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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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: October 25, 2008 Posts: 50 Comments: 5563
Bottom continues to fall

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665. IKE
1h
NHC rightly removes dry air argument with 97L
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Member Since: July 3, 2005 Posts: 419 Comments: 127377
I see 97L went up 10%.

Getting its act together.
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662. BVI
Quoting 661. VirginIslandsVisitor:
Well, my towel brigade is already being brought into force. Just had another line go through. Rain was falling sideways. Lots of water coming in from under the door and plants got knocked off the porch with the wind. Now it's calm again. I'm starting to think it's going to be an interesting couple of days around here.

Lindy


Hello, which island are you on?
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Well, my towel brigade is already being brought into force. Just had another line go through. Rain was falling sideways. Lots of water coming in from under the door and plants got knocked off the porch with the wind. Now it's calm again. I'm starting to think it's going to be an interesting couple of days around here.

Lindy
Member Since: July 30, 2011 Posts: 1 Comments: 583
guys tose out all the mode runs for 97L I see 97L going W
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Quoting 652. CybrTeddy:


The ECMWF hardly developed 96L. Makes it a strengthening tropical storm by the end of the run.


How the models did with 98L?
Member Since: April 29, 2009 Posts: 75 Comments: 13931
There is a growing risk of a significant tropical cyclone impacting the se conus by mid part of next week.
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6 hourly soundings from the midwest/northeast/ and southeast will be needed by thursday to help resolve the pattern which is tricky.
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656. Relix
97L is really getting that engine revving up.
Member Since: August 3, 2006 Posts: 0 Comments: 2642
It's pretty neat to be able to scale the NASA Global Hawk track image the same as the 97L floater visible satellite image, click back and forth between the two, and see what part of the system the aircraft is in at the moment, in real time.
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Quoting 646. TropicalAnalystwx13:

Whoa, calm down there. This is 2013 we're talking about.


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.
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Member Since: July 3, 2005 Posts: 419 Comments: 127377
Quoting 649. MiamiHurricanes09:
I agree. Even though models have the system emerging within 5 days as a tropical storm...all the exact same models had 96L emerging Africa within 5 days as a tropical storm and all we got was a puff of clouds.


The ECMWF hardly developed 96L. Makes it a strengthening tropical storm by the end of the run.
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Quoting 646. TropicalAnalystwx13:

Whoa, calm down there. This is 2013 we're talking about.


Like X 1000

Now your coming around
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Quoting 643. Patrap:

Nice swirl over Cancun
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Quoting 646. TropicalAnalystwx13:

Whoa, calm down there. This is 2013 we're talking about.
I agree. Even though models have the system emerging within 5 days as a tropical storm...all the exact same models had 96L emerging Africa within 5 days as a tropical storm and all we got was a puff of clouds.
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Member Since: July 3, 2005 Posts: 419 Comments: 127377
For everyone thinking 97L is going out to sea then think again as the Euro is hell bent on sending 97L to FL as a weak system. Also the GFS ensembles are trending more and more on a bend west back toward FL. Something to watch down the road.

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Quoting 630. CybrTeddy:


More than likely will be our first hurricane, perhaps even major hurricane. Probably the most enthusiastic the ECMWF has been about development in the Atlantic in a year.

Whoa, calm down there. This is 2013 we're talking about.
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It's like there's an invisible barrier protecting the CONUS....
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Quoting 642. barbamz:


Human hurricane hunter would have done it more tidily than this erraticly flying drone, lol.


Well, A Air Force Captain is flying it from Virginia, sooooooooooo
Member Since: July 3, 2005 Posts: 419 Comments: 127377
Member Since: July 3, 2005 Posts: 419 Comments: 127377

Screenshot. Source.

