000 AGXX40 KNHC 261830 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 230 PM EDT WED SEP 26 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... A SURFACE TROUGH IS IN THE SW GULF FROM 23N95W TO 18N94W AS CAPTURED BY A RECENT WINDSAT SCATTEROMETER PASS. OTHERWISE... FAIRLY TRANQUIL CONDITIONS WILL PERSIST THROUGH FRI WITH LIGHT TO MODERATE ANTICYCLONIC WINDS ACROSS THE GULF AROUND A HIGH POSITIONED NE OF THE AREA. SEAS WILL BE MAINLY 2-3 FT...LOCALLY TO 4 FT. UNCERTAINTY REMAINS FOR THE UPCOMING WEEKEND WHEN SOME OF THE FORECAST MODELS SHOW REMNANT ENERGY FROM EASTERN PACIFIC TROPICAL CYCLONE MIRIAM PASSING OVER A RIDGE ALOFT OVER NE MEXICO AND MOVING IT INTO THE BACKSIDE OF AN AMPLIFYING EASTERN U.S. TROUGH...FORCING A SURFACE COLD FRONT OFF THE TEXAS COAST. THE 12Z GFS PUSHES THE FRONT THROUGH THE GULF MORE QUICKLY AND ALSO DOES NOT INDICATE MUCH OF A CLOSED LOW DEVELOPING ALONG THE FRONT. THE ECMWF HAS A SLOWER MIGRATION OF THE FRONT AND ALSO DEVELOPS A BETTER DEFINED LOW ALONG THE FRONT. WITH A MORE DEFINED LOW...THE ECMWF ALSO CARRIES 20-25 KT WINDS W OF THE LOW AND FRONT WHILE THE GFS SOLUTION INDICATES 10-15 KT WINDS BEHIND THE FRONT AT BEST. CONFIDENCE REMAINS LOW GIVEN THE CONTINUED DIFFERENCES OF THESE TWO SOLUTIONS. GIVEN THE LINGERING UNCERTAINTY A BLEND OF THE 12Z GFS AND 00Z ECMWF WAS USED FROM FRI ONWARD. SOUTHWEST NORTH ATLC S OF 31N W OF 55W... A SURFACE TROUGH...THE REMNANTS OF AN OLD STATIONARY FRONT... EXTENDS FROM NEAR 31N70W TO ACROSS THE NORTHERN BAHAMAS TO THE STRAITS OF FLORIDA. THIS FEATURE IS FORECAST TO DISSIPATE BY TONIGHT. A RECENT WINDSAT SCATTEROMETER PASS INDICATED MAINLY LIGHT TO MODERATE WINDS ON EITHER SIDE OF THIS TROUGH ACROSS THE SW N ATLC REGION. BROAD HIGH PRES WILL BE NE OF BERMUDA WITH A WEAK RIDGE EXTENDING ACROSS THE WATERS FOLLOWING DISSIPATION OF THE TROUGH. THE 12Z GFS HAS BACKED OFF A BIT REGARDING SOUTHERLY WINDS ALONG 70W AS IT CARRIES A MID TO UPPER LEVEL TROUGH EASTWARD FROM FL INTO THE CENTRAL ATLC AND MIXES THE SOUTHERLY JET AHEAD OF THE TROUGH TO THE SURFACE. PREVIOUS MODEL RUNS HAD WINDS TO 25 KT ALTHOUGH THE 06Z AND 12Z RUNS NOW SHOW 15-20 KT AT BEST AHEAD OF THIS FEATURE. THESE RUNS ARE NOW IN BETTER AGREEMENT WITH THE REMAINING GLOBAL MODELS WHICH ALSO SHOW WINDS TO A FRESH BREEZE AT MOST. AN ASSOCIATED SURFACE COLD FRONT IS FORECAST TO MOVE INTO THE FAR NW PORTION SUN MORNING...VERY SLOWLY REACHING FROM 31N77W TO NEAR JUPITER FLORIDA BY MON MORNING. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... A TROPICAL WAVE IN THE CENTRAL CARIBBEAN ALONG 73W REMAINS SOMEWHAT DIFFICULT TO FIND AS IT INTERACTS WITH AN UPPER TROUGH STRETCHED FROM THE NE CARIBBEAN TO THE COAST OF COLOMBIA. THIS INTERACTION CONTINUES TO CAUSE CONVECTION TO FLARE NEAR THE WAVE AXIS WHERE UPPER LEVEL DIFFLUENCE IS ENHANCING VERTICAL LIFT. THE CONVECTION SHOULD BEGIN TO WANE TONIGHT AS THE WAVE MOVES W OF THE UPPER TROUGH AXIS...INTO A REGION OF MORE CONFLUENT FLOW ALOFT. A RECENT WINDSAT SCATTEROMETER PASS SHOWED AN AREA OF FRESH TO STRONG TRADES W OF THE WAVE AXIS WHILE NDBC BUOY 42058 NEAR 15N75W IS REPORTING 8 FT SEAS. THESE WINDS ARE FORECAST TO DIMINISH BELOW ADVISORY CRITERIA LATER THIS AFTERNOON AS THE PRES GRADIENT WEAKENS. OVER THE WEEKEND...HIGH PRES IS EXPECTED TO BUILD INTO THE CENTRAL ATLC FORCING A TIGHTER PRES GRADIENT OVER THE CARIBBEAN E OF 75W. EXPECT MODERATE TO FRESH E-SE WINDS TO DEVELOP OVER MAINLY THE CENTRAL CARIBBEAN SUN AND MON...WITH LIGHT TO MODERATE WINDS ELSEWHERE. 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 LEWITSKY