000 AGXX40 KNHC 181944 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 345 PM EDT WED MAR 18 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... A MERIDIONAL SURFACE TROUGH LIES ALONG 87W IN THE EASTERN GULF OF MEXICO. SCATTERED SHOWERS AND TSTMS CAN BE FOUND PRIMARILY E OF THE TROUGH...WITH THE HEAVIEST CONCENTRATION N OF 25N. ACCORDING TO THE ASCAT PASS AT 1456 UTC...WINDS ON THE EASTERN EDGE OF THE TROUGH NEAR 26N ARE IN THE 20 TO 25 KT RANGE. BUOY 42003 LIES IN THE REGION OF TSTM ACTIVITY AND HAS BEEN REPORTING SUSTAINED WINDS IN THE 20 TO 30 KT RANGE SINCE 1200 UTC THIS MORNING. SATELLITE IMAGERY REVEALS THE PRESENCE OF A MID LEVEL LOW HERE...AND THE MODELS HAVE A GOOD HANDLE ON THIS FEATURE. THE SURFACE TROUGH IS EXPECTED TO SLOWLY SHIFT SW AND GRADUALLY DISSIPATE OVER THE SW GULF OVERNIGHT FRI NIGHT AS A RESULT OF THE RIDGING N OF THE MID LEVEL LOW BEING FORCED SOUTHWARD AS A DEEP LAYER TROUGH PASSES INTO THE GULF COASTAL STATES. THE ASSOCIATED COLD FRONT IS EXPECTED TO REACH THE NORTHERN GULF OF MEXICO OVERNIGHT THU NIGHT. STRONG HIGH PRESSURE WILL MOVE IN BEHIND IT AND WINDS SHOULD PICK UP FRI THROUGH THE WEEKEND OVER THE GULF. BY MON...THE NEXT DEEP LAYER TROUGH SHOULD MOVE INTO THE PLAINS...ENHANCING SOUTHERLY RETURN FLOW IN THE WESTERN GULF. CARIBBEAN... ACCORDING TO THE 1458 ASCAT PASS... WINDS HAVE CALMED CONSIDERABLY OVER THE CARIBBEAN WITH THE HIGHEST WINDS...TO 25 KT...CONTAINED OFF THE COLOMBIAN COAST. THIS FLOW WILL CONTINUE TO DIMINISH TODAY AS HIGH PRES WELL NE OF THE CARIBBEAN WEAKENS AND SHIFTS FURTHER EAST AHEAD OF A DEEP LAYER TROUGH MOVING THROUGH THE WESTERN ATLC. HIGH PRES CURRENTLY MOVING OFF THE MID ATLC COAST WILL MOVE EASTWARD PASSING N OF BERMUDA THU NIGHT...MAINTAINING MODERATE TO FRESH TRADE WINDS OVER THE EASTERN CARIBBEAN THROUGH THE WEEKEND. A SECOND MID/UPPER TROUGH PUSHES THROUGH THE EASTERN U.S. OVERNIGHT THU NIGHT...FOLLOWED BY STRONG SURFACE HIGH PRES BUILDING INTO THE GULF OF MEXICO/MID ATLC. THIS WILL INCREASE THE PRESSURE GRADIENT OVER THE CARIBBEAN AND INCREASE WINDS ONCE AGAIN OVER 20 KT OVER MUCH OF THE WESTERN CARIBBEAN OVER THE WEEKEND AND SPREADING INTO THE EASTERN CARIBBEAN MON. ATLANTIC S OF 31N W OF 55W... A COLD FRONT EXTENDS FROM A DEEPENING 1001 MB SURFACE LOW N OF THE AREA 31N56W TO 25N65W AND ALONG 65W INTO THE UPPER FL KEYS. THE ASCAT PASS FROM 1314 UTC SHOWS SOUTHERLY WINDS AHEAD OF THE FRONT REACHING JUST BELOW GALE FORCE OVER HIGH SEAS FORECAST WATERS. THIS COLD FRONT HAS SHIFTED HIGH PRESSURE EASTWARD AWAY FROM OFFSHORE FORECAST WATERS IN THE TROPICAL ATLC...DIMINISHING TRADE WINDS BELOW 20 KT. THROUGH THU...THE SURFACE LOW MOVES FURTHER EAST...AS HIGH PRES BUILDS BEHIND IT OFF THE EASTERN SEABOARD. FRESH TO STRONG NORTH WINDS DIMINISH OVER THE WATERS BETWEEN N FLORIDA AND BERMUDA...BUT THE NORTHERLY SWELL CONTINUES TO PUSH INTO THE AREA. MOST OF THE 15 TO 20 FT SWELL MISSES THE ISLANDS TO THE EAST AND WILL STAY MAINLY N OF 25N E OF 70W...LEAVING SWELL TO 8 FT ENVELOPING THE AREA. LOOKING AHEAD TO THE WEEKEND...THE NEXT MAJOR LONG WAVE TROUGH PUSHES OFF THE EASTERN U.S. OVERNIGHT THU NIGHT WITH A STRONG SW JET ALOFT AHEAD OF THE TROUGH. DIVERGENT FLOW ALOFT ON THE RIGHT REAR OF THE JET WILL SUPPORT DEVELOPMENT OF A WEAK SURFACE TROUGH JUST EAST OF THE BAHAMAS. AS THE UPPER TROUGH AMPLIFIES NORTH OF THE AREA...THE NEXT COLD FRONT MOVES OFF THE N FLORIDA COAST THU NIGHT. MODEL GUIDANCE SUGGESTS THE TROUGH MORPHING INTO A WEAK SURFACE LOW ALONG THE FRONTAL BOUNDARY AND LIFTING OUT TOWARD BERMUDA...BUT THEY DIFFER ON THE TIMING...WITH THE CONSENSUS MOVING THE LOW NORTHWARD TO BERMUDA LATE FRI NIGHT. THE TRAILING TROUGH EXTENDS FROM THE LOW PRES NEAR BERMUDA TO THE SOUTHERN BAHAMAS BY FRI NIGHT...AND FROM 31N60W TO NEAR THE MONA PASSAGE BY SUN. THE DEVELOPMENT OF THE LOW ALONG THE FRONT WILL TIGHTEN THE PRESSURE GRADIENT BETWEEN THE LOW AND HIGH PRES BUILDING BEHIND THE FRONT OVER THE EASTERN U.S. THIS IN TURN WILL RESULT IN A BROAD AREA OF STRONG NE WINDS...PERHAPS AS HIGH AS 30 KT...BEHIND THE FRONT BY LATE SAT. ATLANTIC... NONE. CARIBBEAN... NONE. GULF OF MEXICO... NONE. FORECASTER SCHAUER CLARK. TROPICAL PREDICTION CENTER.