you hate it when people say this? It's the absolute truth. Until there's a decent COC, all the models are initializing off bogus vortexes, and none of them are likely to be right. Even worse are these ridiculous intensity forecasts showing a cat 2 (Edit: Now cat 3 and cat 4) hurricane when we don't even have a TD yet. I know the blog needs model to keep occupied, but anyone who puts any faith in these models is foolish.
That's just how I am as a person. :)

I seriously don't understand why a majority of the blog seems to have trust issues when it comes to forecast models. Regardless of the circulation being broad or consolidated, if the plots are pointing towards a certain direction, chances are, that it goes towards that direction. It's pretty obvious that 97L will be impacting the Greater Antilles, regardless of where the surface circulation is located. That's just the synoptic circumstance that the system is currently finding itself within. An initialization that is 2 degrees too far east, west, north, or south from where the circulation truly consolidates isn't going to change the track from a landfall on the Hispaola coast, to a landfall in Greenland is it? The fact that the system isn't a tropical depression right now...at this exact moment...doesn't really mean much at all to me, honestly. The point of the intensity models is give you a proper outlook on the type of conditions that the system will find itself encountering in the future. If you don't believe that a hurricane is possible, as a matter of fact, likely, when environment conditions constitute 29 sea surface temperatures, less than 10 knots of upper-level winds, and a moist mid-level environment, then I don't know what to tell you. It's pretty obvious that the conditions are there...and there really is no reason for 97L not to take advantage of them.
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Quoting 1591. Patrap:
Guidance converging..as consensus grows more confident downstream.










It also shifted a little farther south at 0Z
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Quoting 1590. washingtonian115:
Yeah...those same models also showed Chantal and Dorian going into the U.S as majors...(fast forward)we still have yet to get a hurricane...LOL GMAB...
Does GMAB stand for "Grab me a beer?"
Member Since: June 30, 2013 Posts: 12 Comments: 8429
1598. flsky

Spin over Haiti??
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Quoting 1591. Patrap:
Guidance converging..as consensus grows more confident downstream.







5 days!?!? and it's already north of Cuba O_o
Member Since: June 30, 2013 Posts: 12 Comments: 8429
man FL need too keep a close eye on 97L evere one living around lake O needs too keep vary close eye on this
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
This shows a very moist environment around it


Link
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Quoting 1570. hydrus:
That is a dangerous spot for a hurricane. Especially where Miami is concerned. This would be bad for the Dominican Rep. and Haiti. Right by where David hit as a cat-5 in 1979.

And to add if this were to be a major hurricane going over the mountainous terrain of Hispaniola it would almost have little to no effect disrupting it completely, maybe knocking it down to a minimal hurricane or tropical storm, definitely one to watch as we head into this week as the models seem to want to move it fast.
Member Since: June 30, 2013 Posts: 12 Comments: 8429
97L is and will stay east of the Lesser Antilles for a while
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Quoting 1590. washingtonian115:
Yeah...those same models also showed Chantal and Dorian going into the U.S as majors...(fast forward)we still have yet to get a hurricane...LOL GMAB...
Yeah but that was July. 
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1591. Patrap
Guidance converging..as consensus grows more confident downstream.







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Yeah...those same models also showed Chantal and Dorian going into the U.S as majors...(fast forward)we still have yet to get a hurricane...LOL GMAB...
Member Since: August 14, 2010 Posts: 10 Comments: 17081
18Z GFDL progs a near perfect thread thru Windward pass; dumps it in the gulf stream "spa" with Miami in the crosshairs approaching Cat 2.

Member Since: September 8, 2005 Posts: 0 Comments: 349
Quoting 1568. CaribBoy:


LOL what a joke!! 14N 60W....
The seesaw wave.
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It's not moving, don't have a coc..Throw out the models..This is the season we have endured..
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1586. sar2401
Quoting unknowncomic:
Fanning caused by shear or outflow?


I believe it's entraining quite a bit of dry air from its north. It shows up pretty clearly on water vapor loops.
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Intensity models showing no signs of backing down.

LGEM forecasting a category 4, SHIPS forecasting a category 3.

V (KT) LAND 30 33 37 41 46 57 67 78 86 89 96 99 101
V (KT) LGE mod 30 31 33 36 40 49 63 78 94 106 114 115 113.. NO WAY!! I DO NOT SEE IT HAPPERN
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Quoting 1578. MiamiHurricanes09:
ftp://ftp.nhc.noaa.gov/atcf/stext/13090200AL9713_ ships.txt



thanks
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
The 2013 Hurricane Season as it stands today.