Human hurricane hunters would have done it more tidily than this erraticly flying drone, lol.
Member Since: October 25, 2008 Posts: 50 Comments: 5563
Quoting 614. weathermanwannabe:
Here is the closet bouy to the action around 97L:

Station 42060
NDBC
Location: 16.332N 63.24W
Date: Tue, 3 Sep 2013 18:50:00 UTC

Winds: E (80°) at 21.4 kt gusting to 25.3 kt
Significant Wave Height: 5.9 ft
Dominant Wave Period: 6 sec
Mean Wave Direction: ENE (71°)
Atmospheric Pressure: 29.79 in and falling
Air Temperature: 81.1 F
Dew Point: 76.1 F
Water Temperature: 84.2 F



Pressures are lowering and banding occuring on the southern end of the system. This could imply some organization might try to take place tonight and tomorrow starting to see some. You can see the old vort by 14N/63W being sucked into the stronger one further north around 15.2N/63.1W

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Quoting 635. Drakoen:
Still seeing those outflow boundaries off to the northwest associated with dry, upper level convergent conditions.
Great way to read my mind. :P
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Quoting 629. Hurricanes305:
97L finally getting its vort together its movement into the Caribbean as allowed for it be meet up the the extra vort that extended to the northern SA coast.



Now that it has improved the area to its east is its only vort it need a little more work on. Its lacks a dominant LLC but it has tighten up significantly today and some steady organization is possible through tomorrow.



Yay! it's finally moving!!!
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Although the inner core structure of 97L continues to improve, the lack of moisture within the mid-levels of the atmosphere will force shower and thunderstorm activity to remain scarce.

97L is heading into an area of converging winds aloft which will only help keep the convective activity meager.

The 30% chance the NHC/CPC is giving 97L for development over the next 2 days seems spot on to me.
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Afternoon all.
Quoting 603. Drakoen:


Surface observations continue to indicate things trying to come to together. Whether or not it will completely is anyone's guess.
This I am observing. With the swing towards the NW in the track seen over the last 48, I am watching very closely indeed.

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What's this, what's this?!! I see?
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Still seeing those outflow boundaries off to the northwest associated with dry, upper level convergent conditions.
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StormTrackerScott good call, this cell just blew up right over us, looking outside the window from the 2nd story in my room shows the parking lots flooded.

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the moisture to the east is moving ne so it will be affected first by the tutt coming down in a few days
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Quoting 607. barbamz:


This sentence is too short for me (as a German) to figure out what you're meaning, lol. Several translations possible.


on water vapor it is rolling like a wheel again...it had stopped yesterday.
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631. TXCWC
Bermuda needs to keep an eye on 97L

GFS


GEM


NAVGEM


UKMET


FIM-9


NAEFS
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Quoting 621. TXCWC:
Most major models still showing Cape Verde system by late this weekend.

EURO


GFS


GEM


FIM-9


NAEFS (GEM+GFS ensemble mean)


More than likely will be our first hurricane, perhaps even major hurricane. Probably the most enthusiastic the ECMWF has been about development in the Atlantic in a year.
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97L finally getting its vort together its movement into the Caribbean as allowed for it be meet up the the extra vort that extended to the northern SA coast.



Now that it has improved the area to its east is its only vort it need a little more work on. Its lacks a dominant LLC but it has tighten up significantly today and some steady organization is possible through tomorrow.


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This season is boring and one of the least active we have ever had on record



yeah...a broken record...ta da da boom.....least active?.....
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Quoting GTstormChaserCaleb:
Surprised no one is posting satellite imagery of 97L. :P

I think that this system is evolving quite nicely this afternoon as it move WNW ...
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The Trough over the east coast is gonna curve out anything that comes close to the US... This season is boring and one of the least active we have ever had on record.
*Yawn* is it winter yet?
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Gonna head out for the afternoon but just noting that you can see that big ULL/Tutt cell spinning on the WV loop below centered just to the SE of Jamaica. That will cause problems for 97L as it approaches in a few days as well as help steer it towards the NW over Hispanola.

Link

My point is that 97L has a small window of opportunity over the next 48 hours to get a groove on before the encounter. Nonetheless, PR is in the bulls eye for the flooding rains at the moment.

Check back with Yall in the am to see how it does overnight................WW.

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Hmmmmmmmmmmm.........


Computer Glitch Causes False Weather Emergency Alert

August 28, 2013

An emergency weather alert was set off in all buildings at 1:42 p.m. Wednesday afternoon stating that all classes were cancelled for the rest of the day.

Three minutes later, an email was sent to all students from SRU Communication that the alert was an accident and that classes will meet as scheduled.

