[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 311141
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SAT DEC 31 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1100 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
LIBERIA NEAR 5N9W CONTINUING TO 4N16W. THE ITCZ CONTINUES FROM
4N16W ALONG 3N28W 3N46W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 3N-6N BETWEEN 11W-16W. SIMILAR ACTIVITY IS
FROM 3N-6N BETWEEN 24W-33W. SOME OF THIS ACTIVITY IS INFLUENCED
BY AN UPPER LEVEL LOW TO THE N NEAR 19N37W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY CONTINUES TO SHOW MOSTLY DRY AIR ALOFT IN
WSW FLOW ACROSS THE GULF OF MEXICO AROUND A BROAD UPPER RIDGE
COVERING THE CARIBBEAN AND W ATLC...WHICH IS HELPING MAINTAIN
MOSTLY FAIR SURFACE CONDITIONS WITH LIGHT WINDS AND CLEAR SKIES
BASIN-WIDE. WEAK SURFACE RIDGING AROUND A 1021 MB HIGH NEAR
27N89W IS HELPING CONTRIBUTE TO THE FAIR WEATHER. SATELLITE
IMAGERY INDICATES AN AREA OF FOG ALONG THE TEXAS AND LOUISIANA
COASTLINE. A WEAK SURFACE TROUGH EXTENDS DOWN THE YUCATAN
PENINSULA WHICH IS SUPPORTING A FEW ISOLATED SHOWERS JUST N OF
THE LANDMASS. A SHORTWAVE UPPER TROUGH PREVIOUSLY OVER LOUISIANA
HAS QUICKLY MOVED E AND NOW IS JUST N OF FLORIDA. THE UPPER
TROUGH SUPPORTS A NOW STATIONARY FRONT N OF THE AREA. COMPUTER
GUIDANCE INDICATES THAT THE FRONT WILL STAY N OF THE AREA...AND
WEAK SURFACE RIDGING WILL REMAIN ACROSS THE BASIN THROUGH LATE
TONIGHT/EARLY SUNDAY BEFORE THE NEXT COLD FRONT MOVES OFF THE
TEXAS COAST INTO THE NW GULF WITH STRONG NE WINDS BEHIND IT.

CARIBBEAN SEA...
A BROAD UPPER RIDGE IS ACROSS THE CARIBBEAN THIS MORNING WITH
AXIS ALONG 66W. WATER VAPOR IMAGERY ALSO INDICATES DRY AIR
ACCOMPANYING THE RIDGE WHICH IS LIMITING CONVECTION. A FEW
ISOLATED SHOWERS ARE NOTED S OF PUERTO RICO AND ACROSS JAMAICA.
THE REMAINDER OF THE BASIN HAS MOSTLY CLEAR SKIES. NE-E
TRADEWIND FLOW OF 20-25 KTS IS ACROSS THE AREA REACHING 30 KTS
IN THE FAR ERN CARIBBEAN AND THE SW CARIBBEAN NEAR THE COAST OF
COLOMBIA. THE STRONG PRESSURE GRADIENT BETWEEN HIGH PRESSURE
ACROSS THE GULF AND W ATLC AND LOWER PRESSURES OVER S AMERICA IS
HELPING MAINTAIN THE STRONG WINDS. THIS WILL PERSIST THROUGH THE
WEEKEND UNTIL A FRONT MOVES THROUGH THE GULF OF MEXICO ON SUNDAY
AND INTO THE W ATLC ALLOWING THE PRESSURE GRADIENT TO RELAX.

ATLANTIC OCEAN...
BROAD UPPER LEVEL RIDGING DOMINATES THE MAJORITY OF THE ATLC
WHICH IS HELPING SUPPORT A BROAD SURFACE RIDGE EXTENDING FROM A
1039 MB HIGH JUST SE OF THE AZORES ISLANDS WITH AXIS EXTENDING
WSW ALONG 32N50W 28N65W. HOWEVER...A WEAKNESS IN THE UPPER RIDGE
ALONG 66W IS SUPPORTING A SURFACE TROUGH ALONG 27N67W TO 23N70W
WITH SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS TO THE E FROM
26N-29N BETWEEN 62W-68W. THE REMNANTS OF A FRONTAL
BOUNDARY...NOW LIFTING N ALSO REMAIN ALONG 29N74W 32N69W WITH NO
ASSOCIATED SHOWER ACTIVITY. THIS BOUNDARY IS EXPECTED TO
CONTINUE TO DISSIPATE DUE TO THE LACK OF UPPER LEVEL SUPPORT.
THE REMAINDER OF THE BASIN IS DOMINATED BY THE AFOREMENTIONED
SURFACE HIGH NEAR THE AZORES ISLANDS MAINTAINING MOSTLY FAIR
WEATHER. HOWEVER...AN UPPER LEVEL LOW IS S OF THE SURFACE HIGH
CENTERED NEAR 19N37W PROVIDING DIFFLUENCE ALOFT ACROSS THE SE
ATLC WHICH IS HELPING SUPPORT UPPER LEVEL CLOUDS AND SOME
CONVECTION NEAR THE ITCZ. THE SURFACE RIDGE WILL REMAIN THE
DOMINANT FEATURE BEFORE A COLD FRONT ENTERS THE W ATLC WATERS
LATER THIS AFTERNOON/EVENING.

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

$$
WALTON






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