000 AGXX40 KNHC 211856 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 200 PM EST WED NOV 21 2012 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLC...AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... BROAD UPPER LEVEL RIDGE OVER WESTERN GULF RETURNS A MOIST AIR MASS W OF 92W WHILE DEEP TROUGH AXIS MAINTAINS DRY CONDITIONS E OF 92W. WEAK LEFTOVER SURFACE TROUGH EXITS EXTREME SW CORNER OF BAY OF CAMPECHE TONIGHT WITH ITS ASSOCIATED SCATTERED SHOWERS. ELSEWHERE... BROAD SURFACE HIGH PRES CENTER 1025 MB MOVING ACROSS SE STATES MAINTAINS A STEADY FLOW OF NE-E GENTLE TO MODERATE BREEZE THROUGH THU. W OF 90W...WINDS VEER SE IN ADVANCE OF COLD FRONT ENTERING NORTHERN COASTAL WATERS EARLY FRI. COLD FRONT REACH FROM FLORIDA BIG BEND TO BROWNSVILLE TEXAS LATE FRI WITH FRESH NE BREEZE AND SEAS 5-7 FT N OF FRONTAL BOUNDARY THROUGH SAT THEN DIMINISH / SUBSIDE EARLY SUN AS FRONT WEAKENS. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... LOW LEVEL CONVERGING WIND FLOW BETWEEN MODERATE EASTERLY TRADES AND FRESH N WINDS W OF 80W COMBINED WITH TROPICAL MOISTURE ADVECTED BY WEAK LOW PRES CENTER S OF COSTA RICA HAVE MIXED TO FORM SCATTERED MODERATE TO STRONG CONVECTION S OF 15N W OF 75W. A QUICK PASSING UPPER LEVEL SHORT WAVE HAS CONTRIBUTED MINOR UPPER LEVEL DIVERGENCE TO ENHANCE THAT CONVECTION TEMPORARILY. LOW PRES EXPECTED TO DRIFT W AS SHORT WAVE CONTINUE ITS NE PATH BY THU BREAKING THE ELEMENTS APART AND IMPROVING CONDITIONS IN SW CARIBBEAN AFTER FRI. ELSEWHERE IN CARIBBEAN...WEAK SURFACE TROUGH FROM PUERTO RICO TO WESTERN VENEZUELA HAS FLATTENED THE PRES GRADIENT PRODUCING LIGHT TO GENTLE BREEZE E OF 78W. SW N ATLC W OF 55W... COMPLEX DEEP LAYER CYCLONE JUST N OF SW N ATLC ZONE USHERS STRONG TO NEAR GALE N WINDS W OF 73W AS VERY STRONG COLD FRONT SWEEPS THROUGH BASIN REACHING FROM LOW PRES CENTER 1000 MB AT 29N71W TO 20N72W LATE THU AND E OF ZONE LATE FRI. GFS SOLUTIONS BRING GALE FORCE WIND GUSTS FOR SHORT PERIODS ALONG AND W OF FRONTAL BOUNDARY TONIGHT WITH SEAS AS HIGH AS 18 FT...BUT OTHER MODELS CUT SHY OF GALE FORCE. FORECAST FOLLOWS UKMET WHICH IS MORE CONSERVATIVE THAN GFS AND IN LINE WITH ENSEMBLE. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE GULF OF MEXICO... .NONE. CARIBBEAN SEA AND TROPICAL N ATLC... .NONE. SW N ATLANTIC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER WALLY BARNES