Lesser Antilles Disturbance 97L Still Disorganized

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

Share this Blog
41
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 717 - 667

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18Blog Index

Quoting 712. TomTaylor:
?

-PDO AMO and neutral to weak La Nina conditions are arguably the most favorable conditions you could ask for in the Atlantic. Multi-year La Ninas can become a problem, but we haven't been in a full blown multi-year La Nina. -PDO and neutral to near Nina conditions may help partially explain the global downturn in activity, but not the Atlantic's.


Clearly not always, seeing as 2013 is the current state it's in. What I'm trying to say is that there's no focus of heat in our basin due to warm water in the northern latitudes of the Atlantic and near the poles. Also, I'm aware we haven't been in a true La Nina state since 2010, I don't believe we've recorded a multi-year neutral phase which is interesting, I'm just comparing that the effects might be similar to what we saw in the 70s.
Member Since: Posts: Comments:
Quoting 713. Tazmanian:
the mode runs are doing a vary poor job with 97L mode run turning out too sea why 97L is saying am going W
Watch it go OTS. :D
Member Since: June 30, 2013 Posts: 12 Comments: 8187
Is there a reason the TWO was written by the Weather Prediction Center in Maryland and not by the NHC?
Member Since: Posts: Comments:
Quoting 710. nrtiwlnvragn:


I would disagree, but thats an opinion. Dry air may not be an big issue currently, but it was previous days.
Dry air was coming off the northeast coast of South America a couple of days ago.
Member Since: June 30, 2013 Posts: 12 Comments: 8187
the mode runs are doing a vary poor job with 97L mode run turning out too sea why 97L is saying am going W
Member Since: May 21, 2006 Posts: 5091 Comments: 115072
Quoting 33. CybrTeddy:
NASA isn't messing with the weather, the adverse affects by messing around with fire could do serious harm. Remember, hurricanes do serve a purpose. They cool off SSTs, bring heat to the poles, disburse heat across the Atlantic. If you take away the hurricane element something has to disburse the heat across the Atlantic, which in its own end could be even worse for people than if you'd simply allow hurricanes to go out to sea.

The answer isn't with NASA, it's simply a multi-year La Nina crossed with a continual warm AMO and -PDO. We're experiencing now what we saw in the 70s, loads of weak storms with one or two really noticeable ones. Looking at the current ENSO set-up, it's likely this will continue into next year.
?

-PDO +AMO and neutral to weak La Nina conditions are arguably the most favorable conditions you could ask for in the Atlantic. Multi-year La Ninas can become a problem, but we haven't been in a full blown multi-year La Nina. -PDO and neutral to near Nina conditions may help partially explain the global downturn in activity, but not the Atlantic's.
Member Since: Posts: Comments:
Quoting 684. Sfloridacat5:
NAM at 54 hours - 97L is on its way north to open seas. NAM has shifted further north on this run.


97L better hook right to get to that forecast point. 97L is at 63 and change west, P.R. is what? 65-67 west?
Member Since: Posts: Comments:
Quoting 707. Levi32:


Only wrong about which agency wrote the TWO. I think he's right about the actual meteorology part.


I would disagree, but thats an opinion. Dry air may not be an big issue currently, but it was previous days.
Member Since: Posts: Comments:
Member Since: June 30, 2013 Posts: 12 Comments: 8187


little better not much looks wnw towards far eastern dom as it treks up and out nnw ward into extreme se bahama region
Member Since: Posts: Comments:
Quoting 698. nrtiwlnvragn:


TWO was written by Weather Prediction Center, so as usual he is wrong.


Only wrong about which agency wrote the TWO. I think he's right about the actual meteorology part.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting 691. JLPR2:


97L looks better, there's definitely a LLC tightening up around 15N evidenced by the motion of the low level clouds.

Though in the looks department 97L is far from winning a beauty pageant.



Ha! if 97l were a beauty pageant contestant, she would rip her evening gown whilst falling down stairs, puke during her interview questions, and I don't even want to talk about the swimsuit competition.....
Member Since: Posts: Comments:
Quoting 696. HurricaneHunterJoe:


It better hurry and turn



like I said you guys you need too drop all the mode runs for 97L in tell we can get a recon fight in there with more mode run dated
Member Since: May 21, 2006 Posts: 5091 Comments: 115072
704. MahFL
97L is on the consus sat page now with quicker updates.

Member Since: Posts: Comments:
The season is so chaotic that the TV and radio mets in Puerto Rico are going crazy with 97L.
Member Since: Posts: Comments:
Area to the east of 97l is robbing it of convergence!!
Member Since: Posts: Comments:
This blog needs sustenance! 97l ain't it.
Member Since: Posts: Comments:
Quoting 680. Patrap:


At least someone gets it lol.


Some are kinda preoccupied with more distant things.
Member Since: Posts: Comments:
699. JLPR2
Quoting 695. Tropicsweatherpr:


I think is too far south at this point that it will be difficult for the low to cross PR. But plenty of rain will come anyway.


Probably, but then there is the problem that the NE side of a tropical system is usually its strongest and we should get it. :\
Member Since: Posts: Comments:
Quoting 665. IKE:
1h
NHC rightly removes dry air argument with 97L


TWO was written by Weather Prediction Center, so as usual he is wrong.
Member Since: Posts: Comments:
697. Relix
Quoting 695. Tropicsweatherpr:


I think is too far south at this point that it will be difficult for the low to cross PR. But plenty of rain will come anyway.
Its making a Beeline for Mona or Eastern RD.
Member Since: August 3, 2006 Posts: 0 Comments: 2722
Quoting 676. Sfloridacat5:
18z NAM puts 97L right on top of P.R.


It better hurry and turn
Member Since: Posts: Comments:
Quoting 691. JLPR2:


97L looks better, there's definitely a LLC tightening up around 15N evidenced by the motion of the low level clouds.

Though in the looks department 97L is far from winning a beauty pageant.



I think is too far south at this point that it will be difficult for the low to cross PR. But plenty of rain will come anyway.
Member Since: April 29, 2009 Posts: 75 Comments: 14243
Excellent read from Brad Pan's blog today about hurricane seasonal forecasts.

Link
Member Since: August 27, 2006 Posts: 0 Comments: 1760
97L will pass at least 180 miles south of PR imo.
Member Since: Posts: Comments:
LOL I like teasing you all. :)
Member Since: June 30, 2013 Posts: 12 Comments: 8187
691. JLPR2
Quoting 669. HuracandelCaribe:


97L looks better, there's definitely a LLC tightening up around 15N evidenced by the motion of the low level clouds.

Though in the looks department 97L is far from winning a beauty pageant.

Member Since: Posts: Comments:
Quoting 654. Drakoen:


He's on a 20 right now. I'm sure reality will bring him back down to a low key 6 or 7 like the rest of us.


I'm in the "hey, major hurricanes happen even in the most boring of seasons" level.
Member Since: Posts: Comments:
Quoting 660. Tazmanian:
guys tose out all the mode runs for 97L I see 97L going W


be careful Tas....you could be ostracized like WKC
Member Since: Posts: Comments:
Quoting 682. MiamiHurricanes09:
So the obvious lower-level outflow boundaries aren't a result of dry air intrusion?


I haven't seen any evidence that the actual circulation of 97L has been invaded by dry air. The outflow boundaries to the northwest I think are being caused by the accelerating trade wind flow to their west, which is pulling air down, causing convective cells to collapse. Such downdrafts can then in turn create some dry air along the northern periphery, but the point is I don't think dry air has ever really been an issue for 97L. It's been nearby, but not entrained. The inhibitor has been elongated structure and lack of the convergence necessary to sustain a CDO.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting 672. Levi32:


At least someone gets it lol.

Levi with a pos nao forming wouldn't that try to bring this slowly west from the bahamas. I am thinking the models which are based on gfs level physics are using the ne piece of energy to break a bigger weakness then there potentially will really be?
Member Since: Posts: Comments:
Everytime I see a JB re-tweet,

I tweet JB the entry here.

; )
Member Since: July 3, 2005 Posts: 423 Comments: 128228
NAM at 54 hours - 97L is on its way north to open seas. NAM has shifted further north on this run.
Member Since: Posts: Comments:
It ain't over 'til the fat lady sings. (Or 'til it's November 30th)
Member Since: Posts: Comments:
Quoting 672. Levi32:


At least someone gets it lol.
So the obvious lower-level outflow boundaries aren't a result of dry air intrusion?
Member Since: Posts: Comments:
Quoting 679. FunnelVortex:


It sucks, doesn't it?
Nope......Love it
Member Since: Posts: Comments:
Quoting 677. HurricaneHunterJoe:


Spin City


At least someone gets it lol.
Member Since: July 3, 2005 Posts: 423 Comments: 128228
Quoting 673. GTstormChaserCaleb:
The season is a bust.


It sucks, doesn't it?
Member Since: Posts: Comments:
Quoting 669. HuracandelCaribe:


I think it's moving due west.
Member Since: Posts: Comments:
Quoting 643. Patrap:


Spin City
Member Since: Posts: Comments:
18z NAM puts 97L right on top of P.R.
Member Since: Posts: Comments:
Quoting 673. GTstormChaserCaleb:
The season is a bust.
Hope so GT
Member Since: Posts: Comments:

Water Vapor of 97L.
Member Since: Posts: Comments:
The season is a bust.
Member Since: June 30, 2013 Posts: 12 Comments: 8187
Quoting 665. IKE:
1h
NHC rightly removes dry air argument with 97L


At least someone gets it lol.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Member Since: August 12, 2007 Posts: 0 Comments: 119
Quoting 660. Tazmanian:
guys tose out all the mode runs for 97L I see 97L going W

i see same thing
Member Since: Posts: Comments:
Member Since: August 12, 2007 Posts: 0 Comments: 119
Quoting 662. BVI:


Hello, which island are you on?


Hi there...over on St. Thomas in Frenchtown.

-L
Member Since: Posts: Comments:
The whole picture. And, huh, really a lot of SAL (Saharan air layer) behind it, as was pointed out by Walsh earlier. (Edit: Our Caribboy will be annoyed, for sure)



Member Since: Posts: Comments:

Viewing: 717 - 667

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Scattered Clouds
79 °F
Scattered Clouds