000 AGXX40 KNHC 150705 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EST TUE NOV 15 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 0356 UTC ASCAT PASS SHOWS FRESH TO STRONG RETURN FLOW IN THE GULF W OF 94W. THIS AREA OF RETURN FLOW IS EXPECTED TO SHIFT NE AS A WEAK FRONTAL TROUGH PUSHES INTO THE NW GULF OVERNIGHT TONIGHT. THIS FRONTAL TROUGH IS ASSOCIATED WITH THE UPPER LOW CURRENTLY OVER N CENTRAL MEXICO AND EXPECTED TO PHASE WITH A NORTHERN STREAM TROUGH OVER THE MISSISSIPPI VALLEY BY TONIGHT. THE MODELS HAVE COME INTO MUCH BETTER AGREEMENT ON THIS FORECAST...WITH THE MOST SIGNIFICANT DIFFERENCES COMING WITH THE FORECAST FOR THE REINFORCING COLD FRONT ASSOCIATED WITH THE NORTHERN STREAM TROUGH. THE 00Z ECMWF IS FASTER THAN THE GFS TO CARRY THE BOUNDARY SOUTHWARD THROUGH FL AND THE EASTERN GULF THU/FRI. A BLEND OF THESE TWO MODELS WILL BE USED FOR THE FORECAST WHICH BRINGS FRESH TO STRONG NE WINDS TO THE NORTHERN HALF OF THE GULF THU/FRI BEHIND THE REINFORCING FRONT. 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 S OF 19N ACCORDING TO THE ASCAT PASS FROM 0214 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 N FLORIDA. OVER THE TROPICAL N ATLC ZONE...AN AMPLIFYING DEEP-LAYER TROUGH IS IN PLACE. ENERGY HAS SPLIT FROM THE COLD FRONT ALONG 28N BETWEEN 35W AND 50W INTO THE EASTERN EDGE OF THIS TROUGH WHILE ENERGY IS ALSO SPILLING INTO THE WESTERN EDGE OF THIS TROUGH FROM THE N. WHILE IT IS DIFFICULT FOR THE MODELS TO GET A GOOD HANDLE ON THIS FINE-SCALE FEATURES...THE 00Z ECMWF AND GFS ARE IN REASONABLE AGREEMENT WITH THE FORECAST ALOFT WHICH KEEPS A WEAK UPPER CYCLONE OVER THE TROPICAL N ATLC TONIGHT THROUGH SAT. 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 BE GREATEST BETWEEN THE SURFACE REFLECTION OF THIS TROUGH ALOFT AND THE RIDGING OVER THE SW N ATLC. SW N ATLC S OF 31N W OF 55W... THE 0216 UTC ASCAT PASS AND SHIP/BUOY OBSERVATIONS SHOW FRESH TRADE WINDS ARE CONFINED PRIMARY S OF 27N IN THE AREA S OF THE RIDGE AXIS WHICH EXTENDS FROM JUST N OF BERMUDA TO N FLORIDA. THE RIDGE AND TRADES WILL REMAIN IN PLACE UNTIL WED WHEN AN APPROACHING FRONT WILL SHOVE THE RIDGE SOUTHWARD...WITH THE PRES GRADIENT INCREASING OVER NW WATERS BETWEEN THE RIDGE AND THE FRONT AND OVER SE WATERS BETWEEN THE RIDGE AND THE AMPLIFYING DEEP LAYER TROUGH OVER THE TROPICAL N ATLC ZONE. THE RIDGE WILL RETREAT EAST OF THE ZONE BY FRI AHEAD OF THE COLD FRONT. AS EXPLAINED IN THE GULF OF MEXICO SECTION...THE 00Z ECMWF IS SLIGHTLY FASTER THAN THE GFS WITH THE FRONT AS IT PASSES THROUGH FLORIDA THU/FRI. BOTH MODELS SHOW STRONG NE WINDS BEHIND THE FRONT OVER NW WATERS BEGINNING OVERNIGHT THU NIGHT. THE FRONT DISSIPATES BY SAT...LEAVING HIGH PRES TO THE N OF THE AREA THAT WILL AGAIN ENHANCE THE TRADE WINDS. A BLEND OF THE GFS AND ECMWF IS PREFERRED FOR THE FORECAST. 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