[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081741
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EDT MON NOV 08 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...SPECIAL FEATURE...
AS OF 08/1800 UTC...SUB-TROPICAL STORM SEAN IS NOW TROPICAL
STORM SEAN CENTERED NEAR 27.7N 69.5W...OR ABOUT 490 NM SW OF
BERMUDA. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. THE
MAXIMUM SUSTAINED WIND SPEED IS 40 KTS WITH GUSTS TO 50 KTS.
SEAN IS CURRENTLY STATIONARY. FOR MORE INFORMATION SEE THE
FORECAST/ADVISORY UNDER THE AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC...AND THE PUBLIC ADVISORY LISTED UNDER THE AWIPS/WMO
HEADERS MIATCPAT4/WTNT34 KNHC. CURRENTLY...SCATTERED MODERATE
CONVECTION IS AROUND THE NRN SEMICIRCLE FROM 27N-31N BETWEEN
66W-71W.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ONLY TO THE W AFRICAN COAST AND ENDS
AT THE COASTLINE. THE ITCZ EXTENDS ALONG 6N23W 7N34W 4N48W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-11N
BETWEEN 26W-35W. SIMILAR ACTIVITY IS FROM 3N-7N BETWEEN 35W-45W.
ANOTHER AREA OF SIMILAR ACTIVITY IS FARTHER W AND E OF THE
WINDWARD ISLANDS FROM 7N-13N BETWEEN 49W-58W.

...DISCUSSION...

THE GULF OF MEXICO...
MOSTLY FAIR WEATHER IS ACROSS THE GULF OF MEXICO TODAY AROUND A
SURFACE RIDGE EXTENDING FROM A 1027 MB HIGH OVER VIRGINIA.
ANTI-CYCLONIC FLOW OF 15-20 KTS IS AROUND THE RIDGE WITH PATCHES
OF STRATOCUMULUS CLOUDS. ALOFT...AN UPPER LEVEL RIDGE EXTENDS
FROM NRN CENTRAL AMERICA ALONG 88W SUPPORTING THE SURFACE RIDGE.
A STRONG COLD FRONT CURRENTLY ACROSS THE CENTRAL CONUS WILL
ENTER THE NW GULF WITHIN TE NEXT 24 HOURS ACCOMPANIED BY
SHOWERS/THUNDERSTORMS AND STRONG WINDS BEHIND THE FRONT.

THE CARIBBEAN SEA...
AN UPPER LEVEL RIDGE COVERS THE WRN HALF OF THE CARIBBEAN SEA
EXTENDING FROM HONDURAS NWD ALONG 88W. THE ERN SIDE OF THE UPPER
RIDGE IS ACCOMPANIED BY STRONG DRY AIR WHICH IS PROVIDING MOSTLY
FAIR WEATHER ACROSS THIS PORTION OF THE BASIN. A FEW AREAS OF
ISOLATED SHOWERS ARE E OF THE YUCATAN PENINSULA AND E OF
NICARAGUA. SCATTERED SHOWERS/THUNDERSTORMS ARE IN THE SW
CARIBBEAN N OF PANAMA AND ACROSS PORTIONS OF NRN COLOMBIA NEAR
THE MONSOON TROUGH THAT EXTENDS ACROSS PANAMA TO NRN COLOMBIA.
THE ERN CARIBBEAN IS COVERED BY AN UPPER LEVEL TROUGH THAT
EXTENDS ACROSS THE WRN ATLC TO VENEZUELA WITH AXIS ALONG 68W.
MOSTLY DRY AIR ACCOMPANIES THE WRN SIDE OF THE UPPER TROUGH
MAINTAINING FAIR CONDITIONS BESIDES A FEW ISOLATED SHOWERS S OF
HISPANIOLA AND ACROSS PUERTO RICO AS WELL AS W OF THE WINDWARD
ISLANDS. DUE TO HIGHER MOISTURE VALUES PRESENT OVER THE ERN
CARIBBEAN...THERE IS THE CHANGE FOR MORE PRECIPITATION LATER IN
THE DAY AND THE TEMPERATURE RISES. MODEL DATA INDICATES THIS
AREA OF MOISTURE WILL GRADUALLY DRIFT WWD.

THE ATLANTIC OCEAN...
TROPICAL STORM SEAN IS DOMINATING THE WRN ATLC TODAY PRODUCING A
LARGE CYCLONIC WIND FIELD. WATER VAPOR IMAGERY INDICATES MOSTLY
DRY AIR AROUND THE STORM BESIDES WITHIN 150 NM OF THE CENTRAL
AND FARTHER TOT HE N WHERE MOST OF THE SHOWER ACTIVITY LIES. THE
STORM LIES UNDERNEATH AN UPPER LEVEL TROUGH ALONG 68W WHICH IS
ALSO PROVIDING DIFFLUENT FLOW ALOFT FARTHER E SUPPORTING
CLUSTERS OF SHOWERS/THUNDERSTORMS FROM 18N-30N BETWEEN 56W-63W.
A SURFACE TROUGH ALSO EXTENDS FROM N OF PUERTO RICO NEAR 19N66W
TO 24N64W DEPICTING THE CONVERGENCE OF SW WINDS FROM THE W AND
SE WINDS FROM THE E. SCATTERED SHOWERS/THUNDERSTORMS ARE ALONG
THE TROUGH AXIS. FARTHER E...AN UPPER LEVEL RIDGE EXTENDS FROM E
OF THE WINDWARD ISLANDS NEAR 11N56W TO NEAR 33N40W. AN UPPER
LEVEL TROUGH IS THE E CENTERED NEAR 15N37W WHICH MAY BE HELPING
ENHANCE CONVECTION NEAR THE ITCZ. TO THE N...A BROAD UPPER
TROUGH BETWEEN THE AZORES ISLANDS AND SPAIN IS SUPPORTING A COLD
FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N22W ALONG 27N33W
26N44W BECOMING STATIONARY TO 30N58W. SCATTERED SHOWERS/POSSIBLE
THUNDERSTORMS ARE WITHIN 90 NM EITHER SIDE OF THE FRONT. EXPECT
SEAN TO REMAIN THE DOMINATE WEATHER FEATURE ACROSS THE WRN ATLC.

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

$$
WALTON





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