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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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: 11023
Quoting 311. beell:
A column is almost always going to be saturated near the core of an LLC.

Sometimes a look at a source region that might be ingested by the circulation can be interesting. Not to say 97L is not looking better.

San Juan Morning Sounding





Yes I saw that, but again, that dry air, although present, is peripheral to the circulation. If the thunderstorms developing near Gaudeloupe at 12z truly collapsed in the last hour due to mid-level dry air, we should have seen it on that sounding, in my opinion.

In the SE quad, where there is no significant convection, the Barbados sounding is also very moist.

Member Since: November 24, 2005 Posts: 635 Comments: 26547
97 convection even to the south side wow john hope rule broken? maybe not. back in john hopes day with limited recon ext 97 might of been declared a depression a few days ago .the southern leewards all had west winds. that was the cue.
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Quoting 291. hurricanes2018:
we say goodbye to invest 97L ONLY going to be a littie rain storm.
lets hope so!
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Quoting 306. Levi32:


It is and has been 97L's center. The wave to the northeast is robbing some low-level convergence from it, but itself does not have a low center.


Quoting 306. Levi32:


It is and has been 97L's center. The wave to the northeast is robbing some low-level convergence from it, but itself does not have a low center.
Yes... I was not talking about the wave to the NE...lol Just the wave to the west of the Lesser ant.
Member Since: August 28, 2008 Posts: 0 Comments: 293
Isn't it funny how the moment 97L got in to the Eastern Caribbean graveyard, it decided to spin up?
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311. beell
A column is almost always going to be saturated near the core of an LLC.

Sometimes a look at a source region that might be ingested by the circulation can be interesting. 97L is looking better!

San Juan Morning Sounding



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310. IKE
Quoting clwstmchasr:



Still love your avatar. Greatest Rock and Roll band of all time.
Yes sir.

Bad thunderstorm moving through here. Branches down in my yard. One just missed my water pump.


Member Since: June 9, 2005 Posts: 23 Comments: 37858
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.
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Quoting 284. Abacosurf:
Yes... Much healthier. Now getting a nice S signature to it as well. You'll see.


It sure does...lets see if it continues.
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Quoting 300. Abacosurf:
Levi. Do you see the center below 15N as the primary? Looks as if the northern bands are pulling in towards that now after the outflow boundary collapsed on the north side.
I see the center below 15N for sure?? You?


It is and has been 97L's center. The wave to the northeast is robbing some low-level convergence from it, but itself does not have a low center.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting 226. Chucktown:


If the 12Z GFS is correct (not looking at 97L) the east coast trough sharpens just along 75 West or so and really doesn't "leave" until next Tuesday. I don't think this makes it into the Bahamas.

Link


I agree however the Euro is the only model really handling 97L correctly. It is obivious 97L is not being pegged correctly by the NHC.
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97L look better since the massive breakdown 2 nights ago.
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its look like invest 97L IS MOVING WEST!
Member Since: March 12, 2013 Posts: 8 Comments: 13389
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 see a lot of those arc clouds you've spoken on.
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Quoting 293. Levi32:


There's dry air on the outskirts of every tropical system. If that dry air was actually getting ingested into the circulation on the northern side, I think we would have seen it manifested in the mid levels on the Guadeloupe sounding, which is the location where those convective cells were developing around 12z.
Levi. Do you see the center below 15N as the primary? Looks as if the northern bands are pulling in towards that now after the outflow boundary collapsed on the north side.
I see the center below 15N for sure?? You?
Member Since: August 28, 2008 Posts: 0 Comments: 293
Member Since: July 3, 2005 Posts: 420 Comments: 127550
Quoting 293. Levi32:


There's dry air on the outskirts of every tropical system. If that dry air was actually getting ingested into the circulation on the northern side, I think we would have seen it manifested in the mid levels on the Guadeloupe sounding, which is the location where those convective cells were developing around 12z.




Trade winds are his biggest enemy atm, dry air is present without a doubt.
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296. IKE

Quoting clwstmchasr:


Gee, I wonder who you are talking about:)
lol
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting 270. MahFL:
Seems like the Dr. is desperate for a hurricane, lol.


I believe Dr Masters states his thoughts/facts as he sees them!
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Quoting 276. 7544:
97l beginnig to look like a dounut at this hour lets see if it will fill in .


Donut = annular
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Quoting 281. MahFL:
The dry air is to the north of Guadeloupe.



