000 AGXX40 KNHC 210740 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 340 AM EDT SUN JUL 21 2013 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W...AND THE SW N ATLANTIC INCLUDING THE BAHAMAS. ...GULF OF MEXICO... MODEL PREFERENCE: GFS/ECMWF/OFFICIAL BLEND WITH GOOD CONFIDENCE. NWPS FOR WAVE HEIGHTS. AN UPPER CYCLONE OVER THE LOWER MISSISSIPPI VALLEY CONTINUES TO WEAKEN THIS MORNING. THIS HAD SUPPORTED LINES OF CONVECTION ACROSS MUCH OF THE NW AND N CENTRAL GULF THE PREVIOUS EVENING...BUT THIS HAS LARGELY DIMINISHED. THE MAIN INFLUENCE OVER THE WEATHER IN THE GULF THROUGH MID WEEK WILL BE A RIDGE EXTENDING FROM THE WESTERN ATLC ACROSS THE FLORIDA PENINSULA ALONG 27N TO THE TEXAS COAST. THIS WILL RESULT IN GENERALLY LIGHT TO MODERATE FLOW ACROSS THE GULF THROUGH EARLY IN THE WEEK WITH SEAS REMAINING 2 TO 4 FT OVERALL. THE EXCEPTION WILL BE THE ROUTINE INCREASE IN WINDS OFF THE WEST COAST OF THE YUCATAN PENINSULA. TO VARYING DEGREES GLOBAL MODELS ARE ADVERTISING WEAK LOW PRES MOVING THROUGH THE SOUTHERN PLAINS BY MIDWEEK. THIS WILL ENHANCE SOUTHERLY RETURN FLOW OVER THE NW GULF SLIGHTLY. DEEP LAYER MOISTURE IS STARTING TO SHUNT NORTHWARD WITH THE BUILDING RIDGE. THIS WILL ALLOW THE OFTEN PROLIFIC THUNDERSTORM ACTIVITY OVER THE PAST FEW DAYS TO DIMINISH FOR THE MOST PART ACROSS THE GULF. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC... MODEL PREFERENCE: GFS/ECMWF/OFFICIAL BLEND WITH GOOD CONFIDENCE. NWPS FOR WAVE HEIGHTS OVER CARIBBEAN BASIN. THE MAIN CONCERN THIS MORNING RELATES TO WINDS TO GALE FORCE OVER THE S CENTRAL CARIBBEAN NEAR THE COAST OF COLOMBIA. EARLIER SCATTEROMETER DATA SHOWED A LARGE AREA OF 30 TO 35 KT TRADE WINDS BETWEEN ROUGHLY 72W AND 76W...IMPACTING VESSEL TRAFFIC BETWEEN THE WINDWARD PASSAGE AND THE PANAMA CANAL. THIS WAS CONFIRMED BY SHIP A8SF9 WHICH INDICATED 35 KT WINDS NEAR 12N 75.5W AROUND 06 UTC. THE GALE FORCE WINDS ARE THE RESULT OF A TIGHT GRADIENT BETWEEN HIGH PRES N OF THE AREA OVER THE WESTERN ATLC...IN THE WAKE OF TROPICAL WAVE THAT RECENTLY MOVED INTO CENTRAL AMERICA. SEAS AT BUOY 42056 WERE 11 FT AT 06 UTC...WITH PEAK WINDS TO 29 KT. SEAS ARE LIKELY HIGHER FARTHER SOUTH IN THE AREA OF MAXIMUM WINDS. NWPS OUTPUT WAS AS HIGH AS 17 FT...WELL ABOVE THE 13 FT FROM THE WNA10. GIVEN 30 KT PLUS TRADE WIND FLOW WITH A FETCH AS LONG AS 150 NM AND A DURATION OF MORE THAN A DAY...MAXIMUM SEAS OF LEAST 15 FT SEEM PLAUSIBLE. OFFICIAL FORECAST LEANS TOWARD NWPS WITH SOME LOCAL MODIFICATION IN THE AREA OF MAXIMUM SEAS WHERE THE GALES ARE OCCURRING. FARTHER TO THE NW...REPORTS FROM THE BAY ISLANDS IN THE GULF OF HONDURAS SHOWED E WINDS TO 20 KT. WINDS TO 25 KT OVER THE WATERS SEEM LIKELY...ALTHOUGH THIS IS MOST LIKELY ONLY THROUGH THE OVERNIGHT AND EARLY MORNING HOURS. ELSEWHERE MODERATE TO FRESH TRADES DOMINATE ACROSS THE BASIN AND TROPICAL N ATLC WATERS W OF 55W. A TROPICAL WAVE APPROACHING 55W WILL NEAR THE EASTERN CARIBBEAN THIS EVENING...THEN MOVE THROUGH THE CENTRAL CARIBBEAN THROUGH LATE TUE. THIS WILL RESULT IN A DIMINISHING TREND FOR WINDS OVER THE S CENTRAL GULF. GALES ARE EXPECTED TO END BY EARLY AFTERNOON...THE CONTINUE TO DIMINISH TO BELOW 30 KT BY TONIGHT...AND BELOW 25 KT