Western Caribbean disturbance 91L remaining about the same

By: Dr. Jeff Masters , 1:47 PM GMT on October 20, 2008

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An area of disturbed weather associated with a large area of low pressure (91L) continues to fester off the coast of Belize in the Western Caribbean Sea. This morning's QuickSCAT pass revealed no surface circulation, although some rotation at higher levels of the atmosphere is apparent on satellite loops. The intensity and areal coverage of heavy thunderstorms in the disturbance increased some in the past few hours, spreading over the Cayman Islands. However pressures are not falling at present over the Western Caribbean. Wind shear is a high 20 knots.

The forecast for 91L
Wind shear is expected to remain in the 15-25 knot range over the next four days, which should allow some slow development of the disturbance. Steering currents are weak, and a slow movement west to a point near the Belize coast is possible today through Tuesday. Heavy rains will affect Belize, Mexico's eastern Yucatan Peninsula, and the Cayman Islands through Wednesday. A trough of low pressure swinging across the Midwest U.S. should be able to start pulling 91L northward or northwestward by Wednesday. Once 91L enters the Gulf of Mexico on Thursday, the trough should swing the storm to the northeast, bringing it across the west coast of Florida on Friday or Saturday. Wind shear will be very high over the Gulf of Mexico this week, in the 30-40 knot range, and I doubt 91L would be able to intensify into a hurricane in the face of that kind of shear. The 00Z (8 pm EDT) run of the GFDL model develops 91L into a tropical storm that hits Florida near Sarasota Friday morning with 50 mph winds. The 06Z (2am EDT) run of the GFS model is slower, predicting a landfall near Tampa on Saturday morning. However, this landfall may occur as a weaker subtropical storm or extratropical storm, as predicted by the latest phase space diagrams from Bob Hart at Florida State. The other reliable models do not develop 91L. NHC is giving 91L a medium (20-50% chance) of developing into a tropical depression by Wednesday, which is a reasonable forecast. It currently does not appear that 91L will interfere with the World Series baseball game scheduled to be played Thursday night in St. Petersburg, Florida. Batter up!


Figure 1. Latest satellite image of the Western Caribbean disturbance, 91L.

I'll have an update Tuesday morning.

Jeff Masters

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489. KBH
1:55 PM GMT on October 21, 2008
does anyone see that UlL pushing that large cloud mass from the north atlantic down to the islands?...could be lots more rain...
Member Since: August 28, 2008 Posts: 0 Comments: 278
488. KBH
1:51 PM GMT on October 21, 2008
good for us,. pottery, look out
Member Since: August 28, 2008 Posts: 0 Comments: 278
487. WxLogic
1:49 PM GMT on October 21, 2008
Quoting probly:
If the low level circulation redevelops under the cloud mass, isnt that a point much further north and east of where the models are generating their track from. Wouldnt that dictate a course further to the north east across sw florida?


Hmm... not quite... yes I would see a slight eastern track... but remember that it still has a High to its N that is being pushed E by a developing trough in the C CONUS, so I wouldn't think there will be much difference from the current thinking.

Now if this system does intensify enough, it could change the dynamics and well... good luck to what will happen next. lol
Member Since: August 14, 2008 Posts: 4 Comments: 4977
486. IKE
1:44 PM GMT on October 21, 2008
NEW BLOG!
Member Since: June 9, 2005 Posts: 23 Comments: 37858
485. IKE
1:42 PM GMT on October 21, 2008
NEW BLOG!
Member Since: June 9, 2005 Posts: 23 Comments: 37858
484. WxLogic
1:42 PM GMT on October 21, 2008
Hi still... I was thinking the same in regards to the motion of it. Not quite heading inland but meandering in the Gulf of Honduras (GOH), before resuming a NW motion as the weak High to its N slides E toward the W ATL region.

Let's see how things play out since tonight and tomorrow will be in my opinion decisive days as to the strengh and track of this system.
Member Since: August 14, 2008 Posts: 4 Comments: 4977
483. IKE
1:41 PM GMT on October 21, 2008
Accuweather's take on 91L.....

