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Three Atlantic disturbances to watch

By: Dr. Jeff Masters, 2:40 PM GMT on October 03, 2007

A low pressure system over the southern Gulf of Mexico (90L) has developed a large surface circulation covering most of the Gulf of Mexico, but is not a threat to develop rapidly. This morning's QuikSCAT pass shows this circulation nicely, with top winds of 35 mph to the southeast of the center. Satellite loops show that 90L's heavy thunderstorm activity has decreased since yesterday. Water vapor satellite loops show a large upper-level low pressure system also covers the entire Gulf of Mexico, with two embedded swirls. This upper level low has a cold core and is wrapping plenty of dry air into 90L. These factors, plus the very large size of the surface circulation of 90L, will keep any development of the storm slow. A Hurricane Hunter aircraft is scheduled to investigate the system Thursday afternoon, if necessary. Today's flight was canceled.

The latest computer model runs continue to point to a landfall Thursday night or Friday morning near the Louisiana/Texas border. I don't see 90L becoming a hurricane, and I give equal chances of 90L arriving at the coast as a tropical disturbance, tropical depression, or tropical storm.


Figure 1. Today's line up of tropical disturbances to watch.

Disturbance 92L east of the Bahamas
Of greater concern to me is an area of heavy thunderstorm activity associated with a surface trough of low pressure (92L) that has developed just east of the Bahama Islands. This morning's QuikSCAT pass showed an east-west oriented zone of converging winds at 27N between 69W and 72W, but no surface circulation. Satellite loops show a large area of disorganized thunderstorm activity that is not getting better organized. This disturbance is under about 10-15 knots of wind shear. Wind shear is expected to remain ten knots or less over 92L for the next five days. The computer models expect 92L will move slowly west-southwest over the Bahamas, then the Florida Straits or Cuba during the next three days. By Saturday, the GFS and ECMWF models predict a tropical depression could form in the Western Caribbean or southern Gulf of Mexico. The NOGAPS and UKMET model forecast that development Monday is more likely. These are the highest heat content waters in the Atlantic, and with a upper-level anticyclone with light wind shear expected to set up over the disturbance, the potential exists for a hurricane to form from 92L next week. The Hurricane Hunters are scheduled to investigate 92L Thursday afternoon.

Disturbance 91L between Africa and the Lesser Antilles
A tropical wave (91L) near 9N, 41W, midway between Africa and the Lesser Antilles Islands, has gotten better organized this morning. This morning's QuikSCAT pass showed a wind shift associated with the wave, but no closed circulation. Satellite loops show a modest area of heavy thunderstorm activity that is not well-organized. The disturbance is headed west at 10-15 mph, and is expected to take a more west-northwesterly track Thursday.

Wind shear is about 10 knots over the wave, and is forecast to remain below 15 knots until Thursday night. This may allow for some slow development. However, beginning Thursday night, wind shear is expect to increase and remain 20-30 knots through Sunday. This should prevent further development.

I'll have an update Thursday morning at the latest.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Good morning everyone! Time to see what everyone has been writing
Ivansvrivr 1:46 PM GMT on October 04, 2007
Fidel may send 92 on down to see is pal Hugo.


lol. Not sure that far south but I agree 92L could pull a Mitch. Yukatan and Honderas have been a magnet this year
Heavy duty shear for 92L this morning.
2004. Patrap
GFDL has a end solution of 988MB..

Link
Thanks for the update Storm! Good job as usual!
I can't believe we've had this many systems in the Gulf without something major blowing up!!! Unbelievable!!!!!
Anybody who breeds bengals. They are wild and not legal in all states. Must ge 5 gens from parent leopard to be cosidered "domestic" this ones only 2/
2008. Hhunter
Interesting analysis stormw. Kinda sums up the problems challenges of trying to figure out 92L...
Winter weather report - Ice time.
The NHL Tampa Bay Lightning open their season tonight against the New Jersey [dust] Devils.

MJO 10/3/07
Good morning, StormW
"Yukatan and Honderas have been a magnet this year"

I'm leaning that way, until big Bertha Bermuda high breaks down later in season. Or until something develops and proves me wrong.
Thanks Storm
Good morning Storm. off to read Storms update, be right back
2015. Patrap
GOES WV Loop Of Atlantic,GOM 92L
Click to ENlarge
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Morn'n all.
Good analysis Storm!
2017. Patrap
QuickSCAT Pass Atlantic
12:53 UTC descending Pass

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StormW, great synopsis. Knew I could understand you, but thats because u are a Coastie, I was too for a little bit. Best station was Guam, on a bouy tender!
former ET3, USCG
CPC on Intraseasonal Oscillations: "During the summer these oscillations have a modulating effect on hurricane activity in both the Pacific and Atlantic basins."
1971. Patrap 8:30 AM CDT on October 04, 2007
mm5fsu45b 2007100400 Forecast slp Java Animation

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Can you tell how long 92L is supposed to stall out over the Yucatan?
2021. Patrap
I just link the Models...That is about all I can give ya on that...
Patrap, Is Cig smoking man up there replacing the Duracells in the quickscat?
2023. Patrap
QuickSCAT humming along on its lone transmitter. Its a tough Bird ..now way passed it design Orbital Life.A real tribute to its builders and designers. WE need another scatterometer on Orbit. Thats a given.
See that big push of dry air headed for Bahamas out of N.E on W.V.loop? That should favor development S. of Cuba too.
Agreed Patrap. The folks who made the Scat are some of the best of the best. Too bad they didn't make 2 while they were doing the project.
Ivans, the cat may be staying at 8 lbs because of the spare lives it gives up when you let it drive the Buick. lol
2030. IKE
The tropical floater on 92L has the COC near 26N, and 73W at 1011 mb's.....

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Ivansvrivr-

Yeah...I was looking at that strong ridging pushing in from the NE as well. It looks to me that the dryest air should stay just east of the Central Bahamas...I still think development could occur somewhere between there and Cuba.

See that big push of dry air headed for Bahamas out of N.E on W.V.loop? That should favor development S. of Cuba too.
2032. SamTeam
New Blog
2034. IKE
20-30 knots of shear over 92L...that'll keep it in check for awhile.
It's been raining here in SE GA most of yesterday,
all night, and now most of the morning. My german shepherd ate his dog house a while back and now he's wanting to replace it with an Ark. (I haven't found a steel dog house to replace it with yet.)
Have 90 and 92 brought any significant rainfall to the W coast of Fla yet? Someone mentioned a while back tha the fire danger was going to be high if y'all didn't get a soaker before the fall dry season kicked in.