“It came out of our office,” stated Slippery Rock University Officer Karl Fisher. “It was not an emergency alert, but an accidental trip.”

“It was a glitch in the system,” he continued. “It sent out the alert and then locked up so there was nothing we could do until just minute ago to tell everybody that it wasn’t real.”
 
- See more at: http://www.theonlinerocket.com/news/2013/08/28/com puter-glitch-causes-false-weather-emergency-alert/ #sthash.Wr5Hfbtg.dpuf
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Could 97L be another Hortense for PR?
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Big envelope for 97L.
Member Since: October 25, 2008 Posts: 50 Comments: 5563
621. TXCWC
Most major models still showing Cape Verde system by late this weekend.

EURO


GFS


GEM


FIM-9


NAEFS (GEM+GFS ensemble mean)
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The First AF RECON Teal Flight is tomorrow after today's flight crew and ferry crew rest.

Plan of the Day


000
NOUS42 KNHC 031442
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1040 AM EDT TUE 03 SEPTEMBER 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 04/1100Z TO 05/1100Z SEPTEMBER 2013
TCPOD NUMBER.....13-094

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (CARIBBEAN)
FLIGHT ONE -- TEAL 70
A. 04/1800Z
B. AFXXX 01DDA INVEST
C. 04/1700Z
D. 16.8N 65.5W
E. 04/1730Z TO 04/2130Z
F. SFC TO 10,000 FT
Member Since: July 3, 2005 Posts: 419 Comments: 127377
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1125 AM EDT TUE SEP 03 2013

VALID 12Z FRI SEP 06 2013 - 12Z TUE SEP 10 2013


THE 00Z/03 EUROPEAN CENTRE GUIDANCE--BOTH THE DETERMINISTIC MODEL
AND THE ENSEMBLE MEAN--WERE OUT OF TOLERANCE ENOUGH WITH THE REST
OF THE GLOBAL NUMERICAL SOLUTIONS TO PRECLUDE INCLUSION IN THE
MANUAL BLEND FOR THIS FORECAST. THE CRITICAL DIVERGENCE IS WITH
REGARD TO THE SECOND BATCH OF CONTINENTAL POLAR AIR SLATED TO
CROSS SOUTHEASTERN CANADA DAYS 5 THROUGH 7. THE 00Z/03 EC GUIDANCE
IS MUCH LESS AMPLIFIED WITH THIS WAVE THAN THE RECENT GFS RUNS,
GEFS MEANS, AND CMCE MEANS.
FURTHERMORE, THE 00Z/03 ECMWF BROKE
CONTINUITY WITH ITS PREVIOUS RUNS IN THIS REGARD, AND THE LAST
FOUR ECENS MEANS HAVE BEEN UNUSUALLY UNSTABLE. SUCH INSTABILITY IN
RELIABLE GUIDANCE SUCH AS THE ECENS MEAN LIKELY SIGNALS A
DECEPTIVELY COMPLEX FLOW COMING DOWN THE PIPE,
BUT IF PERSISTENCE
COUNTS FOR ANYTHING--AS IT HAS THIS MOST RECENT SUMMER--THEN
ANOTHER COOL HIGH IS THE LIKELIEST OUTCOME FOR THE NORTHEAST DAYS
6 AND 7.

THE EAST LOOKS DRY, WITH MOST OF THE PRECIPITATION THIS PERIOD IN
ASSOCIATION WITH THE HEIGHT FALLS ACROSS THE NORTHERN ROCKIES AND
NORTHERN GREAT PLAINS. THE SOUTHWEST MONSOON--WHILE NOT QUITE IN
ITS "DEATH THROES"--CERTAINLY SEEMS TO BE ON THE WANE. EASTERLY
FLOW INTO SOUTH TEXAS SHOULD KEEP THAT REGION SHOWERY.
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Wind speed probability of 50 knots take note of the track as well.

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Quoting Kyon5:

Is it going to investigate this system this evening?
They should, the COC will be about 30 t0 40 miles SE of St. Croix, heading to the SW of Puerto Rico and the Mona canal. ,not to far, from were the plane had landed.
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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.