000 AGXX40 KNHC 161844 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 245 PM EDT SAT MAY 16 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 AREA AROUND THE WRN PERIPHERY OF A SURFACE RIDGE THAT EXTENDS WESTWARD FROM A SURFACE HIGH OVER THE WRN ATLC. E TO SE WINDS OF 10 TO 15 KT PREVAIL ACROSS JUST ABOUT THE ENTIRE GULF AS NOTED BY BOTH BUOY OBSERVATIONS AND A QUIKSCAT PASS FROM NEAR 1200 UTC THIS MORNING...EXCEPT FOR THE FAR SE WATERS NEAR THE STRAITS OF FL WHERE SE 20 KT WINDS ARE BEING OBSERVED. RELATED WIND WAVES BEING REPORTED ARE IN THE 3-5 FT RANGE ACROSS THE MAJORITY OF THE GULF...EXCEPT IN THE SOUTHERN PORTION OF THE ERN GULF WHERE SEAS ARE 4-6 FT AND TO 8 FT NEAR THE STRAITS OF FL. THIS PATTEN OF WINDS AND SEAS IS FORECAST TO CONTINUE THROUGH TONIGHT OVER ALL ZONE EXCEPT FOR THE NW GULF AS A COLD FRONT FRONT MAKES HEADWAY INTO THAT SECTION. WINDS OVER THE FAR SE GULF NEAR THE STRAITS OF FL DIMINISH TO 10-15 KT ON SUN. NE-E WINDS OF 20-25 KT WILL ALSO OCCUR AROUND THE COAST OF THE YUCATAN PENINSULA DURING THE EVENING HOURS THROUGH SUN NIGHT...DRIVEN BY VARIATIONS IN THE LOCAL TOPOGRAPHY OVER YUCATAN WITH WIND FLOW AROUND THE LAND MASS. LATEST GLOBAL MODEL GUIDANCE INDICATES AN OVERALL WEAKNESS IN THE SURFACE PRESSURE GRADIENT ACROSS THE GULF THROUGH SUN NIGHT IN RESPONSE TO THE APPROACH OF A SOUTHERN PLAINS COLD FRONT AND POSSIBLE LOW/TROUGH EMERGING FROM NEAR NW CUBA NWD TOWARDS THE VICINITY OF CUBA AND THE NE YUCATAN PENINSULA AS NCEP DETERMINISTIC MODELS AND EVEN THE REGIONAL NAM SUGGEST. AS A RESULT...WIND SPEEDS AND SEA HEIGHTS ARE FORECAST TO INCREASE BEHIND THE FRONT BEGINNING SUN AFTERNOON. BY LATE MON WINDS WILL SHIFT TO N-NE AND INCREASE OVERSPREADING JUST ABOUT THE ENTIRE GULF. PRESENT MODEL INDICATIONS ARE THAT THE LOW WILL LIKELY FORM NEAR A SWWD TRAILING MID-LEVEL TROUGH ASSOCIATED WITH THE AFOREMENTIONED FRONT BEGINNING SOMETIME MON. CONSENSUS TRACK PROJECTIONS BY THE MODELS SHOW THE LOW TRACKING IN A N OR NE DIRECTION. IT IS STILL TOO EARLY TO PINPOINT JUST HOW CLOSE TO THE GULF THIS FEATURE WILL COME. IT STILL APPEARS OF THAT THE LOW WILL BE ON THE WEAK SIDE WITH POSSIBLE INCLINATIONS THAT IT MAY BE OF A HYBRID TYPE...PROBABLY MORE ONCE IT GETS CLOSER TO THE WRN ATLC AS OPPOSED TO THE GULF OF MEXICO. FORECAST CONFIDENCE IS SLIGHTLY BETTER IN REGARDS TO THE EVOLUTION OF A LOW FEATURE ...BUT REMAINS VERY LOW WITH RESPECT TO EXACT INTENSITY AND TRACK GUIDANCE. WILL CLOSELY FOLLOW FUTURE MODEL RUNS AND UPPER AIR DATA TO GET A BETTER GRIP ON THIS UPCOMING SCENARIO. CARIBBEAN SEA... SURFACE HIGH PRESSURE N OF THE CARIBBEAN SEA IS MAINTAINING MOSTLY LIGHT TO MODERATE ELY TRADES ACROSS THIS AREA. A QUIKSCAT PASS FROM 1118 UTC THIS MORNING SHOWED NE-E WINDS OF 10-15 KT ACROSS THE NW CARIBBEAN...WITH NE TO E WINDS OF 15-20 KT S OF 18NE OF 77W AS ALSO NOTED IN BUOY OBSERVATIONS AND BY A COUPLE OF SHIP OBSERVATIONS. WAVEWATCH GUIDANCE FROM 1200 UTC THIS MORNING INDICATES NO SEAS OF 8 FT OR GREATER WHICH COINCIDES WELL WITH CURRENT OBSERVED SEA STATE. EARLIER TODAY THERE WAS A SMALL POCKET OF SEAS TO 8 FT NEAR THE COLOMBIAN COAST...BUT HAVE SINCE SUBSIDED TO AROUND 6-7 FT. OVER THE REMAINDER OF THE SEA...SEA STATE VALUES ARE 5-7 FT OVER THE ERN PORTION S OF 16N AND 3-5 FT 3-5 FT ELSEWHERE EXCEPT THE NW PORTION WHERE VALUES ARE MUCH LOWER...IN THE 1-2 FT RANGE. THIS PATTERN IS FORECAST TO PERSIST THROUGH EARLY MON. ATLC HIGH PRES THEN SHIFTS EWD AS WEAK LOW PRES FORMS IN THE VICINITY OF WRN CUBA AND THE YUCATAN CHANNEL. WITH THE LOW FORMING THE PRES GRADIENT WILL WEAKEN ACROSS THE WRN AND MOST OF THE CENTRAL CARIBBEAN...RESULTING IN LIGHT TRADES ACROSS THE ENTIRE SEA INTO THU...WITH WINDS GENERALLY IN THE 10-15 KT RANGE WITH MAYBE A FEW INSTANCES OF E 15-20 KT WINDS OVER THE S CENTRAL PORTION. WINDS OVER THE NW PORTION WILL SHIFT CYCLONICALLY AT 10-15 KT AROUND THE LOW AND ASSOCIATED TRAILING TROUGH INTO THE NE YUCATAN PENINSULA...BUT MAY BE SIGNIFICANTLY HIGHER IF THE LOW DEEPENS MORE THAN PREDICTED BY THE MODELS...AND ALSO IN AND NEAR ASSOCIATED CONVECTIVE ACTIVITY THAT FORMS IN RELATION TO THE LOW. SEA STATE IS EXPECTED TO REACH NO MORE THAN 6 FT BY SUNDAY AREA WIDE AND TO 5 FT BY TUE AND THROUGH THU. SEAS WILL REMAIN MUCH LOWER...ABOUT 1-2 FT NEAR THE HONDURAN COAST AND 2-3 FT N OF OF THERE OVER THE REMAINDER OF THE NW CARIBBEAN TUE THROUGH THU...BUT MAY KICK UP TO HIGHER VALUES DUE TO CONVECTION RELATED TO THE LOW. SW N ATLC AND TROPICAL N ATLC... SURFACE ANALYSIS FROM THIS MORNING AND EARLY AFTERNOON REVEALED A WELL-DEFINED NE-SW RIDGE OVER THE FAR NRN WATERS OF THE SW N ATLC. E TRADE WINDS AT THE SOUTHERN PERIPHERY OF THIS SURFACE RIDGE ARE GENERALLY IN THE 15-20 KT RANGE WITH A SWATH OF E-SE WINDS OF 20-25 KT S OF 25N W OF 73W...WITH SEAS IN THE 6-8 FT RANGE DUE TO THE PRES GRADIENT RESULTING FROM THE RIDGE AND LOWER PRES OVER THE NW CARIBBEAN SEA. THE SURFACE HIGH IS FORECAST TO MOVE EWD AS ITS ASSOCIATED UPPER LEVEL RIDGE TRANSLATES EWD IN RESPONSE TO AN UPPER TROUGH MOVING INTO THE FAR WRN PORTION OF THE AREA. THE WEAK THAT FORMS NEAR WRN CUBA MENTIONED ABOVE BEGINS TO PULL NWD IN RESPONSE TO A COLD FRONT DROPS INTO THE FAR NW WATERS MON AND BECOMES STATIONARY THROUGH WED...THEN LOSES ITS IDENTITY INTO THU. A TIGHT GRADIENT BETWEEN THE LOW AND FRONT WILL LEAD TO INCREASING ONSHORE WINDS OF 20-25 KT N OF 26N W OF ABOUT 76W BY WED WITH SEAS BUILDING 8-10 FT. ELSEWHERE WINDS WILL GENERALLY BE NE-E 15-20 KT EXCEPT OVER THE FAR W PORTION S OF THE LOW WHERE WINDS WILL BE LIGHTER ABOUT 10-15 KT SW-S IN DIRECTION...AND SEAS WILL BE IN LOWER RANGES. A WEAKENING COLD FRONT HAS JUST ENTERED THE FAR NRN WATERS OF THE TROPICAL N ATLC. THE FRONT WILL PRESS SWD AS IT DISSIPATES THROUGH EARLY NEXT WEEK. NE-E WINDS OF 15-20 KT ARE PRESENT N OF THE FRONT WITH SEAS TO 8 FT IN N SWELL...HOWEVER THESE CONDITIONS WILL DIMINISH THROUGH MON. ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FORECASTER AGUIRRE. TROPICAL PREDICTION CENTER.