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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EP, 11, 2013090200, , BEST, 0, 223N, 1160W, 45, 1000, TS, 34, NEQ, 60, 50, 30, 40, 1009, 180, 20, 0, 0, E, 0, , 0, 0, KIKO, M,
Member Since: July 21, 2011 Posts: 83 Comments: 7167
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.

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1553. ncstorm
18z HWRF

Member Since: August 19, 2006 Posts: 13 Comments: 15699
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
Member Since: September 2, 2009 Posts: 130 Comments: 21194
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:

Vort definitely looks like it consolidated further east in the past few hours.
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Quoting 1545. ncstorm:
holy crap!!


Ryan Maue ‏@RyanMaue

Upgraded HWRF 18z more intense than GFDL with close to major hurricane in 66 hrs for Invest 97L pic.twitter.com/IkaVxyeIpO
Umm if that were to occur it would be rapid intensification.
Member Since: June 30, 2013 Posts: 12 Comments: 8454
1549. JRRP
Quoting sunlinepr:


Le falta el palito a la n

ññññññññññññ

lol
Member Since: August 16, 2007 Posts: 0 Comments: 5986
Quoting 1537. wunderkidcayman:

00Z models should be further S and W
Quoting 1540. JRRP:

Nope just a smother ride WNW toward Haiti and Cuba hmm interesting we need to watch this though I think it will keep on flip flopping until we get a TD or a TS
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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?

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Quoting 1541. unknowncomic:
Fanning caused by shear or outflow?


Outflow. Anticyclone over it.
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1545. ncstorm
holy...!!


Ryan Maue %u200F@RyanMaue

Upgraded HWRF 18z more intense than GFDL with close to major hurricane in 66 hrs for Invest 97L pic.twitter.com/IkaVxyeIpO
Member Since: August 19, 2006 Posts: 13 Comments: 15699
Quoting 1531. wxgeek723:
My theory on the slow hurricane season?
SOMEONE stole the names....
Wow....We need Brutus as cat.5 in the CATL.
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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:
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Quoting 1529. daddyjames:


Doesn't the HWRF and GFDL incorporate data from the GFS?
Yes they are all NCEP models. I think the FIM also incorporates data from the GFS.
Member Since: June 30, 2013 Posts: 12 Comments: 8454
Fanning caused by shear or outflow?

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1540. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5986
Quoting 1531. wxgeek723:
My theory on the slow hurricane season?
SOMEONE stole the names....
BRUTUS. That's the tough guy from "Popeye."
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Quoting 1514. HurricaneHunterJoe:


Is that a feeder band in black on the satellite?........j/k....couldn't resist.
Feeder band.? What about shear breaking the clouds.
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Quoting 1532. JRRP:

00Z models should be further S and W
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What I see:-

1.) Convection has waned a bit, but there is still plenty with D-Max right around the corner.

2.) Despite the waning Convection, the already large wind field of the storm has grown a bit over the last few hours and will continue to grow as it begins to feed off moisture from the storm to it's south west and eventually merges with it.

3.) There is a bit of dry air to the south of 97L but that pocket of dry air is surrounded by 97L, The SW tropical wave, the very vigorous mid/upper level low out ahead of 97L and the huge plume of moisture between Cuba and the Yucatan.

4.) There is A LOT LOT LOT of rotation in the Caribbean and Gulf of Mexico associated with several different systems - this tells me that there is a lot of instability in the atmosphere and I think there is a lot of potential for some very significant development of 97L if it manages to move directly west and south of Hispaniola.

To do this it will need to develop a strong anti-cyclone that would allow it to largely ignore the weakness presented to it by the High pressure to 97L's north, which could very well happen.

5.) This is a very interesting storm, and there is so much going on around it with all of these systems, this is going to be quite entertaining to track with all of these pieces interacting with each other. 


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IT IS A GOOD THING THAT 97L DID NOT STRENGHEN. BEING STATIONARY IT WOULD HAVE CAUSED SRIOUS FLOOD DAMAGE TO THESE ISLANDS WHICH HAVE RECENTLY SEEN QUITE A BIT OF RAINE
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Quoting 1507. Bluestorm5:
Tornado reported in Illinois and NWS radar in Chicago is down... oh boy.


The storm and possible tornado are in the outer parts of the Chicago metro. Another line building to the north though with a pronounced anvil cloud on the western edge.
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Quoting 1487. MAweatherboy1:
DMIN has been pretty hard on it. So far no signs of a rebound; quite the opposite in fact, with convection declining faster with each new frame.

