000 AGXX40 KNHC 310730 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 330 AM EDT WED AUG 31 2011 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLC...AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... RECENT AND CURRENT BUOY OBSERVATIONS SHOW E-SE WINDS OF 10-15 KT THROUGHOUT THE AREA...EXCEPT IN THE EASTERN GULF S OF 25N WHERE A TIGHTER PRES GRADIENT IS GENERATING E-SE WINDS OF 12-20 KT. GULF WHERE WINDS HAVE VEERED TO THE SE AT 10 KT AND OVER THE FAR SOUTHERN MIDDLE GULF ZONE WHERE WINDS ARE SE 10-15 KT. OBSERVED SEAS THROUGHOUT ARE IN THE 1-3 FT...WITH THE EXCEPTION OF THE EASTERN ZONE S OF 25N WHERE SEAS ARE 2-4 FT. THE PRELIMINARY 0600 UTC SURFACE ANALYSIS SHOWS A TROUGH OVER THE WESTERN SW GULF ALONG 95W S OF 23N...WHILE A TROPICAL WAVE IS JUST E OF THE YUCATAN PENINSULA. ELSEWHERE...A WEAK PRES PATTERN IS PRESENT. THE FORECAST FOR THE REST OF THE WEEK AND THROUGH WEEKEND STILL HAS AN UNCERTAINTY FACTOR TO IT. LATEST MODEL RUNS CONTINUE TO SUGGEST...AS IN PREVIOUS DAYS...THAT LOW PRES DEVELOPS OVER THE SW GULF ZONE WITHIN THE NEXT 3 DAYS. IT APPEARS THAT THE MAIN PLAYERS FOR THIS TO HAPPEN ARE BECOMING MORE READILY APPARENT WITH THE TROUGH ALONG 95W ALREADY THERE...AND THE WAVE COMING INTO THE AREA THU THROUGH FRI. IN ADDITION...WATER VAPOR IMAGERY SHOWS A NARROW UPPER LEVEL TROUGH THAT STRETCHES NE TO SW FROM THE SE U.S. TO FAR NE MEXICO...WITHIN AMPLE MOISTURE TO ITS SE. VORTICITY ASSOCIATED WITH THE TROPICAL WAVE SHOULD COMBINE WITH TROUGH ENERGY ALREADY PRESENT TO INDUCE A SURFACE LOW IN THE VICINITY OF THE WESTERN GULF THU AND THU NIGHT. MODEL DIFFERENCES ARE NOTED WITH RESPECT TO MAINLY THE TRACK OF THIS LOW FEATURE. MODELS...WITH THE EXCEPTION OF THE GFS AND REGIONAL NAM...KEEP THE LOW MEANDERING ON A MUCH FURTHER S TRACK OVER THE WESTERN PART OF THE GULF BEFORE TRACKING IT NORTHWARD SOME FRI THROUGH SUN. THE GFS IS MUCH FURTHER TO THE N DEVELOPING A LOW OVER THE SW GULF THU THROUGH FRI... ANOTHER ONE IN THE N CENTRAL GULF BY SAT. NOGAPS HINTS AT A SIMILAR SCENARIO...BUT IS LESS AGGRESSIVE WITH WINDS AND SEAS SEAS COMPARED WITH THE GFS. WILL LEAN WITH GENERAL MODEL CONSENSUS IN LOW DEVELOPING IN THE AREA OF THE WESTERN GULF OVER THE NEXT 2-3 DAYS..AND TAKING IT SLOWLY NORTHWARD. IN ANY EVENT...THE PRES GRADIENT SHOULD TIGHTEN NEAR THE LOW TO RESULT IN POSSIBLE E-SE WINDS OF 20-25 KT...AND SE-S 15-20 KT IN THE EASTERN PORTION OF THE SW GULF. THE TIGHT FETCH CREATED BY THE TIGHTENING GRADIENT SHOULD RESULT IN BUILDING SEAS AS HIGH AS PERHAPS 7 OR 8 FT BY SAT. LATEST NOAA WAVEWATCH GUIDANCE LOOKS REASONABLE WITH INITIAL SEA STATE VALUES...AND WILL BE USED FOR THROUGH EARLY THU. THEN AFTER THAT WILL MOSTLY ADJUST SEA HEIGHTS SUBSTANTIALLY UPWARDS ...SIMILAR TO THE ECMWF WAVE GUIDANCE TO ACCOUNT FOR THE BUILDING SEAS UNDER THE TIGHT PRES GRADIENT