[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 072348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED DEC 07 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2335 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH REMAINS INLAND ACROSS AFRICA. THE ITCZ AXIS
EXTENDS ACROSS THE COUNTRIES OF GHANA...COTE D' IVOIRE...AND
LIBERIA AND ENTERS THE ATLC WATERS ACROSS THE SOUTHERN COAST OF
SIERRA LEONE NEAR 8N13W...CONTINUING WESTWARD ALONG 8N20W 5N30W
4N40W 6N50W TO THE COAST OF FRENCH GUIANA NEAR 5N53W. SCATTERED
MODERATE CONVECTION IS FROM 2N-8N BETWEEN 27W-48W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY SHOWS A STRONG UPPER LEVEL SHORTWAVE MOVING
ACROSS THE SE CONUS SUPPORTING A COLD FRONT EXTENDING ACROSS
CENTRAL FLORIDA INTO THE GULF WATERS FROM S OF TAMPA BAY
CONTINUING SW TO 22N88W WHERE IT BECOMES STATIONARY INTO THE
YUCATAN PENINSULA NEAR THE CITY OF MERIDA. ISOLATED SHOWERS ARE
OCCURRING WITHIN 30 NM EITHER SIDE OF THE FRONT WITH MOSTLY
OVERCAST LOW LEVEL STRATOCUMULUS CLOUDS OBSERVED WITHIN 170 NM
WEST OF THE FRONT AND OVER THE REMAINDER OF THE WSW GULF
INCLUDING THE BAY OF CAMPECHE. WITHIN THIS REGION...GALE FORCE
WINDS ARE OCCURRING S OF 21N W OF FRONT...GENERATING SEAS 13 TO
15 FT. SUBSIDENCE AND CLEARING ON VISIBLE IMAGERY INDICATES A
FAIRLY STRONG SURFACE RIDGE OF HIGH PRESSURE BUILDING IN ACROSS
THE NW GULF. THE FRONT IS FORECAST TO MOVE OUT OF THE GULF
WATERS BY THURSDAY MORNING.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH IS OVER THE FAR ERN CARIBBEAN WITH AN
UPPER LOW EMBEDDED IN THE TROUGH LOCATED ABOUT 250 NM NE OF
PUERTO RICO. THIS FEATURE IS PUSHING A VERY DRY AND STABLE
AIRMASS ALOFT WEST OF A LINE EXTENDING FROM 17N62W TO 11N72W.
THIS AIRMASS ALOFT COMBINED WITH AN UPPER ANTICYCLONE CENTERED
OVER WRN CUBA IS PROVIDING MUCH OF THE CARIBBEAN WITH FAIR
WEATHER CONDITIONS AND A FEW CLUSTERS OF LOW TOP SCATTERED
SHOWERS ACROSS THE AREA. THE UPPER LEVEL TROUGHING/LOW IS
PROVIDING DIFFLUENCE ALOFT ACROSS THE FAR SOUTH-ERN CARIBBEAN
GENERATING AN AREA OF SCATTERED HEAVY SHOWERS AND THUNDERSTORMS
E OF 68W S OF 16N INCLUDING THE LESSER ANTILLES. HEAVY RAINFALL
HAS ALREADY FALLEN OVER MUCH OF THIS GROUP OF ISLANDS OVER THE
PAST WEEK. CONTINUED RAIN OVER ALREADY SATURATED TERRAIN
INCREASES THE CHANCE FOR FLASH FLOODING...ESPECIALLY OVER THE
HIGHER TERRAIN. THE UPPER LEVEL LOW IS FORECAST TO SLOWLY LIFT
NORTHWARD INTO THE SW NORTH ATLC WATERS AS A WEAK UPPER LEVEL
RIDGE MOVES OVER THE CENTRAL CARIBBEAN ALONG 70W.

ATLANTIC OCEAN...
SURFACE HIGH PRESSURE INFLUENCE CONTINUES W OF 60W ON THE
SOUTHERN PERIPHERY OF A 1023 MB HIGH CENTERED NE OF BERMUDA NEAR
34N60W. A NARROW UPPER LEVEL TROUGH AXIS EXTENDS SOUTHWARD FROM
THE CENTRAL ATLC INTO THE FAR ERN CARIBBEAN SEA. AN UPPER LEVEL
LOW IS EMBEDDED IN THIS TROUGHING CENTERED ABOUT 250 NM NE OF
PUERTO RICO. THIS UPPER LEVEL SYSTEM SUPPORTS A 1009 MB LOW
CENTERED NEAR 22N53W WITH A LENGTHY SURFACE TROUGH EXTENDING NE
TO 32N42W AND SW TO JUST E OF THE WINDWARD ISLANDS NEAR 14N60W.
LOW-LEVEL CONVERGENCE AROUND THESE SURFACE FEATURES IN
COMBINATION WITH MIDDLE TO UPPER LEVEL DIFFLUENCE FLOW
ASSOCIATED TO THE UPPER TROUGHING IS GENERATING A BROAD AREA OF
SCATTERED HEAVY SHOWERS AND THUNDERSTORMS WITHIN 120-160 NM
EITHER SIDE OF THE SURFACE TROUGH/LOW. ACROSS THE REMAINDER OF
THE CENTRAL AND ERN BASIN...A STRONG SURFACE RIDGE ANCHORED BY A
1033 MB HIGH CENTERED WEST OF PORTUGAL NEAR 40N15W CONTINUES TO
INFLUENCE MUCH OF THE EASTERN ATLC. AN APPROACHING COLD FRONT
WILL ENTER THE FAR SW NORTH ATLC WATERS OVER TH NEXT 3-6 HOURS
WITH STRONG NORTHWESTERLY WINDS BEHIND IT.

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

$$

GARCIA




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