000 AGXX40 KNHC 310853 AAA MIMATS MARINE WEATHER DISCUSSION...UPDATED NWS NATIONAL HURRICANE CENTER MIAMI FL 450 AM EDT WED AUG 31 2011 UPDATED TROPICAL N ATLC AND WARNINGS SECTION FOR FORECAST AND WARNING CONDITIONS REGARDING TROPICAL STORM KATIA 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...WITH 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 00 UTC 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 THU...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 WEAKEN AND RETREAT THROUGH THU AS A WEAK FRONTAL TROUGH MOVES INTO THE NW PORTION. THE TROUGH WILL MOVE SLOWLY E ACROSS THE NORTHERN WATERS THROUGH SUN WITH A WEAK PRES PATTERN SETTING UP OVER THE AREA. HURRICANE KATIA CURRENTLY IN THE FAR EASTERN ATLC IS FORECAST TO APPROACH THE FAR SE PORTION SE PORTION LATE SUN. AS A RESULT...EXPECT WINDS TO BECOME NE AND INCREASE TO 15 KT WITH BUILDING SEAS IN THE FAR SE PORTION LATE ON SUN. CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W...UPDATED ASCAT DATA FROM NEAR 0200 UTC LAST NIGHT ALONG WITH RECENT AND CURRENT BUOY OBSERVATIONS SHOW E-SE 10-15 KT THROUGHOUT IN THE CARIBBEAN AND NE-E 10-15 KT WINDS IN THE TROPICAL ATLC ZONE. THE EXCEPTIONS ARE NOTED IN THE CARIBBEAN S OF 16N BETWEEN 68W AND 75W WHERE NE-E 20-25 KT ARE PRESENT...AND ELSEWHERE N OF 12N BETWEEN 65W AND 75W WHERE E WINDS OF 15-20 KT ARE PRESENT...AND ALSO IN THE NW CARIBBEAN ZONE BETWEEN 75W AND 85W WHEER E-SE WINDS OF 15-20 KT EXIST. E-SE WINDS OF 15-20 KT WILL SPREAD NORTHWESTWARD ACROSS THE NW CARIBBEAN THROUGH FRI AS THE GRADIENT BETWEEN THE ATLC RIDGE AND LOWER PRES OVER THE SOUTHERN CARIBBEAN SEA W OF 70W INCREASES. BEGINNING ON FRI 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 WHERE WINDS SHOULD BE NE-E 15-20 KT...AND NEAR THE NE COAST OF HONDURAS WHERE E-SE WINDS SHOULD BE SEEN AT 15-20 KT SPEEDS. EXPECT SEAS UP TO 9 FT IN THE SW CARIBBEAN N OF S OF 16N BETWEEN 68W-75W...HOWEVER WINDS ARE FORECAST TO DIMINISH TO E-SE 15-20 KT THU NIGHT AND SEAS FORECAST TO SUBSIDE TO 4-6 FT FRI. CONCERNING MAJOR CHANGES WITH REGARDS TO WINDS AND SEAS OF THE NORTHERN TROPICAL N ATLC ZONE IN THE LONG TERM PERIODS...TROPICAL STORM KATIA IN THE FAR EASTERN ATLANTIC IS FORECAST TO INTENSIFY INTO A HURRICANE TODAY...THEN APPROACH THE TROPICAL N ATLC FRI ...AND TRACK NORTWESTEARD ACROSS ITS FAR NORTHERN WATERS LATE FRI NIGHT THROUGH SUN. WINDS AND SEAS WILL DRASTICALLY INCREASE AS TROPICAL FORCE WINDS MOVE IN FIRST...THEN FOLLOWED BY HURRICANE FORCE WINDS. 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...UPDATED GULF OF MEXICO... .NONE. CARIBBEAN... .NONE. TROPICAL N ATLC... .AMZ087...HURRICANE CONDITIONS EXPECTED N OF 16N E OF 61W FRI THROUGH SUN... SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER AGUIRRE