[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 290559
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU SEP 29 2011

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED NEAR 19.4N 60.7W AT 29/0300
UTC OR ABOUT 155 NM E-NE OF THE NORTHERN LEEWARD ISLANDS MOVING
NW AT 5 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB.
MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT.
PLEASE SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/ WTNT21 KNHC FOR MORE DETAILS. OPHELIA HAS STRENGTHEN
TODAY DESPITE BEING UNDER SOUTHWESTERLY SHEAR WITH SCATTERED
MODERATE/ ISOLATED STRONG CONVECTION WITHIN 90 NM OF LINE FROM
16N58W 19N58W TO 21N60W AND SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS COVERING THE REMAINDER OF THE AREA FROM 14N-23N
BETWEEN 57-62W INCLUDING THE LESSER ANTILLES.

TROPICAL STORM PHILIPPE IS CENTERED NEAR 17.4N 40.8W AT 29/0300
UTC OR ABOUT 970 NM W OF THE CAPE VERDE ISLANDS MOVING W-NW AT 11
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM
SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. PLEASE SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/
WTNT22 KNHC FOR MORE DETAILS. PHILIPPE REMAINS UNDER SOUTHERLY
SHEAR WITH SCATTERED MODERATE/STRONG CONVECTION FROM 17N-21N
BETWEEN 38W-42W.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED ALONG 30W BETWEEN 4N-11N MOVING W NEAR
10 KT. WAVE IS DIFFICULT TO DISCERN IN SATELLITE IMAGERY BUT IS
EVIDENT IN THE UPPER LEVEL SATELLITE WINDS. NO ASSOCIATED
SHOWERS/CONVECTION.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA ENTERING THE E TROPICAL
ATLC NEAR 17N16W TO 14N25W. SMALL CLUSTERS OF SCATTERED MODERATE
CONVECTION ARE FROM 3N-7N BETWEEN 11W-26W AND FROM 1N-4N BETWEEN
32W-42W.

...DISCUSSION...

GULF OF MEXICO...
THE LARGE UPPER LOW REMAINS CENTERED OVER THE GREAT LAKES
EXTENDING A BROAD UPPER TROUGH INTO THE N GULF N OF 29N
SUPPORTING A FRONTAL BOUNDARY THAT REMAINS INLAND OVER THE SE
CONUS AND PRODUCING AN OUTFLOW BOUNDARY THAT AT 29/0300 UTC
EXTENDS FROM 27N89W TO OVER LOUISIANA NEAR LAKE CHARLES
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM
ALONG THIS BOUNDARY. A SURFACE TROUGH AT 29/0300 UTC IS OVER
FLORIDA EXTENDING FROM JACKSONVILLE TO TAMPA THEN S TO FORT
MYERS INTO FLORIDA BAY TO NEAR 25N82W WITH SCATTERED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS WITHIN 30 NM OF THE TROUGH. A
BROAD UPPER RIDGE COVERS THE REMAINDER OF THE GULF ANCHORED OVER
THE E PACIFIC REGION GIVING THE GULF WATERS NEAR WESTERLY FLOW
ALOFT. MOSTLY CLEAR SKIES DOMINATE THE REMAINDER OF THE GULF
TONIGHT WITH THE EXCEPTION OF FAST MOVING HIGH CLOUDS. WEAK HIGH
PRESSURE WILL DRIFT NW THROUGH FRI. A COLD FRONT WILL MOVE INTO
THE N GULF FRI NIGHT EXTENDING FROM TAMPA BAY FLORIDA TO SE
TEXAS LATE FRI NIGHT THEN WILL STALL FROM THE STRAITS OF FLORIDA
TO THE YUCATAN SUN. STRONG HIGH PRESSURE WILL BUILD SE BEHIND
THE FRONT ACROSS THE N CENTRAL GULF.

CARIBBEAN SEA...
THE PRIMARY CONCERN AGAIN TONIGHT IS TROPICAL STORM OPHELIA NE
OF THE LEEWARD ISLANDS AND THE ACTIVITY OVER THE LESSER
ANTILLES...SEE SPECIAL FEATURE SECTION ABOVE. THE UPPER RIDGE
OVER THE GULF OF MEXICO EXTENDS OVER THE W CARIBBEAN W OF 70W
PROVIDING A DIFFLUENT ENVIRONMENT TO GENERATE ISOLATED CLUSTERS
OF SHOWERS/THUNDERSTORMS N OF A LINE FROM 17N70W ACROSS JAMAICA
TO THE W TIP OF CUBA. THE MONSOON TROUGH EXTENDS FROM COLOMBIA
NEAR 9N76W ACROSS E PANAMA INTO THE E PACIFIC REGION OVER
NICARAGUA NEAR 12N84W BUT IS NOT GENERATING ANY SHOWER ACTIVITY
IN THE SW CARIBBEAN. THIS IS LEAVING THE REMAINDER OF THE
CARIBBEAN UNDER MOSTLY CLEAR SKIES AGAIN TONIGHT. A WEAK
PRESSURE PATTERN WILL EXIST OVER THE CARIBBEAN THROUGH SUN.

ATLANTIC OCEAN...
THE PRIMARY CONCERN TONIGHT IS TROPICAL STORM OPHELIA NE OF
THE LEEWARD ISLANDS AND TROPICAL STORM PHILIPPE OVER THE CENTRAL
ATLC...SEE SPECIAL FEATURE SECTION ABOVE. AN UPPER RIDGE COVERS
THE W ATLC EXTENDING FROM THE N COAST OF CUBA NEAR 22N75W TO
BEYOND 30N72W PROVIDING A DIFFLUENT ENVIRONMENT ALOFT TO
GENERATE ISOLATED SHOWERS/THUNDERSTORMS OVER THE BAHAMA ISLANDS.
AN ELONGATED UPPER TROUGH EXTENDS FROM BERMUDA THROUGH AN UPPER
LOW NEAR 28N63W TO THE E OF TROPICAL STORM OPHELIA NEAR 21N64W.
A WEAK SURFACE RIDGE DOMINATES THE W INTO THE CENTRAL ATLC N OF
26N BETWEEN 55W-80W ANCHORED BY 1019 MB HIGH OVER BERMUDA. AN
UPPER TROUGH EXTENDS S INTO THE CENTRAL ATLC N OF 26N BETWEEN
35W-55W SUPPORTING A COLD FRONT N OF THE DISCUSSION AREA AND A
PAIR OF SURFACE TROUGHS...THE EASTERN ONE EXTENDING FROM 30N38W
TO 25N50W GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS WITHIN 120 NM E OF THE TROUGH AND SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM OF LINE FROM 30N36W
TO BEYOND 32N30W. THE WESTERN SURFACE TROUGH EXTENDS FROM 31N45W
29N50W TO 30N53W GENERATING SCATTERED SHOWERS AND POSSIBLE
ISOLATED THUNDERSTORMS WITHIN 60 NM SE OF THE TROUGH E OF 48W. A
SURFACE RIDGE COVERS THE E ATLC ANCHORED BY A PAIR OF 1022 MB
HIGHS...ONE NNE OF THE MADEIRA ISLANDS AND A SECOND NEAR 29N22W.
HIGH PRESSURE OVER THE W ATLC WILL REMAIN STATIONARY THROUGH THU
MOVING NE FRI AND SAT. A WEAK FRONT WILL MOVE INTO THE FAR W
ATLC THU AND FRI STALLING OFF THE FLORIA COAST ON FRI EVENING. A
STRONGER FRONT WILL MOVE INTO THE FAR W ATLC FRI NIGHT RAPIDLY
MOVING E AND MERGING WITH THE STALLED FRONT EXTENDING FROM NEAR
BERMUDA TO THE SE BAHAMAS SUN THEN STALLING OUT OVER CENTRAL
ATLC MON.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
PAW





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