000 AXNT20 KNHC 280548 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST WED DEC 28 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 0535 UTC. ...ITCZ/MONSOON TROUGH... A GREAT PORTION OF THE MONSOON TROUGH REMAINS INLAND OVER AFRICA. A SMALL SECTION OF IT ENTERS THE ATLC THROUGH THE COAST OF SIERRA LEONE ALONG 8N10W AND QUICKLY ENDS AT 6N17W. THE ITCZ AXIS EXTENDS WSW FROM THIS POINT ALONG 3N25W 2N35W TO THE COAST OF BRAZIL NEAR 1S47W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 200 NM ON THE NRN SIDE OF THE ITCZ AXIS BETWEEN 18W-40W. ...DISCUSSION... GULF OF MEXICO... THE COLD FRONT THAT HAS BEEN MOVING ACROSS THE GULF THESE PAST FEW DAYS IS NOW IN THE WRN ATLC BASIN. HOWEVER...SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS ARE STILL MOVING THROUGH THE STRAITS OF FLORIDA THIS LATE EVENING. SIMILAR ACTIVITY LINGERS OVER THE BAY OF CAMPECHE S OF 20N. THE REMAINDER OF THE GULF IS UNDER THE INFLUENCE OF MOSTLY DRY WSW FLOW ALOFT AND A SURFACE RIDGE ANCHORED BY A 1023 MB HIGH CENTERED OVER ERN TEXAS. NORTHERLY WINDS ARE EXPECTED TO PERSIST WITH WEATHER CONDITIONS REMAINING FAIR THROUGH EARLY THURSDAY. CARIBBEAN SEA... VERY DRY AIR ALOFT AND STRONG SUBSIDENCE COVERS MOST OF THE CARIBBEAN WATERS THIS LATE EVENING. THIS AIRMASS IS SUPPRESSING DEEP CONVECTION ACROSS THE DISCUSSION AREA. HOWEVER...A FEW SHOWERS ARE OVER THE FAR NW BASIN INCLUDING THE YUCATAN CHANNEL IN THE VICINITY OF THE SRN EXTENSION OF THE WRN ATLC COLD FRONT. FRESH TO STRONG TRADE WIND FLOW CONTINUES ACROSS MUCH OF THE BASIN...ESPECIALLY BETWEEN 68W-80W AND NEAR THE COAST OF COLOMBIA...WITH A FEW SMALL CLUSTERS OF LOW-TOP WEAK SHOWERS EMBEDDED IN THE FLOW. THESE CONDITIONS ARE EXPECTED TO PERSIST THROUGH FRIDAY AS A RIDGE WILL POSITION ITSELF IN THE SW NORTH ATLC AND INCREASE THE TRADES DUE TO AN INCREASED PRESSURE GRADIENT. THE TRADES WILL REMAIN STRONG BASIN-WIDE THROUGH THE UPCOMING WEEKEND. ATLANTIC OCEAN... A LONGWAVE UPPER LEVEL TROUGH IS MOVING OFF THE CONUS SEABOARD SUPPORTING A COLD FRONT ANALYZED INTO THE DISCUSSION AREA ALONG 32N75W TO THE SRN FLORIDA COAST NEAR 26N80W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 100 NM EAST OF THE FRONT. THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF A 1024 MB SURFACE HIGH CENTERED NEAR 28N62W. FARTHER EAST...AN UPPER LEVEL LOW IS NOTED ON WATER VAPOR IMAGERY CENTERED NORTH OF THE DISCUSSION AREA NEAR 40N50W. THIS UPPER LEVEL FEATURE SUPPORTS AN OCCLUDED BUT STRONG LOW PRESSURE SYSTEM THAT EXTENDS A COLD FRONT INTO THE AREA ALONG 32N44W TO 25N50W TO 23N55W THEN IT CONTINUES W AS A DISSIPATING COLD FRONT TO 25N68W. WITH MOISTURE REMAINING LIMITED WITH THIS FRONT...ONLY POSSIBLE ISOLATED SHOWERS ARE WITHIN 70 NM E OF THE BOUNDARY. THE MAIN IMPACT WITH THIS FRONT IS GALE FORCE NW WINDS N OF 30N W OF FRONT GENERATING SEAS BETWEEN 12-24 FT. THESE CONDITIONS ARE EXPECTED TO DECREASE BELOW GALE WARNING CRITERIA OVER THE NEXT 6-9 HOURS. A WEAK AREA OF LOW LEVEL CONFLUENCE OF LIGHT WINDS IS ANALYZED AS A WEAK SURFACE TROUGH FROM 22N47W TO 14N50W WITHOUT ANY RAINSHOWER ACTIVITY ASSOCIATED. THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF AN UPPER LEVEL LOW CENTERED NEAR 21N27W. MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO BE DRAWN ACROSS THE FAR ERN ATLC WITH ISOLATED SHOWERS OCCURRING FROM 10N-21N E OF 23W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA