000 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