BY LATE MON AHEAD OF THE APPROACHING WAVE. SEAS WILL SUBSIDE ACCORDINGLY...BELOW 12 FT BY LATE TODAY...AND BELOW 8 FT TUE. THE RIDGE TO THE NORTH WILL WEAKEN OVER THE NEXT COUPLE OF DAYS. AS A RESULT...THE WINDS DO NOT APPRECIABLY INCREASE THROUGH MID WEEK IN THE WAKE OF THE TROPICAL WAVE AS HAS HAPPENED OVER THE PAST SEVERAL DAYS WITH PREVIOUS TROPICAL WAVES. LOOKING WAY AHEAD TO THE END OF THE WEEK...THE OPERATIONAL GFS CONTINUES TO ADVERTISE A STRONG TROPICAL SYSTEM MOVING ACROSS THE ATLC. WHILE CONSISTENT...THE GFS REMAINS A STARK OUTLIER WITH EVERY OTHER MODEL INCLUDING THE ENSEMBLE GFS AND THE USUALLY BULLISH CANADIAN. THIS SEEMS TO BE A CONVECTIVE FEEDBACK ISSUE...AND THE OFFICIAL FORECAST FOR THE END OF THE WEEK FAVORS THE ECMWF SHOWING AN OPEN WAVE WITH WINDS TO 25 KT. NWPS DOES NOT GO THAT FAR IN TIME...SO FORECAST SEAS ARE HEAVILY MODIFIED FROM THE WAY OVERDONE WW3 WITH MAXIMUM SEAS TO 9 FT IN THE AREA OF STRONG WINDS. ...SW N ATLANTIC W OF 55W INCLUDING THE BAHAMAS... MODEL PREFERENCE: GFS/ECMWF/OFFICIAL BLEND WITH GOOD CONFIDENCE. A 1023 MB HIGH PRES AREA IS CENTERED NEAR 29N67W...WITH A RIDGE EXTENDING E TO W ALONG ROUGHLY 28/29N. S OF 22N...RECENT SCATTEROMETER PASSES AND BUOY OBSERVATIONS SHOW MODERATE E FLOW...AND UP TO 20 KT OFF THE NORTH COAST OF HAITI AND TOWARD THE ENTRANCE TO THE WINDWARD PASSAGE. GENERALLY LIGHT TO MODERATE FLOW IS NOTED ELSEWHERE...WITH NEAR CALM WINDS NEAR THE CENTER OF THE HIGH. THE CONVERGENCE OF SE WINDS AROUND THE RIDGE WITH SW WINDS OFF NE FLORIDA IS INTERACTING WITH SLIGHTLY UNSTABLE BOUNDARY LAYER CONDITIONS OVER THE GULF STREAM TO SUPPORT A LINE OF THUNDERSTORMS THIS MORNING FROM OFF WEST PALM BEACH FLORIDA TO NEAR 31N79W. A TROPICAL WAVE MOVING THROUGH THE CENTRAL CARIBBEAN BY TUE...WILL ALLOW WINDS TO INCREASE SLIGHTLY S OF 22N. THE RIDGE IS EXPECTED TO WEAKEN AND SHIFT NE MON INTO TUE AHEAD OF A WEAK COLD FRONT MOVING ACROSS THE SOUTHEAST UNITED STATES. WHILE THE FRONT STALLS BEFORE REACHING THE COAST...THE TIGHTER GRADIENT WILL RESULT IN ENHANCED SW WINDS TO 20 KT N OF 29N W OF 70W BY MID WEEK. $$ .WARNINGS...ANY CHANGES IMPACTING COASTAL NWS OFFICES WILL BE COORDINATED THROUGH AWIPS 12 PLANET CHAT OR BY TELEPHONE: .GULF OF MEXICO... GMZ011...NONE. GMZ013...NONE. GMZ015...NONE. GMZ017...NONE. GMZ019...NONE. GMZ021...NONE. GMZ023...NONE. GMZ025...NONE. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... AMZ011...NONE. AMZ013...NONE. AMZ015...NONE. AMZ017...NONE. AMZ019...NONE. AMZ021...NONE. AMZ023...NONE. AMZ025...NONE. AMZ027...NONE. AMZ029...NONE. AMZ031...GALE WARNING EARLY TODAY. AMZ033...NONE. AMZ035...NONE. AMZ037...NONE. AMZ039...NONE. .SW N ATLANTIC INCLUDING THE BAHAMAS... AMZ111...NONE. AMZ113...NONE. AMZ115...NONE. AMZ117...NONE. AMZ119...NONE. AMZ121...NONE. AMZ123...NONE. AMZ125...NONE. AMZ127...NONE. *FOR DETAILED ZONE DESCRIPTIONS PLEASE VISIT: HTTP://WWW.NHC.NOAA.GOV/ABOUTTAFBPROD.SHTML#OWF NOTE: GRIDDED MARINE FORECASTS ARE AVAILABLE IN THE NATIONAL DIGITAL FORECAST DATABASE (NDFD) AT: HTTP://WWW.NHC.NOAA.GOV/MARINE/GRIDS.PHP FOR ADDITIONAL INFORMATION PLEASE VISIT: HTTP://WWW.HURRICANES.GOV/MARINE $$ .FORECASTER CHRISTENSEN. NATIONAL HURRICANE CENTER.