000 AGXX40 KNHC 131824 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 224 PM EDT WED MAY 13 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... RETURN FLOW CONTINUES ACROSS THE GULF AROUND A SURFACE RIDGE N OF THE GULF EXTENDING WESTWARD FROM A SURFACE HIGH OVER THE CENTRAL ATLC. E TO SE WINDS OF 10 TO 15 KT PREVAIL ACROSS MUCH OF EASTERN HALF OF THE GULF BASED ON SHIP OBSERVATIONS AND THE QUIKSCAT PASS AROUND 13/1100 UTC. ACROSS THE WESTERN HALF OF THE GULF...PRESSURE FALLS OVER THE SOUTHERN PLAINS ARE BACKING SURFACE WINDS TO MORE OF A SE TO S DIRECTION...WITH WIND SPEEDS OF 15 TO 20 KT BASED ON SEVERAL SHIP OBSERVATIONS. AS A RESULT...WIND WAVES OF 4 TO 7 FT ARE OCCURRING ACROSS MUCH OF THE WESTERN HALF OF THE GULF...WITH SEAS OF 1 TO 3 FT ACROSS THE EASTERN HALF. THIS GENERAL PATTEN IS FORECAST TO CONTINUE THROUGH LATE WEEK...THOUGH WINDS WILL BECOME MORE EASTERLY ACROSS THE GULF BY THE WEEKEND AS A SURFACE RIDGE BECOMES ESTABLISHED FURTHER N. BY LATE WEEK INTO THE WEEKEND...WINDS WILL BE STRONGEST OVER THE FLORIDA STRAITS...WHERE WIND SPEEDS WILL REACH THE 20-25 KT RANGE THU-SAT. NE TO E WINDS OF 20 TO 25 KT WILL ALSO OCCUR AROUND THE COAST OF YUCATAN THROUGH FRIDAY DURING THE EVENING HOURS...DRIVEN BY VARIATIONS IN THE LOCAL TOPOGRAPHY OVER YUCATAN. SEAS WILL BUILD TO 4-6 FT ACROSS MUCH OF THE GULF BY FRIDAY. GLOBAL MODEL GUIDANCE INDICATES AN OVERALL WEAKNESS IN THE SURFACE PRESSURE GRADIENT ACROSS THE GULF THIS WEEKEND IN RESPONSE TO THE APPROACH OF A SOUTHERN PLAINS COLD FRONT. AS A RESULT...WIND SPEEDS AND SEA HEIGHTS WILL DECREASE THIS WEEKEND. WINDS WILL ALSO SHIFT TO THE NE TO E DURING THIS TIME. BY LATE IN THE WEEKEND INTO EARLY NEXT WEEK...RECENT OPERATIONAL RUNS OF THE GFS...GFS ENSEMBLES...NOGAPS...AND THE CMC ALL INDICATE THE DEVELOPMENT OF A SURFACE LOW IN THE VICINITY OF THE FLORIDA PANHANDLE. AMONG THE GUIDANCE SUITE...A LARGE SPECTRUM EXISTS IN THE STRENGTH...POSITION...AND TRACK OF THIS LOW...AS WELL AS ITS ASSOCIATED WIND FIELD. IT APPEARS THAT THIS LOW WILL LIKELY FORM NEAR A SOUTHWESTWARD TRAILING MID-LEVEL TROUGH ASSOCIATED WITH THE AFOREMENTIONED FRONT EARLY MONDAY. IN THE ABSENCE OF ANY REMARKABLE SURFACE FEATURES OR DEEP LAYER FORCING...THE OPERATIONAL GFS LIKELY SUGGESTS CYCLOGENESIS TOO FAST OVER THE E GULF ON SUNDAY. IT IS MORE LIKELY THAT THE LOW WILL DEVELOP FARTHER E OVER THE FLORIDA PENINSULA OR SW NORTH ATLC ON MONDAY...WHEN THE TRAILING MID-LEVEL TROUGH AMPLIFIES OVER THE BROAD AREA OF LOW PRESSURE ACROSS THE GULF AND FLORIDA. THIS SOLUTION IS MOST IN LINE WITH THE CMC...WHICH INDICATES A HYBRID SUBTROPICAL/EXTRATROPICAL LOW OVER THE WESTERN ATLC AS OPPOSED TO THE GULF OF MEXICO. FORECAST CONFIDENCE IS CURRENTLY RATHER LOW IN THE PARTICULARS OF THIS SCENARIO...AND WILL CONTINUE TO BE MONITORED. CARIBBEAN... SURFACE HIGH PRESSURE N OF THE CARIBBEAN SEA IS MAINTAINING FRESH NE TO E TRADE WINDS ACROSS THE CARIBBEAN. THE QUIKSCAT PASS AROUND 13/1100 UTC INDICATES NE TO E WINDS OF 10 TO 15 KT ACROSS THE NW CARIBBEAN...WITH NE TO E WINDS OF 15 TO 20 KT ACROSS THE SW CARIBBEAN...EXCEPT UP TO 25 KT NEAR THE COAST OF COLOMBIA. ACROSS THE E CARIBBEAN...E WINDS OF 15 TO 20 KT PREVAIL. WAVEWATCH GUIDANCE INDICATES SEAS TO 8 FT NEAR THE COAST OF COLOMBIA...WITH SEAS OF 4 TO 7 FT ACROSS MUCH OF THE S CARIBBEAN. THIS PATTERN IS FORECAST TO PERSIST THROUGH MID-WEEK