We'll see Dmin impacts, I expect, until about 11 p.m. our time [which is currently the same as the ECar, IIRC]
Member Since: October 25, 2005 Posts: 19 Comments: 22322
1532. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5986
My theory on the slow hurricane season?
SOMEONE stole the names....
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Quoting 1516. MAweatherboy1:

Link

Just watch the loop, convection has warmed considerably.


That's normal for these type of systems in their early formative stages.
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Quoting 1461. GTstormChaserCaleb:
Interesting HWRF, GFDL, and GFS agreeing on track.



Doesn't the HWRF and GFDL incorporate data from the GFS?
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Keep dreaming hwrf that is absolutely not happening that quick.
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Yikes!

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
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Quoting 1508. unknowncomic:
This will make Florida wishcasters happy.




its going right overe lake O
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
Quoting 1522. prcane4you:
El palito does'nt exist in english.That's why.You got it boricua?


Pero como soy boricua, si lo uso cuando hablo... ;)

Not a single drop of rain around.... Big group of friends going to Caja de muertos in the morning...

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Quoting 1499. kmanislander:


That low has been sitting there forever. The steering is very weak and 97L does not appear to be going anywhere in a hurry. Those models calling for a track over Hispaniola must have concluded that 97L will follow the weakness being created by the ULL but only time will tell. All depends if 97L and the ULL are both moving at a snails pace otherwise the ULL will retrograde and a high will build in to the N of Hispaniola and force 97L or whatever it becomes to the W.

All guess work for now.






Thanks, Kman. Nice discernment as usual, friend. :)
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Quoting 1516. MAweatherboy1:

Link

Just watch the loop, convection has warmed considerably.
The key is keeping the circulation going, I believe.
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Quoting 1503. sunlinepr:


Le falta el palito a la n

ññññññññññññ
El palito does'nt exist in english.That's why.You got it boricua?
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Wow looking at 15 minute satellite frames won't predict the outcome of 97L geez. It's like your spoofing it right now. It's dmin hello. Some folks also didn't see it earlier anyways too!!! 81w
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Quoting 1517. FunnelVortex:


Speaking of wishcasters, in a couple months I'll be wishcasting winter storms again, I may start early if the hurricane season doesn't pick up.
I would welcome that because it means more $ for Florida tourism.(Sorry Cold weather disdainers)
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97L is beginning to finally consolidate convection over its low level center as seen in latest satellite imagery this development of new convection will help c solid ate the surface center and develop organized convection.
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Quoting 1478. Walshy:


Nice. Breaking Bad is on at 9 the blog should be a ghost town then.


I wonder what happens to Jessie tonight!

Now, back to Day's of Our Lives, 97L
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Quoting 1508. unknowncomic:
This will make Florida wishcasters happy.



Speaking of wishcasters, in a couple months I'll be wishcasting winter storms again, I may start early if the hurricane season doesn't pick up.
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Quoting 1506. RyanSperrey:

The storm is holding up very well through D-min, I'm not sure what you're speaking of but it still has a ton of widespread convection.

Link

Just watch the loop, convection has warmed considerably.
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invest 97L be a rain storm that it for the next 72 hours.. no tropical storm at all.
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Quoting 1440. sunlinepr:
Next wave looks like it could merge with 97L, if it keeps stationary....



Is that a feeder band in black on the satellite?........j/k....couldn't resist.
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1513. Walshy
Quoting FunnelVortex:


What's "it" and why shouldn't I quote?


I have those people who use caps and downcasting in the same sentence during DMIN on ignore.

97L is doing much better than some of our previous invests this year during DMIN. It's not on the verge of disappearing and kept its probability formation from the NHC for once.
Member Since: May 17, 2009 Posts: 2 Comments: 904
Satellite switched over to Night Visible mode:

Member Since: June 30, 2013 Posts: 12 Comments: 8454
AL, 97, 2013090200, , BEST, 0, 140N, 606W, 30, 1008, LO, 0, , 0, 0, 0, 0,
Member Since: July 21, 2011 Posts: 83 Comments: 7167
00z Best Track.

AL, 97, 2013090200, , BEST, 0, 140N, 606W, 30, 1008, LO
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Quoting 1505. Tropicsweatherpr:
18z HWRF.



Impressive....
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This will make Florida wishcasters happy.

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Tornado reported in Illinois and NWS radar in Chicago is down... oh boy.
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Quoting 1487. MAweatherboy1:
DMIN has been pretty hard on it. So far no signs of a rebound; quite the opposite in fact, with convection declining faster with each new frame.

The storm is holding up very well through D-min, I'm not sure what you're speaking of but it still has a ton of widespread convection.
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18z HWRF.

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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.