Development Possible in the Northwestern Caribbean

Our main concern with the Atlantic Basin is with a broad area of low pressure in place over the northwestern Caribbean. Surface observations show a broad cyclonic wind flow centered just north of the northern coast of Honduras near 17 north, 86 west. This low pressure area will not move much over the next 24 hours. A deepening upper level trough over the western United States will extend into the Gulf of Mexico by Thursday. This will force this low pressure area northward. During this process the system will move over very warm water while shear over the system diminishes for a short time. This will create a window of opportunity for development Wednesday, Wednesday night and Thursday.

During this time we expect the low pressure area to consolidate and become better organized. This could lead to the development of a tropical depression and even a storm just west over the southern Gulf of Mexico. However, computer models show increased shear developing over the eastern Gulf of Mexico Thursday night and Friday as the upper-level system moves into the eastern United States. This increased shear will prevent further development. issue will be whether this low pressure area can wrap up and strengthen quickly enough during the period of lower shear. If this development does not happen by Thursday night then it will be more difficult for this system to become an organized tropical system.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
482. probly
1:41 PM GMT on October 21, 2008
If the low level circulation redevelops under the cloud mass, isnt that a point much further north and east of where the models are generating their track from. Wouldnt that dictate a course further to the north east across sw florida?
Member Since: September 23, 2008 Posts: 0 Comments: 5
481. IKE
1:37 PM GMT on October 21, 2008
Quoting vortfix:
Latest TPC 72 hour surface forecast...valid 12Z Friday:


Photobucket



That seems about right. Maybe some decent rains for the areas that need it...hopefully not much wind.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
480. stillwaiting
1:35 PM GMT on October 21, 2008
good morning everyone!!!!,I would expect to see a ramp up w/91L as it continue's to slowly drift North or NNW and like I stated last night its center should remain over water,maybe just brushing the northeast side of the yucatan....sheer has also been slackening as I stated last night was evident on the WV....I'm still standing by my sypnosis from the last 2 days.And that is a strong TS crossing the FL peninsula between TPA and naples on friday evening....all interests in the eastern GOM should be on alert as there is still a possibilty of 91l becoming a weak cane right before landfall....
Member Since: October 5, 2007 Posts: 20 Comments: 4970
478. TheCaneWhisperer
1:32 PM GMT on October 21, 2008
Quoting mettech:
WXLOGIC

I enjoy your comments on the tropical systems. You are well versed. I worked as a Met. Tech at PBI for quite a while back in the seventies. Keep up the good wx logic!


Agree. Upper and Lower support is targeted on the area in question. One would think it will persist until one or both are lost. Surface Analysis is interesting as well.
477. WxLogic
1:30 PM GMT on October 21, 2008
Quoting mettech:
WXLOGIC

I enjoy your comments on the tropical systems. You are well versed. I worked as a Met. Tech at PBI for quite a while back in the seventies. Keep up the good wx logic!


Hehe... thx :P

I always look forward to comments from you and anybody else as there's always something you overlook that can/will change things quite a bit.
Member Since: August 14, 2008 Posts: 4 Comments: 4977
476. stormdude77
1:28 PM GMT on October 21, 2008
Quoting KBH:
Storm, you agree that those clouds are pushing south, or is that wishful thinking?


Yeah, those clouds are pushing to the south...I'm not to sure why, though. However, I'm thinking it could be due to that large ULL to the NE of the islands.
475. KBH
1:18 PM GMT on October 21, 2008
Storm, you agree that those clouds are pushing south, or is that wishful thinking?
Member Since: August 28, 2008 Posts: 0 Comments: 278
474. mettech
1:17 PM GMT on October 21, 2008
WXLOGIC

I enjoy your comments on the tropical systems. You are well versed. I worked as a Met. Tech at PBI for quite a while back in the seventies. Keep up the good wx logic!
473. stormdude77
1:13 PM GMT on October 21, 2008
472. mettech
1:13 PM GMT on October 21, 2008
CharlotteFl

I am in Port Charlotte also....You are right, the west coast of Florida is most vulnerable in October even if it's winter in north Florida.
471. WxLogic
1:13 PM GMT on October 21, 2008
Quoting mettech:
WXLOGIC

You are right, I just checked that ship report and the buoy report. Very interesting especially since the convection is becoming more enhanced.


We'll see in a couple hours as we'll need to know if that TS Cluster won't go poof!!! but the DMAX did helped it increase its TS activity along with divergence aloft.
Member Since: August 14, 2008 Posts: 4 Comments: 4977
470. charlottefl
1:06 PM GMT on October 21, 2008
73.6 here in SWFL, not too cold, not to hot, pretty much perfect. Should be interesting to see if anything comes out of the Caribbean system, getting later in the season now, but this is prime time for the W coast of FL.
Member Since: December 18, 2006 Posts: 7 Comments: 2686
469. KBH
1:02 PM GMT on October 21, 2008
Gwad, that's the same thing I been saying . Winds have now picked up from NE, so I am thinking the clouds will get pushed further south
Member Since: August 28, 2008 Posts: 0 Comments: 278
468. mettech
1:01 PM GMT on October 21, 2008
WXLOGIC

You are right, I just checked that ship report and the buoy report. Very interesting especially since the convection is becoming more enhanced.
467. IKE
1:00 PM GMT on October 21, 2008
Belize w/west winds...

Puerto Barrios, GU (Airport)
Updated: -32 sec ago
Overcast
73 °F
Overcast
Humidity: 88%
Dew Point: 70 °F
Wind: 7 mph from the West
Pressure: 29.92 in (Rising)
Visibility: 6.2 miles
UV: 0 out of 16
Clouds:
Scattered Clouds 900 ft
Overcast 8000 ft
(Above Ground Level)
Elevation: 3 ft
Member Since: June 9, 2005 Posts: 23 Comments: 37858
466. ncleclerc
12:57 PM GMT on October 21, 2008
Morning! Well, in Sanford, NC we are at 39. Had frost Monday morning and calling for more on Wednesday and Thursday. Have a blessed day!
Member Since: October 5, 2005 Posts: 0 Comments: 108
465. gwadaman
12:56 PM GMT on October 21, 2008
Morning all, still raining in Barbados, it dosen't seem to want to stop. We have probably had 2 good days of sun in 2 weeks and it looks as thou the flair up outside of Barbados will give us off & on rain & thunderstorms for the next few days.........
Member Since: July 8, 2007 Posts: 0 Comments: 147
464. KBH
12:55 PM GMT on October 21, 2008
Pottery looks like you gonna get some of these rains in bit
Member Since: August 28, 2008 Posts: 0 Comments: 278
463. conchygirl
12:54 PM GMT on October 21, 2008
Ike: Kinda/Sorta teasing. It was 68 when I came to work this morning and some folks are wearing sweaters. Not really winter weather but sure feels like the beginning of winter in central florida. And I am with Surfmom, running sure is easier in the cooer temps. NO PALOMA.
Member Since: June 11, 2008 Posts: 24 Comments: 5910
462. IKE
12:50 PM GMT on October 21, 2008
Quoting conchygirl:
Boo...We shall see. It is hard to think about storms with the winter weather slipping in. LOL


Winter weather? LOL. I know you're teasing.

It's at 56 degrees now...at my house...outside.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
461. conchygirl
12:49 PM GMT on October 21, 2008
Quoting IKE:
53 degrees with sunshine here in the Florida panhandle...

conchygirl...I sense a Paloma in the GOM...
Boo...We shall see. It is hard to think about storms with the winter weather slipping in. LOL
Member Since: June 11, 2008 Posts: 24 Comments: 5910
460. 69Viking
12:44 PM GMT on October 21, 2008
451. IKE

Hey IKE, check again I think the temp may have dropped a bit more. We just hit 49 along the coast in the Mary Esther area! What a beautiful morning, more of the same for this weekend after the front passes on Friday!
Member Since: August 25, 2006 Posts: 1 Comments: 3055
459. WxLogic
12:42 PM GMT on October 21, 2008
Quoting IKE:
91L....