There's dry air on the outskirts of every tropical system. If that dry air was actually getting ingested into the circulation on the northern side, I think we would have seen it manifested in the mid levels on the Guadeloupe sounding, which is the location where those convective cells were developing around 12z.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Member Since: July 3, 2005 Posts: 420 Comments: 127550
we say goodbye to invest 97L ONLY going to be a littie rain storm.
Member Since: March 12, 2013 Posts: 8 Comments: 13389
Member Since: July 3, 2005 Posts: 420 Comments: 127550
288. 7544
Quoting 286. unknowncomic:
Track for 97L may shift west.


agree
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Just got back from my first classes. Seems like the 14.2N, 62.8W spin I saw is in fact taking over the system. Now it's more at 14.3N, 63.3W. Moving very close to due west but has a tiny bit of northern motion.
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Track for 97L may shift west.
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Quoting 277. bryanfromkyleTX:


GREAT!!!! NO STORM!!!



most likely not, that wont lessin the impacts on the islands however.
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Quoting 265. WoodyFL:




it does
Yes... Much healthier. Now getting a nice S signature to it as well. You'll see.
Member Since: August 28, 2008 Posts: 0 Comments: 293


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Quoting 259. WoodyFL:



He was insisting Dorian was moving due west the entire time, contrary to everyone on the blog




Most of the models had Chantal moving west so it wasn't much of an issue



There wasn't a day he didn't write Dorian was moving due west and would be a Caribbean cruiser.




Your Dorian track is disingenuous.........it tracked actually west just off P.R and into the Southern Bahamas as a open wave and turned north just off the Florida east coast as a TD. THAT STRAIGHT LINE CONNECTION BELIES THE ACTUAL FACTS!
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281. MahFL
The dry air is to the north of Guadeloupe.

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Same fun every year XD
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Quoting 221. Patrap:

Global Hawks current position
Current Altitude, is 50K ft
Member Since: July 3, 2005 Posts: 420 Comments: 127550
Quoting 268. wunderkidcayman:

That isn't true yes I did say Dorian was moving W bound most of time which it did and travel through the greater Antilles and came out near the E coast of Cuba then traveled N bound toward E coast of Florida



I saved the quotes if you want to see them. Everyone was saying WNW and you were saying due west. on every system that popped up. Look I don't care where you want to forecast something. We all do it. Sometimes we're right and sometimes we're wrong.
But don't call someone a liar and say you didn't say something.
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Quoting 264. chrisdscane:
better banding on south side but 97l realy needs some CDO, im afraid that wont happen due to the trade wind flow out of the east, this may make a run at a name before interacting with the islands.


GREAT!!!! NO STORM!!!
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276. 7544
97l beginnig to look like a dounut at this hour lets see if it will fill in .
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275. MahFL
The shear is supposed to be 7 kts but it looks a bit higher than that, more like 20.
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models have the right idea with a recurve regardless of strenth this will likely miss the U.S and be absorbed into the trough
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Quoting 267. bluewaterblues:
I am going on record to say I am in Wunderkidcaymans camp on this one. I think he has presented a good analysis. With the system still rather elongated the models could truly be off with still no truly defined LLC....we shall see

Yes thank you and yes as I said just wait and watch

Member Since: June 13, 2009 Posts: 2 Comments: 11023
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.


Are you sure it's dry air? The 12z Guadeloupe sounding was all but saturated. 700mb relative humidity and 500mb relative humidity were both 90%. I think the outflow boundaries associated with the cells in the NW quadrant are due to low-level divergence inducing sinking as the trade winds accelerate just to the west of there in the Caribbean graveyard.

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270. MahFL
Seems like the Dr. is desperate for a hurricane, lol.
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269. Skyepony (Mod)
Toraji



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Quoting 259. WoodyFL:



He was insisting Dorian was moving due west the entire time, contrary to everyone on the blog




Most of the models had Chantal moving west so it wasn't much of an issue



There wasn't a day he didn't write Dorian was moving due west and would be a Caribbean cruiser.



That isn't true yes I did say Dorian was moving W bound most of time which it did and travel through the greater Antilles and came out near the E coast of Cuba then traveled N bound toward E coast of Florida
Member Since: June 13, 2009 Posts: 2 Comments: 11023
I am going on record to say I am in Wunderkidcaymans camp on this one. I think he has presented a good analysis. With the system still rather elongated the models could truly be off with still no truly defined LLC....we shall see
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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.