000 AGXX40 KNHC 151841 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM 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... AN EARLIER MORNING ASCAT PASS AND RECENT SHIP AND BUOY OBSERVATIONS SHOW 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 MOVES INTO THE NW GULF OVERNIGHT TONIGHT AND TRANSLATES E-NE BY WED MORNING. THIS FRONTAL TROUGH IS ASSOCIATED WITH A MIDDLE TO UPPER LEVEL SHORTWAVE LOW/TROUGH CURRENTLY OVER NORTH-CENTRAL MEXICO AND THE CENTRAL RIO GRANDE RIVER VALLEY WHICH IS EXPECTED TO PHASE WITH A NORTHERN STREAM TROUGH OVER THE MIDDLE MISSISSIPPI RIVER 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 N OF 12N BETWEEN 73W AND 82W...INCLUDING THE WINDWARD PASSAGE. THESE FRESH TRADES WILL DIMINISH BY THU AS A COLD FRONT MOVES THROUGH THE NORTHERN GULF OF MEXICO INTO THE SW NORTH ATLC...DISLODGING THE RIDGE AXIS CURRENTLY IN PLACE FROM JUST N OF BERMUDA NEAR 34N65W TO NORTHERN FLORIDA NEAR 29N81W. OVER THE TROPICAL N ATLC ZONE...AN AMPLIFYING DEEP-LAYER TROUGH IS IN PLACE WITH AXIS ALONG 31N54W TO A BASE NEAR 17N61W. ENERGY HAS SPLIT FROM THE COLD FRONT ALONG 28N BETWEEN 38W 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 THESE 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 BETWEEN 50W-60W THROUGH SAT. THEREFORE 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 NORTH ATLC. SW N ATLC S OF 31N W OF 55W... EARLIER SCATTEROMETER DATA AND SHIP/BUOY OBSERVATIONS SHOW FRESH TRADE WINDS ARE CONFINED PRIMARY S OF 26N IN THE AREA S OF THE RIDGE AXIS WHICH EXTENDS FROM JUST N OF BERMUDA TO THE NORTHERN FLORIDA PENINSULA. THE RIDGE AND TRADES WILL REMAIN IN PLACE UNTIL WED WHEN AN APPROACHING FRONT WILL MOVE 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 ECMWF TRENDS 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 INTO FRIDAY MORNING. THE FRONT DISSIPATES BY SAT...LEAVING HIGH PRES TO THE N OF THE AREA THAT WILL AGAIN ENHANCE THE TRADE WINDS. 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 HUFFMAN