6 Named Storms
0 Hurricanes
0 Major Hurricanes


Current Personal Forecast (Original Forecast)-
16 Named Storms (18 Named Storms)
7 Hurricanes (11 Hurricanes)
3 Major Hurricanes (5 Major Hurricanes)

As the 2013 Hurricane Season stands today, September 1st, we have yet to have a Hurricane Form in the Atlantic Basin. We are 9 days away from the climatological peak of the Hurricane season, and have the potential to break the record for the latest first hurricane of the Hurricane Season, this being mainly due to the large stable air mass that has been stuck in the Tropics during the season, mainly due to the Negative Atlantic Tripole fizzling and becoming less defined before the season started. Though the season has only had 6 Named Storms, it still has the potential to be deadly and destructive. No one, anywhere on the coastlines of North America and the Caribbean Islands should be writing the season off as a dud.

It Only Takes One

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Quoting 1543. JLPR2:
Although it's still a bit elongated 97L improved in structure in the past 3hrs, but convergence is still missing meaning the LLC isn't that solid, though upper divergence is excellent. Seems the place to look for new convection is 60W.

850mb:


700mb:


500mb:
Wow.......Ada Monzon va a perder su trabajo.Aprendiste con Israel Matos?
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Im shocked the Intensity models havent backed down yet
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1580. ncstorm
Just hypothetically speaking but if and I mean IF this thing does ramp up to a major, talk about an odd season..late on producing a hurricane but the first one out the gate is a major??..
Member Since: August 19, 2006 Posts: 13 Comments: 15666
1579. Patrap


Get Gonzo and Miss Piggy prepped and on the ramp in 30.

Someone get a pot o Java percolating.

Keeper, get Gro on the Horn.

Were going to Blob-Con Yellow







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Quoting 1567. wunderkidcayman:

Can you find and post me the text file for the SHIPs thanks
Quoting 1565. Tazmanian:




what dos it have for shear?


and what dos it have for the ch of RI?
ftp://ftp.nhc.noaa.gov/atcf/stext/13090200AL9713_ ships.txt
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Quoting 1554. GatorWX:
So essentially it hasn't moved all day. It really doesn't look that good right now compared to earlier. Kind of showing its true colors so to speak.



Mostly due to that huge ULL ripping its N edge.... causing it to move convection to the SE.... now it is also begining to interact with the merging wave.... But what a big WVapor mess in the area....

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Quoting 1571. MiamiHurricanes09:
Not really. If 97L is able to become a tropical cyclone, it should have no problems intensifying to that point given the environmental conditions present in the Caribbean...given it doesn't intersect Hispañola.
...sarcasm flag
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1575. GatorWX
To me though, it looks like it's going to take some time. See y'all later.
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SHIPS is showing an almost perfect environment for 97L, 29C+ SSTs, and shear under 10kts. RH values a little dry but not enough to kill it. Almost certainly far to aggressive though. At least we should hope...
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1573. JLPR2
Quoting 1554. GatorWX:
So essentially it hasn't moved all day. It really doesn't look that good right now compared to earlier. Kind of showing its true colors so to speak.



Quoting 1551. MAweatherboy1:

Vort definitely looks like it consolidated further east in the past few hours.


These two comments go together well.

The system seems to be getting stacked around 60W, vorts also seem stronger with the 500mb level finally showing some yellows. 97L should enter D-max with a better structure which could help it to finally start developing.

Of course there is the E-Caribbean graveyard problem, so we'll see.
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1572. GatorWX
After seeing mlc's rgb, it may have a good dmax and look a lot better in the am, but for whatever reason, I'm pretty doubtful. Structurally it's there, but I doubt it'll put on a bout like it did today. We'll see. Looks like quite a bit more shear affecting it. I just got in and I'm going right back out after I throw down some blackened grouper, gotta love summer black grouper!
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Quoting 1558. wxgeek723:

I think those are a little dubious at this point :b 
Not really. If 97L is able to become a tropical cyclone, it should have no problems intensifying to that point given the environmental conditions present in the Caribbean...given it doesn't intersect Hispañola.
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1570. hydrus
Quoting 1508. unknowncomic:
This will make Florida wishcasters happy.

That is a dangerous spot for a hurricane. Especially where Miami is concerned. This would be bad for the Dominican Rep. and Haiti. Right by where David hit as a cat-5 in 1979.

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Quoting 1561. stoormfury:
97L WILL KICK START WHEN IT GET A JUMP FROM THE DISTURBANCE TO THE SOUTH EAST. IT APPEARS THE TWO WILL SOON MERGE




can you plzs stop yelling
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
Quoting 1532. JRRP:


LOL what a joke!! 14N 60W....
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Quoting 1552. MiamiHurricanes09:
Intensity models showing no signs of backing down.

LGEM forecasting a category 4, SHIPS forecasting a category 3.

V (KT) LAND 30 33 37 41 46 57 67 78 86 89 96 99 101
V (KT) LGE mod 30 31 33 36 40 49 63 78 94 106 114 115 113

Can you find and post me the text file for the SHIPs thanks
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Quoting 1554. GatorWX:
So essentially it hasn't moved all day. It really doesn't look that good right now compared to earlier. Kind of showing its true colors so to speak.

It literally just went through D-Min, D-Max is soon and we will undoubtedly see a ton of convective blow up, especially with the Dry air to it;s south shrinking and the second wave behind 97L will moisten the environment even further for 97L. 

This will certainly become a storm, good chance of a Hurricane too. 
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Quoting 1552. MiamiHurricanes09:
Intensity models showing no signs of backing down.

LGEM forecasting a category 4, SHIPS forecasting a category 3.

V (KT) LAND 30 33 37 41 46 57 67 78 86 89 96 99 101
V (KT) LGE mod 30 31 33 36 40 49 63 78 94 106 114 115
113




what dos it have for shear?


and what dos it have for the ch of RI?
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
A little farther south tonight


Link
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1563. sar2401
Quoting MiamiHurricanes09:
Not buying it...at all. Virtually impossible that 97L becomes a hurricane by the time it reaches Puerto Rico's longitude. That type of intensity would be the only reason it moves that poleward.

Even though I hate when people say this, until a surface circulation consolidates, model runs are a bit of a shot in the dark...although I am lenient towards a Jamaica/Cuba event.

Why would you hate it when people say this? It's the absolute truth. Until there's a decent COC, all the models are initializing off bogus vortexes, and none of them are likely to be right. Even worse are these ridiculous intensity forecasts showing a cat 2 (Edit: Now cat 3 and cat 4) hurricane when we don't even have a TD yet. I know the blog needs model to keep occupied, but anyone who puts any faith in these models is foolish.
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CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
0028 UTC MON SEP 2 2013

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL972013) 20130902 0000 UTC

...00 HRS... ...12 HRS... ...24 HRS... ...36 HRS...
130902 0000 130902 1200 130903 0000 130903 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 14.0N 60.7W 14.1N 62.2W 14.3N 63.5W 14.6N 65.0W
BAMD 14.0N 60.7W 14.0N 62.4W 14.2N 64.2W 14.5N 66.1W
BAMM 14.0N 60.7W 13.9N 62.2W 14.0N 63.6W 14.2N 65.1W
LBAR 14.0N 60.7W 14.2N 62.8W 14.5N 64.9W 14.9N 67.2W
SHIP 30KTS 37KTS 46KTS 57KTS
DSHP 30KTS 37KTS 46KTS 57KTS

...48 HRS... ...72 HRS... ...96 HRS... ..120 HRS...
130904 0000 130905 0000 130906 0000 130907 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 15.2N 66.5W 17.2N 70.3W 19.4N 74.6W 20.8N 78.1W
BAMD 15.0N 68.1W 16.9N 72.3W 19.0N 76.6W 20.7N 79.8W
BAMM 14.6N 66.8W 16.3N 70.6W 18.2N 74.6W 19.7N 77.8W
LBAR 15.6N 69.5W 18.0N 74.2W 21.0N 78.3W 24.1N 79.9W
SHIP 67KTS 86KTS 96KTS 101KTS
DSHP 67KTS 86KTS 96KTS 101KTS

...INITIAL CONDITIONS...
LATCUR = 14.0N LONCUR = 60.7W DIRCUR = 270DEG SPDCUR = 11KT
LATM12 = 14.0N LONM12 = 59.0W DIRM12 = 270DEG SPDM12 = 7KT
LATM24 = 14.0N LONM24 = 57.2W
WNDCUR = 30KT RMAXWD = 70NM WNDM12 = 30KT
CENPRS = 1008MB OUTPRS = 1011MB OUTRAD = 200NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM


NO WAY WINDS OVER 100 MPH.. I DO NOT THINK SO!
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97L WILL KICK START WHEN IT GET A JUMP FROM THE DISTURBANCE TO THE SOUTH EAST. IT APPEARS THE TWO WILL SOON MERGE
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Quoting 1553. ncstorm:
18z HWRF



I think that's pretty tiny. Don't think it's right.
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Quoting 1522. prcane4you:
El palito does'nt exist in english.That's why.You got it boricua?
no importa ' the name Hurricanes come from the spanish word Huracn...named by the western indians... so cual es el problema con hablar espaol..la mayoria de las islas y tierras afectadas son hispano parlantes..inclusive en la costa este de Estados Unidos..
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Quoting 1552. MiamiHurricanes09:
Intensity models showing no signs of backing down.

LGEM forecasting a category 4, SHIPS forecasting a category 3.

V (KT) LAND 30 33 37 41 46 57 67 78 86 89 96 99 101
V (KT) LGE mod 30 31 33 36 40 49 63 78 94 106 114 115 113
I think those are a little dubious at this point :b 
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Wow. 115 knots.

V (KT) LGE mod 30 31 33 36 40 49 63 78 94 106 114 115 113
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Quoting 1547. moonlightcowboy:
Kman, it's fairly obvious in the RGB Loop below that there is quite a circ, albeit a large circ, with low level inflows fully surrounding a coc. What's your take on why it's either not tightening or getting the tropical engine going? Not at the sfc? Not enough moisture at the sfc? What am I missing?


It's been doing weird stuff today I'd say its anybody's guess really
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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.