Lesser Antilles Disturbance 97L Still Disorganized

By: Dr. Jeff Masters , 2:34 PM GMT on September 03, 2013

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A tropical wave over the Lesser Antilles Islands (Invest 97L) is moving west-northwest at 10 mph, and is bringing sporadic heavy rain showers to the islands. Top sustained winds observed in the islands as of 10 am AST Tuesday were mostly below 15 mph. Heavy thunderstorm activity has been low since Monday, and is spread out, as seen on satellite loops. The thunderstorms are poorly organized, and there is no sign of a well-organized surface circulation. Martinique radar shows little evidence of rotation to the echoes, and no low-level spiral bands forming. Upper level winds are favorable for development, with wind shear a low 5 - 10 knots, and an upper-level anticyclone overhead. An area of dry air from the Saharan Air Layer (SAL) surrounds 97L and is interfering with development, though the the 12Z Tuesday balloon sounding from Guadeloupe near the center of 97L showed moist air through the entire depth of the atmosphere.


Figure 1. Latest satellite image of Invest 97L.

Forecast for 97L
Wind shear is expected to be low through Friday, and ocean temperatures will be warm, 29°C. The disturbance has not been able to generate enough thunderstorms to moisten the surrounding atmosphere much, and dry air may continue to slow down development over the next few days. The models take 97L to the west-northwest, bringing it near or over Puerto Rico or Hispaniola on Wednesday night. A track over the high mountains of Hispaniola would disrupt the circulation of 97L, forcing the storm to regroup on Thursday over the Southeast Bahamas and Turks and Caicos Islands. The best chance for development of 97L would appear to be on Friday, after the storm has finished its encounter with Hispaniola. This morning's 00Z run of the experimental GFDL ensemble--which produces 10 simulations with slightly varying initial conditions to create a plume of potential storm tracks--foresees that once 97L organizes into a tropical depression, it might take only two days for it to intensify into a hurricane to the north of Hispaniola. The wave will bring heavy rain showers to the Lesser Antilles islands on Tuesday and Wednesday, and this activity will likely spread to Puerto Rico, the Virgin Islands, the Dominican Republic, and Haiti on Wednesday and Thursday. These rains will be capable of causing life-threatening flash flooding and mudslides in mountainous regions of 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 over the Central Bahamas on Saturday. There will be a strong trough of low pressure along the U.S. East Coast this weekend, which will be capable of turning 97L to the north before the storm can hit the U.S. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC left the 5-day odds of formation of 97L at 50%, and 2-day odds at 20%. The Hurricane Hunters are on call to investigate 97L Wednesday afternoon. The flight scheduled for today will likely be cancelled. The Hurricane and Severe Storm Sentinel Mission, a 5-year field project utilizing two remotely crewed Global Hawk aircraft to overfly tropical storms and hurricanes, will have one of their aircraft investigate 97L today, and again on Wednesday. You can follow the progress of the aircraft using NASA's live-plane tracker map (Global Hawk AV6 is tail number NASA872, and Global Hawk AV1 is tail number NASA871.)

98L off the coast of Africa and a Yucatan Peninsula tropical wave
A tropical wave that emerged from the coast of Africa on Monday (Invest 98L) is expected to track northwest over the Cape Verde Islands. This course will take 98L into a region of ocean where historically, very few tropical cyclones have made the long journey across the Atlantic to affect North America. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC put the 5-day odds of development at 20%.

A tropical wave over Mexico's Yucatan Peninsula has a respectable area of heavy thunderstorms associated with it that is bringing heavy rains. This activity will push over the extreme Southern Gulf of Mexico's Bay of Campeche on Wednesday. The wave will have two days over water to develop before moving ashore on the Mexican coast between Veracruz and Tampico on Friday. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC put the 5-day odds of development at 30%, and 2-day odds at 20%.

Jeff Masters

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Has a bit of support from above.

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Quoting 359. FunnelVortex:


It's not 2 PM yet.

It is about 2pm eastern time already..waiting on two
Member Since: May 30, 2013 Posts: 0 Comments: 448
Quoting 358. MiamiHurricanes09:
Outflow boundaries are very much evident in this image you posted. Convection may begin to dwindle, but this time, due to dry air instrusion rather than lack of surface convergence due to the absence of a well-defined circulation as was occurring a few days ago.

97L has organized very nicely this afternoon though.


Yeah, but those boundaries are from old convection. New convection has fired in its place.
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364. IKE
F5 prevalent.

Who will be first to post the 2pm TWO?
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Member Since: March 12, 2013 Posts: 8 Comments: 13404
Quoting 344. WoodyFL:


Is that not a LARGE atmospheric envelope with 97L?
Member Since: September 18, 2010 Posts: 0 Comments: 5108
No northerly component here.

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Quoting 331. Drakoen:
Evidence that a surface circulation may be forming with 97L based on surface observations.



