000 AXNT20 KNHC 211748 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST WED DEC 20 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1700 UTC. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS INLAND OVER W AFRICA TO THE COAST OF LIBERIA NEAR 6N11W CONTINUING TO 6N13W. THE ITCZ CONTINUES FROM 6N13W ALONG 5N20W 6N29W 4N37W 6N49W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 4N-7N BETWEEN 14W-28W...AND FROM 6N-7N BETWEEN 43W-49W. ...DISCUSSION... GULF OF MEXICO... A FRONTAL BOUNDARY CONTINUES TO IMPACT THE N AND WRN PORTIONS OF THE GULF OF MEXICO TODAY WITH A COLD SECTION EXTENDING FROM THE MISSISSIPPI COAST NEAR 30N90W ACROSS SE LOUISIANA TO 28N92W WHERE IT BECOMES STATIONARY AND CONTINUES ALONG 25N96W 21N97W 23N100W. AN AREA OF WIDESPREAD SHOWERS/ISOLATED THUNDERSTORMS IS AHEAD OF THE FRONT IMPACTING THE NE CORNER OF THE GULF N OF 28N BETWEEN 83W-89W. POSSIBLE ISOLATED SHOWERS ARE ALSO ALONG THE FRONTAL BOUNDARY. THE ERN GULF REMAINS UNDER SURFACE RIDGING EXTENDING FROM A HIGH PRESSURE SYSTEM IN THE W ATLC. THIS PATTERN IS PROVIDING MAINLY SE-S FLOW AHEAD OF THE FRONT. DUE TO THE STRONG PRESSURE GRADIENT BETWEEN THE FRONT AND THE HIGH...WIND SPEEDS ARE BETWEEN 15-20 KTS WITH HIGHER GUSTS. ALOFT...MAINLY SWLY FLOW DOMINATES WITH A WEAK SHORTWAVE TROUGH EMBEDDED IN THE FLOW NEAR THE W COAST OF FLORIDA WHICH IS ENHANCING THE SHOWER ACTIVITY IN THE NE GULF. BESIDES THE MOISTURE PRESENT NEAR THE AFOREMENTIONED SHOWER ACTIVITY...THE REMAINDER OF THE BASIN IS COVERED BY DRY AIR ALOFT WHICH IS HELPING PROVIDE FAIR CONDITIONS ACROSS MUCH OF THE SRN GULF. EXPECT THE NRN PORTION OF THE FRONT TO CONTINUE TO MOVE EWD WHILE THE STATIONARY PART RETREATS TO THE NW BEFORE A SECOND COLD FRONT MOVES INTO THE NW GULF TOMORROW. CARIBBEAN SEA... WINDY CONDITIONS ARE ACROSS THE CARIBBEAN TODAY WITH MAINLY NE-E TRADEWIND FLOW OF 20-25 KTS REACHING 30 KTS IN THE CENTRAL CARIBBEAN AND GALE FORCE NEAR THE COAST OF COLOMBIA. ISOLATED SHOWERS ARE EMBEDDED WITHIN THE TRADEWIND FLOW WITH SOME STRONGER ACTIVITY N OF VENEZUELA. ALOFT...A WEAK SHORTWAVE UPPER TROUGH IS OVER THE FAR NW CARIBBEAN EXTENDING FROM JUST W OF FLORIDA. UPPER RIDGING COVERS THE REMAINDER OF THE AREA WITH AXIS EXTENDING FROM THE FAR SE CORNER OF THE BASIN TO HISPANIOLA AND INTO THE W ATLC. SURFACE HIGH PRESSURE OVER THE W ATLC IS EXPECTED TO REMAIN STATIONARY WHICH WILL CAUSE THE STRONG PRESSURE GRADIENT...AND THUS HIGH WINDS...TO PERSIST OVER THE CARIBBEAN FOR THE NEXT COUPLE DAYS. ATLANTIC OCEAN... SURFACE RIDGING AROUND A 1028 MB HIGH NEAR 31N68W IS PROVIDING MOSTLY FAIR WEATHER ACROSS THE WRN ATLC. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE WITH AXIS ALONG 74W. AN UPPER LEVEL TROUGH TO THE E ALONG 40W CONTINUES TO SUPPORT A FRONTAL BOUNDARY IN THE CENTRAL ATLC. THE NRN PORTION OF THE FRONT HAS REMAINED STATIONARY ALONG 32N38W TO 29N40W BECOMING COLD ALONG 23N45W 21N50W DISSIPATING TO 19N55W. SCATTERED SHOWERS ARE MAINLY E OF THE FRONT N OF 25N BETWEEN 35W-40W. ISOLATED SHOWERS ARE ALONG THE FRONT ELSEWHERE. FARTHER S...AN AREA OF ACTIVE WEATHER IS JUST E OF THE SRN WINDWARD ISLANDS FROM 10N-12N BETWEEN 53W-62W DUE TO WIND SPEED CONVERGENCE. THE REMAINDER OF THE BASIN IS INFLUENCED BY SURFACE RIDGING AROUND A 1036 MB HIGH NE OF THE AZORES ISLANDS NEAR 43N13W PROVIDING GENERALLY FAIR WEATHER ACROSS THE ERN ATLC. ALOFT...AN UPPER LEVEL RIDGE CENTERED NEAR 44N15W IS SUPPORTING THE SURFACE RIDGE. AN ELONGATED UPPER TROUGH IS THE S BETWEEN THE CAPE VERDE AND CANARY ISLANDS CAUSING NO SIGNIFICANT WEATHER. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON