000 AXNT20 KNHC 152338 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU DEC 15 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 2300 UTC. ...THE ITCZ/THE MONSOON TROUGH... THE ITCZ EXTENDS ACROSS FAR WRN AFRICA TO THE COAST OF LIBERIA NEAR 6N11W CONTINUING ALONG 6N20W 4N30W 4N39W. ISOLATED MODERATE CONVECTION IS WITHIN 250 NM N OF THE AXIS BETWEEN 20W-39W. ...DISCUSSION... THE GULF OF MEXICO... MOSTLY FAIR WEATHER IS ACROSS THE GULF OF MEXICO THIS EVENING DUE TO SURFACE RIDGING AROUND A PAIR OF 1026 MB HIGHS OFF THE SE UNITED STATES COAST WITH AXIS EXTENDING FROM NE FLORIDA TO THE BAY OF CAMPECHE. MAINLY SE FLOW OF 10-15 KTS IS AROUND THE RIDGE WITH A FEW AREAS OF LOW-LEVEL CLOUDS AND POSSIBLE ISOLATED SHOWERS ESPECIALLY IN THE SE AND NW CORNERS OF THE BASIN. ALOFT...AN UPPER LEVEL RIDGE COVERS THE AREA WITH AXIS EXTENDING JUST E OF THE FLORIDA PENINSULA ALONG 79W. MOSTLY DRY AIR ACCOMPANIES THE UPPER RIDGE WHICH IS HELPING MAINTAIN THE FAIR SURFACE CONDITIONS. SURFACE RIDGING IS EXPECTED TO REMAIN OVER THE ERN HALF OF THE BASIN WITH A COLD FRONT APPROACHING THE NW CORNER EXPECTED TO MOVE OVER THE GULF WATERS OVERNIGHT WITH STRONGER NLY WINDS UP TO 20 KTS BEHIND IT. THE CARIBBEAN SEA... MUCH OF THE NW CARIBBEAN IS EXPERIENCING MOSTLY FAIR WEATHER DUE TO DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE EXTENDING FROM NW VENEZUELA TO WRN CUBA. THIS PATTERN IS ALSO PROVIDING DIFFLUENCE ALOFT OVER THE SW CARIBBEAN BETWEEN THE UPPER RIDGE AND A HORIZONTALLY ALIGNED UPPER TROUGH OVER THE ERN PACIFIC. DIFFLUENCE ALOFT COMBINED WITH SURFACE CONVERGENCE NEAR THE MONSOON TROUGH EXTENDING ACROSS COSTA RICA TO NRN COLOMBIA IS HELPING PRODUCE SCATTERED SHOWERS/THUNDERSTORMS S OF 13N BETWEEN 73W-85W. A DISSIPATING COLD FRONT IS MOVING ACROSS THE ERN CARIBBEAN FROM 17N63W TO 15N77W SUPPORTING ISOLATED SHOWERS WITHIN 75 NM EITHER SIDE OF THE AXIS ALONG WITH SLIGHTLY STRONGER NELY WINDS UP TO 25 KTS TO THE N OF THE AXIS. A SURFACE TROUGH IS TO THE S ALONG 13N61W TO 12N69W WITH ISOLATED SHOWERS WITHIN 50 NM TO THE S OF THE AXIS. EXPECT THE FRONT TO DISSIPATE WITHIN THE NEXT 24 HOURS WITH WINDS UP TO 25 KTS REMAINING OVER THE CENTRAL CARIBBEAN. THE ATLANTIC OCEAN... UPPER LEVEL RIDGING COVERS THE FAR WRN ATLC SUPPORTING A PAIR OF 1026 MB SURFACE HIGHS NEAR 32N81W AND 33N73W WHICH ARE PROVIDING MOSTLY FAIR WEATHER ACROSS THE WRN ATLC. A NARROW UPPER LEVEL TROUGH IS ALONG 54W SUPPORTING A COLD FRONT ALONG 32N48W 21N56W 17N6W. GALE FORCE WINDS ARE NOTED TO THE E OF THE FRONT TO 44W N OF 28N. MOST OF THE SHOWER ACTIVITY IS ALSO TO THE E UNDER THE AREA OF DIFFLUENCE ALOFT. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 12N BETWEEN 44W-52W. A SURFACE TROUGH IS S OF THE FRONTAL BOUNDARY ALONG 23N52W 16N53W 13N61W. POSSIBLE ISOLATED SHOWERS ARE ALONG THE AXIS. FARTHER E...UPPER LEVEL RIDGING COVERS THE MAJORITY OF THE E ATLC CENTERED NEAR 35N21W SUPPORTING A 1033 MB HIGH NEAR 36N11W WHICH IS PROVIDING FAIR WEATHER ACROSS MUCH OF THE AREA E OF 43W. AN UPPER LEVEL LOW IS SOUTH OF THE UPPER RIDGE CENTERED NEAR 23N26W. AN UPPER LEVEL JET TO THE S OF THE UPPER LOW CENTER IS SUPPORTING SOME UPPER LEVEL CLOUDS TO THE N OF THE ITCZ REGION. EXPECT THE COLD FRONT IN THE CENTRAL ATLC TO CONTINUE TO MOVE TO THE E OVER THE NEXT COUPLE OF DAYS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON