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Not much change to the three Atlantic disturbances

By: Dr. Jeff Masters, 2:02 PM GMT on October 04, 2007

A low pressure system over the southern Gulf of Mexico (90L) continues to be unimpressive. This morning's QuikSCAT pass shows this circulation nicely, with top winds of 30 mph south of the Louisiana coast. Satellite loops show only a small amount of heavy thunderstorm activity, to the northeast of the center. This activity is now visible on New Orleans long range radar. Water vapor satellite loops show a large upper-level low pressure system also covers the entire Gulf of Mexico, with 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. With 90L expected to make landfall Friday near the Texas/Lousiana border, I don't expect 90L will become a tropical storm. However, I do expect it will develop enough heavy thunderstorm activity today to potentially become a tropical depression and cause some isolated flooding problems in southern Louisiana tonight through Friday afternoon. The Hurricane Hunter aircraft scheduled to investigate 90L this afternoon was canceled, and has been rescheduled for Friday afternoon.


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

Disturbance 92L northeast of the Bahamas
Of greater concern is an area of heavy thunderstorm activity associated with a surface trough of low pressure (92L) near 26N 73W, just northeast of the Bahama Islands. Last night's QuikSCAT pass showed a 200-mile long southeast-northwest oriented zone of converging winds just northeast of the Bahamas, 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 15-30 knots of wind shear, and development today will be very slow. Wind shear is expected to fall to 10-15 knots beginning Friday afternoon, which may allow 92L to develop into a tropical depression as early as Saturday. The computer models expect a strong ridge of high pressure will force 92L slowly west-southwest over the Bahamas Friday and Saturday, then over the Florida Keys and western Cuba Saturday and Sunday. The storm will probably bring heavy rains to the western Bahamas, South Florida, and the Florida Keys beginning on Saturday. By Monday and Tuesday, the system is expected to be over the Western Caribbean or southern Gulf of Mexico near the Yucatan Peninsula. The GFDL and SHIPS models predict 92L will be a strong tropical storm with 55-65 mph winds on Tuesday. With an upper-level anticyclone with light wind shear expected to set up over the disturbance, the potential exists for a hurricane to form--if 92L can avoid the Yucatan.

The long term fate of the storm is highly uncertain. The GFS model predicts the ridge of high pressure ridge forcing it west will intensify, pushing 92L southwestward into Mexico. There is, however, a strong trough of low pressure expected to swing across the central U.S. next week and become a cut-off low. This system may be able to swing 92L northwards into the U.S. Gulf Coast, as the Canadian model is predicting. The Hurricane Hunters were scheduled to investigate 92L this afternoon, but this flight was canceled and has been rescheduled for Friday afternoon.

Disturbance 91L between Africa and the Lesser Antilles
A tropical wave (91L) near 10N, 45W, midway between Africa and the Lesser Antilles Islands, has become less organized since yesterday. Satellite loops show scattered disorganized heavy thunderstorm activity. The disturbance is headed west-northwest at 10-15 mph.

Wind shear is about 15 knots over the wave, which may allow for some slow development today. However, beginning tonight, wind shear is expect to increase to 20 knots, and will remain 20-35 knots through Monday. This should prevent further development. None of the computer models develop 91L.

Typhoon Krosa takes aim at Taiwan
After a slower than usual September, things have heated up in the Western Pacific this week. Typhoon Krosa, a Category 4 storm with 135 mph winds, is forecast to pass close to the northern tip of Taiwan Saturday, then brush the coast of Mainland China near Shanghai early next week.

I'll have an update Friday 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

... do we have falling pressures near the keys this morning???

If so... we may have something forming today SOUTH of FLorida possibly moving into the Gulf...

