000 AGXX40 KNHC 121834 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 235 PM EDT MON MAY 11 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... WEAK COLD AIR ADVECTION WEST OF A 1016 MB SURFACE LOW N OF LAKE OKEECHOBEE HAS FORCED THE COLD FRONT OVER THE NORTHERN GULF TO SURGE SOUTHWARD OVER THE EASTERN GULF...NOW EXTENDING FROM NEAR FORT MYERS FLORIDA TO MOBILE ALABAMA. LATEST VISIBLE SATELLITE IMAGERY AND RADAR TRENDS DEPICT THIS FEATURE WELL...AND THE QUIKSCAT PASS AROUND 12/1130 UTC SHOWS N TO NE WINDS OF 10 TO 15 KT NE OF THE FRONT. THIS LOW IS LIKELY BEING DRIVEN BY WEAK MID/UPPER-LEVEL LIFT ASSOCIATED WITH A WEAK MID/UPPER-LEVEL TROUGH TRAILING SW FROM THE W ATLC. HOWEVER...DEEP SUPPORT IS NOT PARTICULARLY ABUNDANT IN THIS REGION...AND THE LOW WILL LIKELY BECOME ENTRAINED WITHIN A SURFACE RIDGE OVER THE REGION AS THE FRONT BECOMES RE-ESTABLISHED TO THE NORTH OVER THE GULF COAST STATES LATER TODAY. THUS...AFTER A TEMPORARY WIND SHIFT TO THE N TO NE ACROSS THE E GULF TODAY...WINDS WILL VEER TO NE TO E AT THE SW PERIPHERY OF THE RIDGE TONIGHT ACROSS THE EASTERN GULF. OTHERWISE...E TO SE WINDS OF 10 TO 15 KT PREVAIL ACROSS MUCH OF THE GULF BASED ON SHIP OBSERVATIONS. AS A RESULT...WIND WAVES OF 3 TO 5 FT ARE OCCURRING ACROSS MUCH OF THE SOUTHWESTERN HALF OF THE GULF. THESE WINDS ARE DRIVEN BY THE PERSISTENT SURFACE RIDGE ACROSS THE N GULF THAT EXTENDS WESTWARD FROM A SURFACE HIGH OVER THE CENTRAL ATLC. THIS RIDGE HAS BEEN SHUNTED SOUTHWARD A BIT OVER THE E GULF AS A RESULT OF THE PREVIOUSLY DISCUSSED FRONTAL PASSAGE. A 1017 MB SURFACE HIGH OVER THE CENTRAL WATERS LIES AT THE WESTERN TIP OF THIS RIDGE AND IS MAINTAINING LIGHT AND VARIABLE WINDS OVER THE CENTRAL GULF...WHERE SEAS ARE LESS THAN 2 FT. 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 W GULF AND 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 THE WEEKEND 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 LATE WEEK INTO THE WEEKEND. CARIBBEAN... SURFACE HIGH PRESSURE N OF THE CARIBBEAN SEA IS MAINTAINING FRESH NE TO E TRADE WINDS ACROSS THE CARIBBEAN. THE QUIKSCAT PASS AROUND 12/1130 UTC INDICATES NE TO E WINDS OF 10 TO 15 KT ACROSS THE NW CARIBBEAN...WITH NE TO E WINDS OF 20 TO 25 KT ACROSS THE SW CARIBBEAN...HIGHEST NEAR THE COAST OF COLOMBIA. ACROSS THE E CARIBBEAN...E WINDS OF 15 TO 20 KT PREVAIL. WAVEWATCH GUIDANCE INDICATES SEAS TO 9 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...WITH MAXIMUM SEAS SUBSIDING NEAR THE COAST OF COLOMBIA TO 8 FT. FOR THIS WEEKEND...DEVELOPING LOW PRESSURE OVER THE CENTRAL ATLC WILL WEAKEN THE PRESSURE GRADIENT ACROSS THE CARIBBEAN...RESULTING IN TRADE WINDS DECREASING ACROSS THE ENTIRE CARIBBEAN. ATLANTIC S OF 31N W OF 55W... QUIKSCAT PASSES AROUND 12/0800 UTC AND 12/0945 UTC SHOW A WELL-DEFINED E-W SUBTROPICAL RIDGE EXTENDING FROM A 1026 MB SUBTROPICAL HIGH OVER THE CENTRAL ATLC NEAR 31N44W TO THE SE CONUS COAST. 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 APPROACHING PUERTO RICO. THE SURFACE HIGH IS FORECAST TO MOVE EASTWARD AS ITS ASSOCIATED UPPER LEVEL RIDGE TRANSLATES EASTWARD IN RESPONSE TO AN UPPER TROUGH CURRENTLY BEING MOVING EASTWARD OVER THE W ATLC. HOWEVER...A PERSISTENT SURFACE RIDGE ALONG 28N/29N WILL MAINTAIN THESE TRADE WINDS THROUGH MID-WEEK. AT THE SAME TIME...MID/UPPER-LEVEL LIFT CONTINUES TO DEEPEN A 1016 MB LOW OVER THE SW NORTH ATLC NEAR 30N79W. THIS LOW IS ALONG A COLD FRONT THAT EXTENDS FROM NEAR ORLANDO FLORIDA TO 31N76W. 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 8 FT IN THE N SEMICIRCLE OF THE LOW. THE ECMWF AND GFS ARE HANDLING THIS LOW QUITE WELL...WHILE THE NAM IS PLACING THIS LOW TOO FAR WESTWARD ALONG THE COAST AND NOT INCREASING THE ASSOCIATED WINDS ENOUGH. 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 9 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 WILL LIKELY BUILD TO 8 TO 13 FT BY SAT. ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FORECASTER COHEN. TROPICAL PREDICTION CENTER.