Does it appear that it is trying to reform - or collect itself - closer to Dominica, than to the south?
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Quoting 354. hurricanes2018:
where is the 2pm updte fom the national hurricane center


It's not 2 PM yet.
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Quoting 342. MississippiWx:
1km GOES East visible loop can now pick up 97L. It's updating every 6-8 minutes. It shows a low level center that is becoming increasingly organized with the low level clouds well out to the west moving in a WSW direction. Trades out in front may not be as detrimental as one would think.

Outflow boundaries are very much evident in this image you posted. Convection may begin to dwindle, but this time, due to dry air instrusion rather than lack of surface convergence due to the absence of a well-defined circulation as was occurring a few days ago.

97L has organized very nicely this afternoon though.
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Quoting 354. hurricanes2018:
where is the 2pm updte fom the national hurricane center

facebook them and see what is up :)
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Given 97L's current state of organization, I wouldn't be surprised to see a TD sometime in the next day or two. TS would probably come shortly thereafter, conditions being what they are in the Caribbean. After that, it's all about land and if it can avoid it or not.
Member Since: October 24, 2012 Posts: 0 Comments: 193
Quoting 352. Patrap:


Looks like that front will take it out to sea quickly if it moves NW as the models predict.
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where is the 2pm update fom the national hurricane center
Member Since: March 12, 2013 Posts: 8 Comments: 13404
Quoting 346. HurricaneHunterJoe:


Looks like that 14.5N spin wants to tuck under the convection just east and north of it......just my old eyes.


LOL..better than my inexperience eyes..
Member Since: August 19, 2006 Posts: 13 Comments: 14453
Member Since: July 3, 2005 Posts: 421 Comments: 127550
Quoting 321. mobhurricane2011:
Man it is hard for someone like myself who doesn't know anything about the tropics to tell what an invest or storm is doing. You got your its moving west camp, it's moving northwest camp. Then you got some saying it is looking better while some say its looking worse. I know alot of these post are from "trolls" and I think it's a crying shame that they come on here and purposely post false info for folks to see and possibly rely on. Just a shame. Thanks to the ones who are actually giving good info out


Trolls? Yep. You see them here. Especially during peak season, postseason, and preseason.
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Quoting 341. HurricaneHunterJoe:


It's all GOOD! Sit back and enjoy the ride.....wait til it gets a name!.....LOL
yeah I have witnessed that chaos here, lol. I know it's all good and I do enjoy the blog. Just not the ones who are purposely posting false info. I ignore them then they just keep coming. Oh well
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Member Since: July 3, 2005 Posts: 421 Comments: 127550
348. beell
Quoting 316. Levi32:


Yes I saw that, but again, that dry air, although present, is peripheral to the circulation.





But not isolated from it was all I was suggesting.
I have a date...with lunch.
:)
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Quoting 343. barbamz:


Two of them?? 97L and the wave closely behind?


from what I could tell, both are 97L..leaves a piece of energy behind..
Member Since: August 19, 2006 Posts: 13 Comments: 14453
Quoting 326. ncstorm:
97L


Looks like that 14.5N spin wants to tuck under the convection just east and north of it......just my old eyes.
Member Since: September 18, 2010 Posts: 0 Comments: 5108
Quoting 250. JeffMasters:
It's like a switch got turned on over 97L, and now it is starting to spin up. However, I'm seeing outflow boundaries on the convection on its north side, where dry air is getting ingested. Probably a 2-day 40% chance of development now.

Dr. M.


I agree. based on water vapor imagery and the sounding out of San Juan, PR that beell posted showing a large mid level dewpoint depression.
Member Since: October 28, 2006 Posts: 57 Comments: 29887
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Quoting 336. ncstorm:
12z Navgem








Two of them?? 97L and the wave closely behind?
Member Since: October 25, 2008 Posts: 51 Comments: 5645
1km GOES East visible loop can now pick up 97L. It's updating every 6-8 minutes. It shows a low level center that is becoming increasingly organized with the low level clouds well out to the west moving in a WSW direction. Trades out in front may not be as detrimental as one would think.

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Quoting 321. mobhurricane2011:
Man it is hard for someone like myself who doesn't know anything about the tropics to tell what an invest or storm is doing. You got your its moving west camp, it's moving northwest camp. Then you got some saying it is looking better while some say its looking worse. I know alot of these post are from "trolls" and I think it's a crying shame that they come on here and purposely post false info for folks to see and possibly rely on. Just a shame. Thanks to the ones who are actually giving good info out


It's all GOOD! Sit back and enjoy the ride.....wait til it gets a name!.....LOL
Member Since: September 18, 2010 Posts: 0 Comments: 5108
just experimental


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Quoting 320. barbamz:


Some glitch at least for me. Site is telling me: Cannot play media. Sorry, this media is not available in your territory. :(


That's weird. Normally the content is available outside the UK. The video was uploaded only a couple of hours ago, so perhaps it's still taking some time to get clearance for those outside? Hopefully it'll be avaible soon for those outside the UK!
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SYNOPSIS 2013090300

P25L … 97L (Down to 20%)
16N, 61W
700 hPa


ECMWF: Continues to be elongated SW-NE near the islands, but not splitting like a couple days ago.

GFS: Continues to track to northeast of the islands. Then becomes stationary and slowly weakens.

UKMET: Still stronger than the other models. Tracks farther northwest.

NAVGEM:

HWRF-GEN:



ECMWF -4.5 v700 120h
GFS -6.2 v700 120h
UKMET -4.5 v700 120h
NAVGEM ---- ---- ---h
HWGEN ---- ---- ---h


Member Since: July 3, 2005 Posts: 421 Comments: 127550
97L looking really good right now... the southern clouds had been lagging behind in terms of speed, but now they're accelerating towards the east. In fact, the spin in general is accelerating fairly rapidly. That should really help get convergence going. Also, that inflow to the south is impressive. The lower level clouds seem to arc out in a very nice, un-stretched or distorted path all the way around to PR. Really nice to look at.
Member Since: October 24, 2012 Posts: 0 Comments: 193
12z Navgem






Member Since: August 19, 2006 Posts: 13 Comments: 14453
Quoting 283. KEEPEROFTHEGATE:




Nice video Keeper!
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Member Since: July 3, 2005 Posts: 421 Comments: 127550
Quoting 319. ncstorm:
12z CMC got a hurricane approaching the islands..97L turns into a 957mb and tracks over Bermuda, remember CMC was the first to spot 97L





Why would the GEM take a weak system at 40W due north into a strong ridge?
Member Since: September 18, 2010 Posts: 0 Comments: 5108
GFDL ensemble still enthusiastic





Member Since: September 23, 2005 Posts: 14 Comments: 10875
Evidence that a surface circulation may be forming with 97L based on surface observations.

Member Since: October 28, 2006 Posts: 57 Comments: 29887
Quoting 321. mobhurricane2011:
Man it is hard for someone like myself who doesn't know anything about the tropics to tell what an invest or storm is doing. You got your its moving west camp, it's moving northwest camp. Then you got some saying it is looking better while some say its looking worse. I know alot of these post are from "trolls" and I think it's a crying shame that they come on here and purposely post false info for folks to see and possibly rely on. Just a shame. Thanks to the ones who are actually giving good info out


Well I don't think it's troll thing right now. Just a normal (and interesting) discussion about a not so simple system. :)
Member Since: October 25, 2008 Posts: 51 Comments: 5645
Quoting 317. wunderkidcayman:

It's like 97L is a zombie and zombies can really thrive in graveyards


LOL....I resemble that remark!....lol
Member Since: September 18, 2010 Posts: 0 Comments: 5108
Member Since: August 19, 2006 Posts: 13 Comments: 14453
327. beell
Subsidence on the back side of the ULL to the north?

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97L
Member Since: August 19, 2006 Posts: 13 Comments: 14453
I have a hard time see those highlighted links in Dr Masters blog, but here is the link about the Global Hawk Hurricane Missions as posted on his blog by him.

Link

Thanks again Doc!

Member Since: September 18, 2010 Posts: 0 Comments: 5108
324. wpb
have not watch a floater loop in a month and its september. last season i lived on that site. as csu called there two week forecast a BUST
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Storm Relative 1 km Geostationary Visible Imagery Loop

Click image for Loop

click Loop to ZOOM

Member Since: July 3, 2005 Posts: 421 Comments: 127550
Quoting 250. JeffMasters:
It's like a switch got turned on over 97L, and now it is starting to spin up. However, I'm seeing outflow boundaries on the convection on its north side, where dry air is getting ingested. Probably a 2-day 40% chance of development now.

Dr. M.


I disagree with the dry air statement, but the switch you are referring to is most likely 97L's ability to separate itself further from the disturbance/wave to the east. Time is dwindling for it to develop (until emergence in the Western Carib) since it should enter the graveyard tomorrow.
Member Since: Posts: Comments:
Man it is hard for someone like myself who doesn't know anything about the tropics to tell what an invest or storm is doing. You got your its moving west camp, it's moving northwest camp. Then you got some saying it is looking better while some say its looking worse. I know alot of these post are from "trolls" and I think it's a crying shame that they come on here and purposely post false info for folks to see and possibly rely on. Just a shame. Thanks to the ones who are actually giving good info out
Member Since: Posts: Comments:
Quoting 309. Envoirment:
Australia & New Zealand have their warmest winters on record.

BBC Weather Video

I wonder what implications that will have on the Australia region tropical cyclone season.


Some glitch at least for me. Site is telling me: Cannot play media. Sorry, this media is not available in your territory. :(
Member Since: October 25, 2008 Posts: 51 Comments: 5645
12z CMC got a hurricane approaching the islands..97L turns into a 957mb and tracks over Bermuda, remember CMC was the first to spot 97L



Member Since: August 19, 2006 Posts: 13 Comments: 14453
318. IKE
I see the outflow boundaries Dr. Masters is talking about.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting 312. RascalNag:
Isn't it funny how the moment 97L got in to the Eastern Caribbean graveyard, it decided to spin up?

It's like 97L is a zombie and zombies can really thrive in graveyards
Member Since: June 13, 2009 Posts: 2 Comments: 11029

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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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