000 AGXX40 KNHC 160659 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 200 AM EST WED NOV 16 2011 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... THE 0336 UTC ASCAT PASS SHOWS FRESH TO STRONG RETURN FLOW IN THE CENTRAL PORTION OF THE GULF AHEAD OF THE WEAK FRONTAL TROUGH MAKING ITS WAY THROUGH THE NW GULF. THIS AREA OF RETURN FLOW IS EXPECTED TO SHIFT NE AND DISSIPATE TODAY. THE FRONTAL TROUGH IS ASSOCIATED WITH UPPER ENERGY THAT IS CURRENTLY PHASING WITH A NORTHERN STREAM TROUGH OVER THE MISSISSIPPI VALLEY. A REINFORCING COLD FRONT ASSOCIATED WITH THE NORTHERN STREAM TROUGH WILL PLOW INTO THE N GULF OVERNIGHT TONIGHT. THE MODELS ARE IN GOOD AGREEMENT WITH THE FRONTAL TIMING CARRYING THE WEAKENING FRONT THROUGH S FLORIDA BY FRI NIGHT. THE GFS CONTINUES TO CARRY A STRONGER FRONT THAN THE ECMWF...WITH THE 00Z GFS SHOWING 20 KT WINDS ACROSS THE ENTIRE BAY OF CAMPECHE OVERNIGHT THU NIGHT AND ALLOWS STRONG NE WINDS TO REMAIN BEHIND THE FRONT INTO FRI WHILE THE ECMWF IS WEAKER IN CAMPECHE AND HAS FRESH WINDS IN THE NE GULF. THE UKMET SHOWS MORE AGREEMENT WITH THE WEAKER ECMWF. THEREFORE...WILL CONTINUE THE CURRENT REASONING OF GOING SLIGHTLY WEAKER THAN THE GFS TOWARD A MODEL COMPROMISE. CARIBBEAN SEA AND TROPICAL N ATLC... HIGH PRES N OF THE AREA CONTINUES TO CREATE A TIGHT ENOUGH PRES GRADIENT ACROSS THE CARIBBEAN TO SUPPORT FRESH NE TRADE WINDS PRIMARILY OVER THE CENTRAL CARIBBEAN ACCORDING TO THE ASCAT PASS FROM 0152 UTC. THESE FRESH TRADES WILL DIMINISH BY THU AS A COLD FRONT MOVES THROUGH THE NORTHERN GULF OF MEXICO INTO THE SW N ATLC...DISLODGING THE RIDGE AXIS CURRENTLY IN PLACE FROM JUST N OF BERMUDA TO CENTRAL FLORIDA. FRESH NE WINDS WERE ALSO CAPTURED BY THE 0152 UTC ASCAT PASS IN THE FAR NE CARIBBEAN AND NW TROPICAL N ATLC WHERE THE PRES GRADIENT IS TIGHT BETWEEN THE AFOREMENTIONED RIDGE AND LOW LEVEL TROUGHING OVER THE TROPICAL N ATLC FROM 22N57W TO 14N61W. THIS LOW LEVEL TROUGH IS THE REFLECTION OF BROAD TROUGHING ALOFT THAT ENCOMPASSES BOTH ENERGY THAT HAS SPLIT FROM AN OLD FRONTAL BOUNDARY TO THE NE AND ENERGY THAT HAS SPILLED INTO THE THE TROUGH FROM THE NW. WHILE IT IS DIFFICULT FOR THE MODELS TO GET A GOOD HANDLE ON THIS FINE-SCALE FEATURES...THEY HAVE COME INTO AGREEMENT...ASIDE FROM THE NOGAPS...ON DEVELOPING AN UPPER CYCLONE JUST N OF THE TROPICAL N ATLC TONIGHT THAT WILL REMAIN STATIONARY THROUGH SUN. A BLEND OF THE GFS AND ECMWF WAS USED FOR THE FORECAST WHICH KEEPS THE STRONGEST WINDS AND HIGHEST SEAS PRIMARILY IN THE NW CORNER OF THE ZONE WHERE THE PRES GRADIENT WILL REMAIN GREATEST BETWEEN THE SURFACE REFLECTION OF THE TROUGH ALOFT AND RIDGING OVER THE SW N ATLC. SW N ATLC S OF 31N W OF 55W... THE 0154 UTC ASCAT PASS AND SHIP/BUOY OBSERVATIONS SHOW FRESH TRADE WINDS ARE CONFINED PRIMARY S OF 23N E OF 78W IN THE AREA S OF THE RIDGE AXIS WHICH EXTENDS FROM JUST N OF BERMUDA TO CAPE CANAVERAL FLORIDA. AN APPROACHING FRONT HAS BEGUN TO SHOVE THE RIDGE SOUTHWARD...WITH THE PRES GRADIENT INCREASING OVER NW WATERS BETWEEN THE RIDGE AND THE FRONT. THE SAME ASCAT PASS SHOWS SOME FRESH SOUTHERLY FLOW OFF THE N FLORIDA COAST. WINDS WILL PICK UP MORE TONIGHT AS THE FRONT APPROACHES. THE RIDGE WILL RETREAT EAST OF THE ZONE BY FRI AHEAD OF THE COLD FRONT. AS EXPLAINED IN THE GULF OF MEXICO SECTION...THE MODELS HAVE COME INTO BETTER AGREEMENT ON THE TIMING OF THE FRONT AND NOW CARRY THE WEAKENING BOUNDARY THROUGH S FLORIDA BY FRI NIGHT. THE MODELS ARE NOT IN AS GOOD AGREEMENT WITH STRENGTH OF THE WINDS BEHIND THE FRONT...WITH THE GFS INCREASING WINDS TO 25 KT BEHIND THE FRONT BY THU NIGHT WHILE THE ECMWF WAITS UNTIL SUNRISE FRI. THE UKMET TIMING IS BETWEEN THE TWO MODELS. LIKE IN THE GULF OF MEXICO...A COMPROMISE BETWEEN THE STRONGER GFS AND WEAKER ECMWF IS PREFERRED WITH THE FRONT. WINDS WILL REMAIN FRESH TO STRONG OVER MUCH OF THE SW N ATLC OFFSHORE ZONE...SAVE NW WATERS...OVER THE WEEKEND AS HIGH PRES BEHIND THE FRONT BUTTS UP AGAINST THE PERSISTENT TROUGHING JUST E OF THE AREA AND N OF THE TROPICAL N ATLC ZONE. WARNINGS... GULF OF MEXICO... .NONE. .CARIBBEAN SEA AND TROPICAL N ATLC... .NONE. .SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER