000 AGXX40 KNHC 211832 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 135 PM EST TUE DEC 21 2010 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... ASIDE FROM A BACKDOOR-TYPE COLD FRONT THAT QUICKLY DROPS SE THROUGH THE EASTERN GULF WED NIGHT AND THU...CONDITIONS WILL REMAIN RELATIVELY UNCHANGED OVER THE GULF THROUGH FRI WITH SE RETURN FLOW OVER THE WESTERN GULF AND HIGH PRES DOMINATING THE FLOW REGIME OVER THE EASTERN GULF. A STRONG COLD FRONT IS EXPECTED TO MOVE OFF THE TX/LA COAST AROUND SUNSET FRI. THE MODELS CONTINUE TO SHOW SOME DISCREPANCIES WITH THE TIMING OF THE FRONT...WITH THE OLD 00Z ECMWF DEVELOPING A WAVE ALONG THE FRONT OVER THE NORTHERN GULF BY SAT. THE 12Z GFS ALSO DEVELOPS A WAVE...BUT IT DOES SO WELL N OF THE FORECAST AREA. THE 12Z CMC HAS A LOW TRACK BETWEEN THAT OF THE GFS AND ECMWF. STILL WAITING TO SEE THE 12Z UKMET. THE PROGS JUST RELEASED WERE BASED ON THE MORE PROGRESSIVE 12Z GFS SOLUTION..BUT THIS FORECAST MAY NEED TO BE REVISITED AS THE 12Z NOGAPS AND THE 00Z UKMET HOLD A WAVE ALONG THE FRONT IN THE GULF LIKE THE ECMWF. CARIBBEAN AND TROPICAL N ATLC... AN INCREASING PRES GRADIENT BETWEEN THE SOUTHWARD MOVING RIDGE AXIS OVER THE SW N ATLC AND LOWER PRES OVER SOUTH AMERICA WILL ACT TO EXPAND THE 20 KT NE WINDS OVER THE NORTHERN HALF OF THE CARIBBEAN TODAY THROUGH THU. WINDS SHOULD BE STRONGEST DOWNWIND OF THE MONA AND WINDWARD PASSAGES WITH SEAS BUILDING TO 8 OR 9 FT WITHIN IN THE N SWELL PENETRATING THE N FACING PASSAGES OF THE NE CARIBBEAN. THE LOW PRES SYSTEM CURRENTLY NEAR BARBADOS APPEARS TO BE MORE OF AN OPEN TROUGH IN THE ASCAT PASS FROM 1312 UTC AND WINDS ARE GENERALLY IN THE 10-15 KT RANGE NEAR THE SYSTEM WHICH IS FORECAST TO CONTINUE TO WEAKEN UNDER INCREASED S-SW SHEAR WITH THE MAIN IMPACT BEING CONVECTION TRACKING W WITH THE SYSTEM. SW N ATLC... THE ASCAT PASS FROM 1448 UTC SHOWS WINDS TO GALE FORCE OVER THE NE CORNER OF THE FORECAST ZONE. BUOY 41046 JUST N OF THE AREA NEAR 32N69.5W REPORTED 37 KT WINDS AND 24 FT SEAS AT 18Z WHILE BUOY 41049 JUST E OF THE AREA NEAR 27.5N63W REPORTED 25 KT WINDS AND 21 FT SEAS AT THE SAME TIME. GALE FORCE WINDS AND SEAS OVER 20 FT AREA EXPECTED TO MOVE E OF THE AREA WED WITH A SECOND COLD FRONT MOVING INTO N WATERS WED NIGHT INTO THU...WITH WINDS JUST BELOW GALE FORCE EXPECTED JUST TO ITS E. THE MODELS ARE IN REASONABLE AGREEMENT ON THIS SCENARIO. THE MODELS DIVERGE WITH THE STRONG COLD FRONT EXPECTED TO MOVE INTO NW WATERS SAT. AS EXPLAINED IN THE GULF OF MEXICO SECTION...THE 12Z GFS IS MORE PROGRESSIVE THAN THE 00Z ECMWF WHICH DEVELOPS A SURFACE WAVE IN THE GULF AND CARRIES IT NE ACROSS N FL AND JUST N OF THE ZONE BY EARLY SUN MORNING. BECAUSE IT DEVELOPS A RELATIVELY STRONG COASTAL LOW...THE ECMWF BRINGS WINDS TO GALE FORCE OVER NW WATERS SUN MORNING. THE MODELS APPEAR TO STILL BE SORTING OUT THE DETAILS ON THE FORECAST FOR THE WEEKEND WITH RESPECT TO THIS FRONT. FOR NOW...THE FORECAST IS BASED ON THE 12Z GFS SOLUTION...BUT THIS THINKING MAY BE CHANGED BASED ON TRENDS IN THE LATEST MODEL RUNS BY TOMORROW. WARNINGS.. ATLC... .GALE WARNING N OF 28N E OF 70W...AMZ080. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER