Invest 94L and the Lesser Antilles

By: Dr. Jeff Masters , 9:51 AM GMT on August 30, 2009

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Hi, this is Dr. Rob Carver filling in for Dr. Masters. The convection associated with Invest 94L has intensified, prompting the NHC to issue an early Tropical Weather Outlook to update the situation. Essentially, people in the Lesser Antilles need to start paying attention to the seas and skies. Looking at the computer track models, the set of model solutions are fairly similar to the Saturday model runs. A set of dynamical models (GFDL, HWRF, NOGAPS) runs to the NE of the Antilles, while the simpler models (LBAR, BAM family) are more easterly and take 94L over the Antilles. I do not ascribe any significance to the 00Z GFS track following the simpler models over the dynamical models. From my examination of the 00Z GFS run, it looks like the simulated 94L weakens too much, so the automatic vortex tracker picks up another vorticity feature. As for the future of 94L, there is a large area of large wind shear to it's north. It will need to keep it's track at WNW-W for intensification.

Update at 6AM EDT
I would be remiss if I didn't mention the major hurricane in the Eastern Pacific, Jimena At this time, Jimena has a satellite-estimated maximum wind speed of 115 mph, making it a Category 3 storm on the Saffir-Simpson scale. Jimena has an impressive presentation in satellite imagery with a large area of cold anvil cirrus in the center of the storm. The following microwave imagery indicate the formation of a relatively potent central eyewall, which is responsible for intensification.


Fig. 1 SSMI 85 GHz PCT at 0244Z Aug 30. Image courtesy of NRL.


People along the western coast of Mexico and along along the Baja need to pay close attention to this dangerous storm. I emphasize that using the current track and intensity forecast, Jimena will be a Category 4 storm when it approaches the tip of Baja and a Category 3 storm when it makes landfall up the coast.

It is worth noting that if Jimena follows the more easterly tracks presented in the computer track forecasts, the remnants of Jimena could impact NM and western Texas.


I'll update this entry further in response to 94L's development.


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Quoting NewYork4Life:


I credit my 2 years of majoring in Meteorology...:)
Congrats! I hope your right.
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Wow. Interesting shift in the GFS.
Member Since: October 25, 2005 Posts: 19 Comments: 22323
1306. Seastep
jacksbeachbum - also, steering is completely separate from shear. Look at them independently.
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Quoting TexasHurricane:


SHIPS takes it to 103 mph at 120 hrs....interesting
Member Since: June 29, 2009 Posts: 13 Comments: 5313
Quoting stormsurge39:
Very observant! Or it could be a hurricane!


I credit my 2 years of majoring in Meteorology...:)
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
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futuremet was relatively agnostic on 94L today.

Haven't seen StormW in the blog for a while.
Member Since: October 25, 2005 Posts: 19 Comments: 22323
Banding is on the increase with 94L. Circulation appears to be tightening up a bit on visible as well.
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Quoting NewYork4Life:
94L might very well develop into absolutely nothing...
Very observant! Or it could be a hurricane!
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1297. Seastep
Quoting jaxbeachbum:
Is 94L being steered by upper level winds or mid-level winds? Maybe both? If I'm looking at the shear maps correctly, shear is a lot lower in the mid-levels.


Steering
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94L might very well develop into absolutely nothing...
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Quoting nrtiwlnvragn:


Disturbance

Format Guide


That format guide is great. Thank you for posting that link.
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Anyone know what StormW or Futuremet think of the 94l? Any new thoughts as to what it may do or where it may go? By the models it looks like it shifted more to the west instead of the more north route they had before.
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Funny when Claudette was in the GOM, never found any faults with her. Actually was leaning towards her.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
HPC has 94L ~25N ~72W in 7 days Link
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Is 94L being steered by upper level winds or mid-level winds? Maybe both? If I'm looking at the shear maps correctly, shear is a lot lower in the mid-levels.
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1289. Gorty
Looks like it is starting to look less elongated, slowly but surly. I'd say a T.D. somtime tonight and a T.S. sometime Monday.
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Quoting Grothar:


You are not alone, my friend. Even after I read them I still don't understand them. Ever notice why I ask so many questions and provide so little in the way of opinion. I leave that to the ones on here who do.
Exactly!
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Quoting KBH:
if this wind shear from the SE does not materialise will the sytem continue to move W or NW?


I'm not 100% sure, but I don't believe that wind shear as any affect on the direction in which a storm moves.
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30/1745 UTC 11.9N 47.5W T1.5/1.5 94L
30/1145 UTC 11.9N 46.1W T1.5/1.5 94L
30/0345 UTC 10.7N 45.2W T1.0/1.0 94L
29/2345 UTC 10.3N 44.8W T1.0/1.0 94L
29/1745 UTC 10.3N 44.1W T1.0/1.0 94L
29/1145 UTC 9.8N 42.4W TOO WEAK 94L
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1285. hydrus
Quoting Grothar:


My mother, who is now deceased lived in Rio Vista in 1940's, remembered the 1947 one well. There was also a gigantic rain-maker the following year in the same area.
There were 2 hurricanes that effected S. FL in both 47, and 48,in which they had huge flooding issues for months in both years.
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1284. Grothar
Quoting stormsurge39:
Thanks everybody for answering questions in here. I can read and understand easy things, but its hard to me to understand steering maps and wind sheer.


You are not alone, my friend. Even after I read them I still don't understand them. Ever notice why I ask so many questions and provide so little in the way of opinion. I leave that to the ones on here who do.
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Quoting KEEPEROFTHEGATE:
WTNT01 KNGU 301201
SUBJ/TROPICAL CYCLONE FORMATION ALERT 301200Z AUG 09//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 12.1N 45.2W TO 15.1N 51.5W
WITHIN 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. THE SYSTEM
IS MOVING NORTHWESTWARD AT 15 KNOTS.
2. REMARKS: THE 09Z SATELLITE IMAGERY INDICATES THAT THE DEEP
CONVECTION AND A SURFACE CIRCULATION ASSOCIATED WITH THE LOW HAS
BECOME BETTER ORGANIZED OVER THE PAST 12 HOURS. SEA SURFACE
TEMPERATURES ARE RANGING FROM 28 TO 30 DEGREES CELSIUS ACROSS THE
TROPICAL ATLANTIC. UPPER LEVEL WINDS OVER THE SYSTEM ARE EAST-
SOUTHEASTERLY 25 TO 30 KTS. WINDS, HOWEVER, ARE DECREASING WEST
OF THE WAVE. AS THE WAVE CONTINUES TO TRACK TO THE WEST,
ENVIRONMENTAL CONDITIONS BECOME MORE CONDUCIVE FOR DEVELOPMENT.
3. THIS ALERT IS VALID THROUGH 311200Z.//
NOW NW!! Your right 456 its pick and choose right now.
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1280. KBH
if this wind shear from the SE does not materialise will the sytem continue to move W or NW?
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img src="H" alt="" />

Cat 5 ?!
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I'll highlight everything since its correct thing to do. Why highlight elongated when the TPC also said well define.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...SPECIAL FEATURE...

TROPICAL WAVE EXTENDS FROM 9N47W TO 17N45W WITH AN ASSOCIATED
1007 MB LOW PRESSURE CENTER NEAR 11N46W. THE WAVE WAS MOVING
WEST AT 15 KT AS AVERAGED OVER THE PAST 24 HOURS.
VISIBLE
SATELLITE IMAGERY INDICATED A WELL DEFINED CIRCULATION WHICH
STILL APPEARED TO BE ELONGATED ALONG A SSW TO NNE AXIS.
BUOY
41041 REPORTED A SHARP WIND SHIFT FROM NE TO SSE AT 1300 UTC
WHICH SUPPORTED THE EXTENSION OF THE WAVE AXIS NORTHWARD.
SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS CONFINED
TO THE W SEMICIRCLE OF THE LOW AND WEST OF THE WAVE AXIS WITHIN
60 NM OF A LINE THROUGH 10N49W-13N49W-15N47W-17N45W.
ADDITIONAL
SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED WITHIN THE
AREA FROM 08N TO 12N BETWEEN 50W AND 55W. THE CHANCE FOR THIS
SYSTEM TO BECOME A TROPICAL CYCLONE DURING THE NEXT 48 HOURS HAS
BEEN ELEVATED TO HIGH.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1277. IKE
Quoting stormsurge39:
Is it WNW or W? That is confusing!


I see the center between 12-13 N and 47-48 W, moving WNW.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1276. KEEPEROFTHEGATE (Mod)
WTNT01 KNGU 301201
SUBJ/TROPICAL CYCLONE FORMATION ALERT 30 AUG 09//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 12.1N 45.2W TO 15.1N 51.5W
WITHIN 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. THE SYSTEM
IS MOVING NORTHWESTWARD AT 15 KNOTS.
2. REMARKS: THE 09Z SATELLITE IMAGERY INDICATES THAT THE DEEP
CONVECTION AND A SURFACE CIRCULATION ASSOCIATED WITH THE LOW HAS
BECOME BETTER ORGANIZED OVER THE PAST 12 HOURS. SEA SURFACE
TEMPERATURES ARE RANGING FROM 28 TO 30 DEGREES CELSIUS ACROSS THE
TROPICAL ATLANTIC. UPPER LEVEL WINDS OVER THE SYSTEM ARE EAST-
SOUTHEASTERLY 25 TO 30 KTS. WINDS, HOWEVER, ARE DECREASING WEST
OF THE WAVE. AS THE WAVE CONTINUES TO TRACK TO THE WEST,
ENVIRONMENTAL CONDITIONS BECOME MORE CONDUCIVE FOR DEVELOPMENT.
3. THIS ALERT IS VALID THROUGH 311200Z.//
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1274. Grothar
Quoting BahaHurican:
BTW, the 1947 hurricane is the "famous" Fort Lauderdale / Pompano hurricane.