ASSOCIATED WITH THE LOW. SW ATLC S OF 31N W OF 55W... BOTH LATEST BUOY AND ASCAST DATA REVEAL RATHER LIGHT WIND AND SEAS CONDITIONS THROUGHOUT. WINDS ARE E-SE 10-15 KT E OF THE BAHAMAS...EXCEPT E-SE 10-15 KT S OF 24N...AND SE-S 10-15 KT ELSEWHERE. THE EXCEPTION IS OVER THE WATERS BETWEEN THE SE BAHAMAS AND HISPANIOLA WHERE A TIGHTER PRES GRADIENT THERE IS ACCOUNTING FOR NE-E WINDS OF 15-20 KT. SEAS ARE IN THE 2-4 FT N OF 27N E OF 76W...AND 2-3 FT N OF 27N W OF 76W. SEAS ELSEWHERE ARE 3-5 FT E OF THE BAHAMAS...AND 2-3 FT W OF BAHAMAS. SEAS E OF THE BAHAMAS ARE FORECAST TO SUBSIDE TO 2-3 FT...AND CONDITIONS THROUGHOUT SHOULD VARY VERY LITTLE THROUGH THE PERIOD. THE PRELIMINARY 0600 UTC ANALYSIS SHOWS A WEAK RIDGE STRETCHING FROM 27N65W TO S FLORIDA...AND THIS REMAINS THE MAIN FEATURE ACROSS THE AREA. THE RIDGE WILL LIFT NWD TODAY AND TONIGHT... THEN WEAKEN AND RETREAT EASTWARD WED AND THU AS A WEAK COLD FRONT ENTERS INTO THE NW PORTION. THE FRONT WILL MOVE SLOWLY E ACROSS THE NORTHERN WATERS WED THROUGH SAT WITH A WEAK PRES PATTERN SETTING UP OVER THE AREA. A NARROW SWATH OF 15-20 KT E WINDS WILL EXIST BETWEEN THE SE BAHAMAS THROUGH AT LEAST WED NIGHT. CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W... ASCAT DATA FROM 0200 UTC LAST NIGHT ALONG WITH RECENT AND CURRENT BUOY OBSERVATIONS REVEAL LIGHT E WINDS THROUGHOUT...EXCEPT IN THE CARIBBEAN PORTION FROM 11N-18N BETWEEN 68W-76W WHERE WINDS ARE NE-E 15-20 KT...AND OVER THE EASTERN PART OF THE NW CARIBBEAN WHERE WINDS ARE SE-S 15-20 KT. WINDS ARE NE-E 10 KT IN THE TROPICAL N ATLC ZONE. UPCOMING CHANGES TO AREA WINDS WILL BE SEEN AS AN EXPANSION OF THE 15-20 KT CARIBBEAN WINDS NORTHWESTWARD THROUGH MOST OF THU AS THE GRADIENT BETWEEN THE ATLC RIDGE AND LOWER PRES OVER THE SOUTHERN CARIBBEAN SEAS W OF 70W INCREASES. LATER ON THU AND INTO SAT THE GRADIENT WEAKENS WITH THE RIDGE N OF THE AREA RETREATING EASTWARD ALLOWING FOR THE E-SE WINDS TO DIMINISH TO MOSTLY 10-15 KT...EXCEPT IN THE FAR SOUTHERN SECTION OF THE EASTERN CARIBBEAN AND NEAR THE NE COAST OF HONDURAS WHERE WINDS SHOULD REMAIN AT 20 KT SPEEDS. EXPECT SEAS UP TO 9 FT IN THE SW CARIBBEAN N OF 12N BETWEEN 75W-80W AND NEAR THE COAST OF COLOMBIA THROUGH WED NIGHT BEFORE SUBSIDING TO 7 FT THU...AND TO 2-4 FT BY SAT. NEWLY UPGRADED TROPICAL STORM KATIA IN THE FAR EASTERN ATLANTIC IS FORECAST TO APPROACH TO THE TROPICAL N ATLC BY LATE FRI...AND TRACK NW ACROSS THE NORTHERN PORTION OF THE ZONE THROUGH SAT. PLEASE SEE THE LATEST INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADER MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS ON TROPICAL STORM KATIA. WARNINGS... GULF OF MEXICO... .NONE. CARIBBEAN... .NONE. TROPICAL N ATLC... .AMZ087...HURRICANE CONDITIONS EXPECTED N OF 15N E OF 60W SAT... SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER AGUIRRE