UNTIL A SUBTROPICAL SURFACE HIGH OVER THE CENTRAL ATLC MOVES EASTWARD. THE STRONGEST WINDS WILL CORRESPONDINGLY SHIFT TOWARD THE E CARIBBEAN BY LATE WEEK. FOR THIS WEEKEND...DEVELOPING LOW PRESSURE OVER THE CENTRAL ATLC AND THE BROAD LOW PRESSURE OVER THE GULF DISCUSSED ABOVE WILL WEAKEN THE PRESSURE GRADIENT ACROSS THE CARIBBEAN...RESULTING IN TRADE WINDS DECREASING ACROSS THE ENTIRE CARIBBEAN BY SATURDAY...WITH WINDS GENERALLY LESS THAN 20 KT AND SEAS LESS THAN 6 FT BY SUNDAY AREAWIDE. ATLANTIC S OF 31N W OF 55W... THE QUIKSCAT PASS AROUND 13/0920 UTC SHOWS A WELL-DEFINED E-W SUBTROPICAL RIDGE EXTENDING FROM A 1029 MB SUBTROPICAL HIGH OVER THE CENTRAL ATLC NEAR 33N36W TO THE SW N ATLC. E TRADE WINDS AT THE SOUTHERN PERIPHERY OF THIS SURFACE RIDGE ARE GENERALLY IN THE 15-20 KT RANGE ACROSS THE BAHAMAS...GREATER AND LESSER ANTILLES...AND THE TROPICAL N ATLC...WHERE SHIP OBSERVATIONS SHOW SEAS OF 6-7 FT. THE STRONGEST OF THESE WINDS ARE FOUND AROUND A SURFACE TROUGH OVER HISPANIOLA. THE SURFACE HIGH IS FORECAST TO MOVE EASTWARD AS ITS ASSOCIATED UPPER LEVEL RIDGE TRANSLATES EASTWARD IN RESPONSE TO AN UPPER TROUGH CURRENTLY MOVING EASTWARD OVER THE W ATLC. AT THE SAME TIME...MID/UPPER-LEVEL LIFT CONTINUES TO MAINTAIN A 1020 MB LOW OVER THE SW NORTH ATLC NEAR 30N76W. THIS LOW IS ALONG A FRONT THAT EXTENDS FROM THE SE CONUS COAST ACROSS THE SW N ATLC ALONG 30N. DURING THE NEXT DAY...THE FRONT IS FORECAST TO MAKE LITTLE SOUTHWARD PROGRESS S OF 28N AS THE UPPER TROUGH TAKES A WEST-TO-EAST TRACK WITH LIMITED DIGGING SOUTHWARD. NE TO E WINDS OF 20 TO 25 KT ARE PRESENT NW OF THE FRONT N OF 30N...WITH SEAS UP TO 6 FT. HOWEVER...DURING THE NEXT DAY...THE SURFACE LOW WILL CONTINUE TO TRACK NORTHEASTWARD TOWARD HIGHER SURFACE PRESSURE NEAR THE RIDGE...RESULTING IN AN INCREASE IN WINDS IN THE NORTHERN SEMICIRCLE OF THE LOW TO 20 TO 25 KT. THE STRONGEST OF THESE WINDS WILL INCREASE SEAS TO 9 FT IN THE N SEMICIRCLE OF THE LOW. SURFACE HIGH PRESSURE N OF THE FRONT OVER THE W ATLC WILL INCREASE E TRADE WINDS TO 20 TO 25 KT W OF THE BAHAMAS... PARTICULARLY OVER THE FLORIDA STRAITS FOR THU INTO SAT...WHERE SEAS WILL BUILD TO 10 FT. ALSO...BY LATE WEEK...AN UPPER LEVEL JET STREAK DIVING SOUTHEASTWARD OVER THE NORTHERN ATLC WILL CUT THE AFOREMENTIONED TROUGH OFF FROM THE PRIMARY UPPER FLOW WITH A DEVELOPING SURFACE LOW ALONG THE FRONT OVER THE CENTRAL ATLC. THIS WILL FORCE THE FRONT TO STRENGTHEN AND MOVE SOUTHWARD INTO THE N TROPICAL ATLC BY THIS WEEKEND. THE STRONGEST WINDS...IN THE 20-30 KT RANGE...WILL BE FOUND WITHIN IN THE W SEMICIRCLE OF THE OCCLUDED LOW LATE SAT...MAINLY N OF 26N BETWEEN 55W-65W. THESE WINDS WILL BUILD SEAS IN THIS REGION TO 8 TO 13 FT BY SAT. WHILE THE OPERATIONAL GFS HAS COME DOWN SOMEWHAT WITH REGARD TO THE STRENGTH OF THE LOW AND ASSOCIATED WIND FIELD...THE UKMET...NOGAPS...AND ECMWF ARE INDICATING A DEEPER LOW WITH A STRONGER WIND FIELD OVER THE WESTERN SEMICIRCLE OF THE LOW. CONSENSUS SUGGESTS THE STRONGER LOW SOLUTION IS PREFERRED...WITH MAX WINDS TO 30 KT IN THE WESTERN SEMICIRCLE OF THE LOW. THE THREAT FOR GALES WILL BE MITIGATED BY THE LIKELY ABSENCE OF DEEP CONVECTION AND INDUCED PRESSURE FALLS NEAR THE LOW...WHERE SEA SURFACE TEMPERATURE ANOMALIES ARE NEAR NEUTRAL COMPARED TO SEASONAL AVERAGES. ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FORECASTER COHEN. TROPICAL PREDICTION CENTER.