[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 050004
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN OCT 04 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 40W/41W TO THE SOUTH OF
15N MOVING WESTWARD 15 KT. A LARGE CYCLONIC ENVELOPE FROM THE
SURFACE UPWARD COVERS THE AREA FROM THE ITCZ TO 17N BETWEEN 35W
AND 47W. IT LOOKS LIKE TWO OR THREE DISTINCT AXES OF LOW
PRESSURE MAY BE SPOTTED IN VISIBLE IMAGERY. STRONG SHOWERS AND
THUNDERSTORMS FROM 9N TO 15N BETWEEN 39W AND 45W. SCATTERED
MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS FROM 5N TO 10N
BETWEEN 31W AND 37W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 54W/55W TO THE SOUTH OF
15N MOVING WESTWARD 15 KT. AN UPPER LEVEL TROUGH APPEARS TO BE
NEARLY CO-LOCATED WITH THE WAVE. SCATTERED MODERATE TO STRONG
SHOWERS AND THUNDERSTORMS COVER THE AREA FROM 9N TO 14N BETWEEN
50W AND 60W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 77W/78W TO THE SOUTH OF
17N MOVING WESTWARD 15 KT. THIS WAVE IS MOVING THROUGH THE AREA
OF AN UPPER LEVEL TROUGH. NEARBY SHOWERS MAY BE MORE RELATED
TO THE UPPER LEVEL TROUGH THAN TO THE WAVE.

...THE ITCZ...

7N12W 4N20W 9N32W 8N44W 9N54W INTO NORTHEASTERN VENEZUELA NEAR
8N62W. ISOLATED MODERATE SHOWERS FROM 5N TO 10N BETWEEN AFRICA
AND 30W. THE REST OF THE PRECIPITATION ANYWHERE NEAR THE ITCZ
IS RELATED TO THE TWO TROPICAL WAVES.

...DISCUSSION...

THE GULF OF MEXICO...
AN UPPER LEVEL RIDGE EXTENDS FROM THE ISLAS MARIAS ALONG THE
WEST COAST OF MEXICO...THE CENTRAL GULF OF MEXICO...BEYOND THE
FLORIDA BIG BEND. BROAD UPPER LEVEL ANTICYCLONIC WIND FLOW IS
BEING SPREAD ACROSS THE ENTIRE AREA. SOME OF THIS ANTICYCLONIC
FLOW EVEN CROSSES FLORIDA COVERS THE ATLANTIC OCEAN TO THE WEST
OF 70W...AND IT GOES INTO THE CARIBBEAN SEA TO THE WEST OF 80W.
A STATIONARY FRONT STRADDLES 30N BETWEEN 78W AND THE FLORIDA
BIG BEND. A WARM FRONT CONTINUES NORTHWESTWARD FROM THE FLORIDA
BIG BEND INTO MISSISSIPPI AND LOUISIANA. THE SURFACE PRESSURE
GRADIENT IS WEAK. BROKEN TO OVERCAST MULTILAYERED CLOUDS AND
SHOWERS ARE TO THE NORTH OF 29N BETWEEN THE FLORIDA BIG BEND
AND 96W IN EAST TEXAS.

THE CARIBBEAN SEA...
UPPER LEVEL ANTICYCLONIC FLOW FROM THE GULF OF MEXICO SPILLS
INTO THE CARIBBEAN SEA TO THE WEST OF 80W. AN UPPER LEVEL
TROUGH ENTERS THE AREA THROUGH THE SOUTHERN BAHAMAS AND THE
WINDWARD PASSAGE...TO THE SOUTHWESTERN CORNER OF THE AREA.
THE TROUGH IS ABOUT 330 NM WIDE. AN UPPER LEVEL RIDGE ALONG
THE LINE FROM WESTERN VENEZUELA TO THE MONA PASSAGE IS
IMMEDIATELY TO THE EAST OF THE TROUGH. UPPER LEVEL CYCLONIC
FLOW CUTS INTO THE NORTHEASTERN CORNER OF THE AREA. A SURFACE
TROUGH GOES FROM 22N60W TO 19N62W TO 16N62W. ISOLATED MODERATE
SHOWERS FROM 17N TO 19N BETWEEN 61W AND 63W. STRONG SHOWERS/
THUNDERSTORMS ARE CONFINED TO THE AREA FROM 13N TO 14N WITHIN
30 NM ON EITHER SIDE OF 76W. OTHER AREAS OF BROKEN TO OVERCAST
MULTILAYERED CLOUDS AND POSSIBLE SHOWERS ARE WITHIN 240 NM TO
300 NM ON EITHER SIDE OF THE TROUGH.

THE ATLANTIC OCEAN...
UPPER LEVEL ANTICYCLONIC FLOW CROSSES FLORIDA FROM THE GULF OF
MEXICO AND THE COVERS THE AREA TO THE WEST OF 70W. AN UPPER
LEVEL TROUGH...PASSING THROUGH A SPOT THAT IS JUST TO THE WEST
OF BERMUDA TO 28N67W...CROSSING THE SOUTHERN BAHAMAS AND THROUGH
THE WINDWARD PASSAGE. A WEAK UPPER LEVEL CYCLONIC CENTER IS NEAR
20N65W. THE WEAKER CENTER IS MORE CLOSELY RELATED TO THE UPPER
LEVEL CYCLONIC FLOW IN THE NORTHEASTERN CORNER OF THE CARIBBEAN
SEA. AN UPPER LEVEL TROUGH PASSES THROUGH 32N25W TO 29N32W. THIS
FEATURE SUPPORTS A SURFACE TROUGH WHOSE SOUTHERNMOST POINT IS
31N30W. ISOLATED SHOWERS AND POSSIBLE THUNDERSTORMS ARE WITHIN
30 NM ON EITHER SIDE OF 28N24W 30N22W 31N19W. A SEPARATE CYCLONIC
CIRCULATION CENTER IS NEAR 26N53W. A LINE OF SHOWERS DEVELOPED
SIX HOURS AGO ALONG THE LINE FROM 27N42W TO 24N50W TO 21N60W AND
21N62W. THE CLOUD TOP TEMPERATURES IN THIS LINE OF PRECIPITATION
HAVE BEEN WARMING DURING THE LAST SIX HOURS EVEN THOUGH IT IS
POSSIBLE THAT SOME SHOWERS STILL REMAIN.

$$
MT





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