A cruise liner (C6VG7) about 87NM N of Honduras has reported W winds and a pressure of 1008MB... while the Buoy 42056 to the N of the TS cluster reporting NE winds.

If this validates then there's definitely a SFC low starting to take tape further N (closer to the deep convection).
Member Since: August 14, 2008 Posts: 4 Comments: 4977
458. melwerle
12:41 PM GMT on October 21, 2008
morning Storm!
Member Since: June 28, 2006 Posts: 12 Comments: 1837
456. IKE
12:33 PM GMT on October 21, 2008
91L....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
454. Cotillion
12:27 PM GMT on October 21, 2008
Mid afternoon, and it's 10C.
About 5C this morning. Winter definitely on its way...
Member Since: August 23, 2008 Posts: 7 Comments: 5300
453. melwerle
12:20 PM GMT on October 21, 2008
Morning!

COLD here (not as cold as 6C though!). 44 degrees and sunny sunny...SO GLAD the heat finally broke.
Member Since: June 28, 2006 Posts: 12 Comments: 1837
452. KBH
12:18 PM GMT on October 21, 2008
it is dark indeed, can't see the keyboard well, gotta get the lights. Rains now starting here and winds have picked up too..
Member Since: August 28, 2008 Posts: 0 Comments: 278
451. IKE
12:16 PM GMT on October 21, 2008
53 degrees with sunshine here in the Florida panhandle...

conchygirl...I sense a Paloma in the GOM...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
450. TheCaneWhisperer
12:14 PM GMT on October 21, 2008
Morning All.

68 degrees in Jupiter, FL this morning. Absolutely beautiful. I've been waiting for this all year.

Pretty broad area of low pressure and convergence associated with 91L. Once steering currents pick up a bit, the speculated center relocation could happen. Ya have to think, being there so darned long, something will eventually come of it. Law of averages.
449. conchygirl
12:14 PM GMT on October 21, 2008
Quoting conchygirl:
Try this again, last post I said - Hi and loving the cooler weather.
Member Since: June 11, 2008 Posts: 24 Comments: 5910
448. conchygirl
12:13 PM GMT on October 21, 2008
Quoting WxLogic:
Hi... Conchy...
Member Since: June 11, 2008 Posts: 24 Comments: 5910
447. stormdude77
12:09 PM GMT on October 21, 2008
See ya pottery!
446. WxLogic
12:08 PM GMT on October 21, 2008
Hi... Conchy...
Member Since: August 14, 2008 Posts: 4 Comments: 4977
445. pottery
12:07 PM GMT on October 21, 2008
Sounds good, Conchy.
I am out .......
Member Since: October 24, 2005 Posts: 0 Comments: 24390
444. conchygirl
12:04 PM GMT on October 21, 2008
Morning all: Gorgeous morning here...cool with light drizzle. Really believe H season is over.
Member Since: June 11, 2008 Posts: 24 Comments: 5910
443. pottery
12:03 PM GMT on October 21, 2008
Interesting fact-
lightening "fixes" nitrogen in the air, which falls as fertilizer. Its good for your vegetation.
Member Since: October 24, 2005 Posts: 0 Comments: 24390
442. stormdude77
12:02 PM GMT on October 21, 2008
It's now starting to rain here...it's looking very ominous outside...
441. pottery
12:01 PM GMT on October 21, 2008
Lightening that close, when you hear the zzzzzzz and bang, is energizing.!!
Member Since: October 24, 2005 Posts: 0 Comments: 24390
440. KBH
11:57 AM GMT on October 21, 2008
Quoting stormdude77:


Wow...

car alwrms were going off like crazy, it was close enough that I heard that zzzz then the loud bang!
Member Since: August 28, 2008 Posts: 0 Comments: 278
439. pottery
11:56 AM GMT on October 21, 2008
KBH, deffinitely December-ish. 24c here at 4 am. Thats low for October......
Member Since: October 24, 2005 Posts: 0 Comments: 24390

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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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