My mother, who is now deceased lived in Rio Vista in 1940's, remembered the 1947 one well. There was also a gigantic rain-maker the following year in the same area.
Member Since: Posts: Comments:
1273. Seastep
Quoting IKE:
BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...SPECIAL FEATURE...

TROPICAL WAVE EXTENDS FROM 9N47W TO 17N45W WITH AN ASSOCIATED
1007 MB LOW PRESSURE CENTER NEAR 11N46W. THE WAVE WAS MOVING
WEST AT 15 KT AS AVERAGED OVER THE PAST 24 HOURS. VISIBLE
SATELLITE IMAGERY INDICATED A WELL DEFINED CIRCULATION WHICH
STILL APPEARED TO BE ELONGATED ALONG A SSW TO NNE AXIS.

I looked up the definition of what the NHC says about 94L...as elongated.

From wordweb..."Make long or longer by pulling and stretching."


imo, not going to be elongated for much longer.
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Quoting Tazmanian:



what dos DB mean???


Disturbance

Format Guide
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Quoting stormsurge39:
Is it WNW or W? That is confusing!


its call pick and choose.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting IKE:
BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...SPECIAL FEATURE...

TROPICAL WAVE EXTENDS FROM 9N47W TO 17N45W WITH AN ASSOCIATED
1007 MB LOW PRESSURE CENTER NEAR 11N46W. THE WAVE WAS MOVING
WEST AT 15 KT AS AVERAGED OVER THE PAST 24 HOURS. VISIBLE
SATELLITE IMAGERY INDICATED A WELL DEFINED CIRCULATION WHICH
STILL APPEARED TO BE ELONGATED ALONG A SSW TO NNE AXIS.

I looked up the definition of what the NHC says about 94L...as elongated.

From wordweb..."Make long or longer by pulling and stretching."
Is it WNW or W? That is confusing!
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Quoting CosmicEvents:

Agreed. You and I see the same thing, Dr.
I don't know what the other doctors are looking at.


its call pick and choose
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1267. KEEPEROFTHEGATE (Mod)


T.C.F.A.
INV/94/XXL
MARK
12.1N/47.5N
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DISTURBANCE INVEST (AL942009) 20090830 1800 UTC

...INITIAL CONDITIONS...
LATCUR = 12.1N LONCUR = 47.5W DIRCUR = 290DEG SPDCUR = 12KT
LATM12 = 11.2N LONM12 = 45.1W DIRM12 = 290DEG SPDM12 = 15KT
LATM24 = 10.6N LONM24 = 42.0W
WNDCUR = 25KT RMAXWD = 60NM WNDM12 = 25KT
CENPRS = 1007MB OUTPRS = 1011MB OUTRAD = 150NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

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.3 degrees north while moving 1.2 degrees west.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1264. Seastep
lol. too late.
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1263. Parkay
Quoting Hhunter:


purple spot i see possible swirl...


Looks like the GFS develops it into sort of something that comes ashore in mexico then gets shoved north and east back into texas.

Hmm. Combine that with the hurricane off the pacific coast of mexico, someone's in for a soaking.
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1262. IKE
BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...SPECIAL FEATURE...

TROPICAL WAVE EXTENDS FROM 9N47W TO 17N45W WITH AN ASSOCIATED
1007 MB LOW PRESSURE CENTER NEAR 11N46W. THE WAVE WAS MOVING
WEST AT 15 KT AS AVERAGED OVER THE PAST 24 HOURS. VISIBLE
SATELLITE IMAGERY INDICATED A WELL DEFINED CIRCULATION WHICH
STILL APPEARED TO BE ELONGATED ALONG A SSW TO NNE AXIS.

I looked up the definition of what the NHC says about 94L...as elongated.

From wordweb..."Make long or longer by pulling and stretching."
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1261. Seastep
I have 12N/47.5W based on rgb and this.
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It's possible that I missed it, but for all the people who are saying that 94L will become a TD at 5, is there any evidence such as a QuikScat that shows a closed circulation?
I'm just wondering. Thanks.
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1259. KBH
Quoting Stormchaser2007:


Correct...they show direction.

Well the forecast for B'dos seems to suggest that will not happen till Tuesday/Wednesday, which tells me that 94L will be in our area before then

Wind forecast for B'dos
Sunday Wind ENE 28 km/h
Sunday Night Wind ENE 32 km/h .

Monday East 28 km/h .
Monday Night Wind ENE 21 km/h .
Tuesday Wind East 18 km/h
Tuesday Night SE 18 km/h
Wednesday Wind SE 14 km/h . Heat index: 40 °C
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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.