000 AXNT20 KNHC 310543 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0500 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF LIBERIA NEAR 6N11W CONTINUING TO 5N14W. THE ITCZ CONTINUES FROM 5N14W ALONG 3N25W 2N34W 2N43W EQ50W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM EITHER SIDE THE AXIS BETWEEN 11W-16W. SIMILAR ACTIVITY IS FROM 3N-5N BETWEEN 30W-39W. SOME OF THIS ACTIVITY IS INFLUENCE 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 TONIGHT 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 1020 MB HIGH NEAR 26N87W IS HELPING CONTRIBUTE TO THE FAIR WEATHER. SATELLITE IMAGERY INDICATES A SMALL AREA OF FOG ALONG THE TEXAS 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 IS BEGINNING TO MOVE ACROSS THE NRN GULF...CURRENTLY OVER LOUISIANA...WHICH IS SUPPORTING A COLD FRONT N OF THE AREA. COMPUTER GUIDANCE INDICATES THAT THE FRONT WILL STAY N OF THE AREA...AND WEAK SURFACE RIDGE WILL REMAIN ACROSS THE BASIN THROUGH LATE SATURDAY/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 TONIGHT WITH AXIS ALONG 66W. WATER VAPOR IMAGERY ALSO INDICATES DRY AIR ACCOMPANYING THE RIDGE WHICH IS LIMITING CONVECTION. A FEW ISOLATED SHOWERS ARE NOTED FROM 16N-20N BETWEEN 73W-76W...AND FROM 17N-18N BETWEEN 62W-66W. 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 1041 MB HIGH JUST E OF THE AZORES ISLANDS WITH AXIS EXTENDING WSW ALONG 32N50W 29N66W TO SE FLORIDA. HOWEVER...A WEAKNESS IN THE UPPER RIDGE ALONG 66W IS SUPPORTING A SURFACE TROUGH ALONG 25N70W TO 20N72W WITH SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS TO THE E FROM 23N-28N BETWEEN 65W-68W. THE REMNANTS OF A STATIONARY FRONT ALSO STILL REMAIN ALONG 32N65W 28N72W 24N75W 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 18N38W 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 THROUGHOUT THE NEXT 12 HOURS BEFORE A COLD FRONT ENTERS THE W ATLC WATERS LATER THIS AFTERNOON/EVENING. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON