000 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