look at the visible and radar out of Miami...
I checked... the pressure has actually RISEN near the keys this morning...
THE CARIBBEAN SEA...
UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS THE AREA AS A RESULT
OF THE DEVELOPING 24N68W MIDDLE TO UPPER LEVEL ATLANTIC CYCLONIC
CIRCULATION CENTER. THIS CYCLONIC CENTER IS DIGGING SOUTHWESTWARD
SENDING THE UPPER LEVEL ANTICYCLONIC OUTFLOW SOUTHWARD INTO THE
CARIBBEAN SEA. THE ANTICYCLONIC FLOW IN THE CARIBBEAN SEA WEST
OF 70W IS DUE TO AN ALREADY-EXISTING ANTICYCLONIC CIRCULATION
CENTER NEAR 20N80W. THIS IS THE ANTICYCLONIC FLOW THAT HAD SPENT
AT LEAST THE LAST FEW DAYS COVERING THE ATLANTIC OCEAN FROM 20N
TO 30N BETWEEN 60W AND 80W. STRONG SHOWERS AND THUNDERSTORMS ARE
FROM 13N TO 16N BETWEEN 75W AND 77W. ISOLATED TO WIDELY SCATTERED
MODERATE SHOWERS AND SOME THUNDERSTORMS FROM FROM 16N TO 20N
BETWEEN 79W AND 84W. A SURFACE TROUGH EXTENDS IS ALONG 81W/82W
FROM 17N TO 21N. A 1010 MB LOW PRESSURE CENTER IS FORECAST TO
DEVELOP IN THE NORTHWESTERN CORNER OF THE AREA OR ON TOP OF
WESTERN CUBA DURING THE NEXT 24 HOURS.

Are there any fronts forecast to swing down anytime soon?
1506. IKE
6Z NAM shows a low developing in the NW Caribbean and heading west....shows the low north of PR getting drawn north..then NE by a trough coming down in 84 hours.....

Link
At the end of the day, I think these will be classified as separate systems, IMO. Givin that the system north of PR develops into anything more than a Mid-Upper Low.
1508. icmoore
Didn't Storm mention a low developing soon in the Caribbean? Cat
THE SURFACE LOW
NW OF ANDROS ISLAND APPEARS TO BE ONE OF MANY LOW LEVEL VORTICES
EXPECTED TO DEVELOP AS IMPULSES ROTATE ABOUT THE HIGH PRES AND ALONG
THE TROUGH. ALL MODELS HAVE INITIALIZED MAIN SURFACE LOW PRES TO
DEVELOP E OF THE CENTRAL BAHAMAS...MOVING THE SYSTEM SW THROUGH THE
LOWER FLA STRAITS INTO YUCATAN CHANNEL BY SUN.

The swirl in the Florida Straights is the one referenced as NW of Andros. Discussion from 3:30 am this morning.

Link
1510. nash28
The 00z run of the ECMWF shows a developing Low that moves NNE in the BOC, but that is over 200hrs out. Nothing to worry about right now.
sorry Taz... I didn't realize it would be a problem, I modified it and will only post "stills" and links from now on.
Link

90L's last attempt at a blowup....aint gunna make it though
1513. 0741
JP you were right about low or ull north PR but nhc have not pick it up yet if dont that mean it not thing worry about
90L also seems to be moving more NW'erly, at least for the moment.
Today, Typhoon "INENG" (Super Typhoon Krosa)was located based on satellite and surface data at 310 kms east northeast of Basco, Batanes (21.1°N, 125.0°E) with maximum winds of 185 kph near the center and gustiness of up to 220 kph. It is forecast to move northwest at 15 kph. Looking at the predicted path Super Typhoon Krosa will hit Taipei square on. Only chance of a downgrade is the high mountains on the southern coastline which Super Typhoon Krosa has to go, over to have a direct hit on Taipei. Cheers AussieStorm

P.S hope my images aren't to big, first time I have posted an image.

Moderate Upper Level Northwesterly Shear Over Keys Low Level Circulation Seems Pretty Accurate For This Morning


Wind Shear Decreasing to Favorable Levels This Evening

Good pickup there louisianaboy. Looks like 90L is trying to fight, but it is too late.
if the convection continues to fire though this could mean more rain for south louisiana than earlier expected
1519. Prgal
There is a new blog.
My thought on 92L is that it shifted east and its that spin we see NW of PR. You can see it moving west know with some sort of spin. Thats what im keeping an eye on.
Blank
48 HOUR FORECAST

This is looking like the set-up that a few of us were talking about yesterday. The trough with an area of low pressure developing south of Cuba.

I believe we could see something begin to develop from the tail of the trough, somewhere near Jamaica. If something develops, the track will depend on cyclogenesis location and how strong any high might be to the north and from the east.

Notice the front over the mid-west CONUS, it should be moving through before any storm could make landfall. But, it could also influence track, lifting it to the nGOM of wcFL.
1522. msphar
92 has looked like sheared debris clouds all week. This morning that dinky rotation nearing the Florida keys and the generalized loose rotation near 23N 67W are both looking like things worth watching. It still too early to tell for sure. Finally some substance to the rumors though murky at best.
1523. MahFL
Wow...6 area's on the experimental NHC outlook. Oh and its still pouring in Jacksonville. Where I live in Orange park I have had over 10 inches of rain in October so far.