000 AGXX40 KNHC 010730 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 330 AM EDT SEP 01 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 2-3 FT RANGE IN THE WESTERN GULF...AND 3-6 FT OVER THE REMAINDER OF THE GULF...WITH THE HIGHEST S OF 26N. THE PRELIMINARY 0600 UTC SURFACE ANALYSIS SHOWS A TROPICAL WAVE EXTENDING FROM 27N89W TO 18N92W MOVING W AT 10 KT. ELSEWHERE...A WEAK RIDGE IS NE OF THE AREA. THE FORECAST FOR THE GULF REMAINS WITH UNCERTAINTY WITH RESPECT TO PENDING DEVELOPMENT OF A LOW PRES FEATURE THAT HAS BEEN ADVERTISED BY THE MODELS DURING THE PAST SEVERAL DAYS. LATEST MODEL RUNS CONTINUE TO SUGGEST THAT LOW PRES DEVELOPS OVER THE AREA PERHAPS IN THE WESTERN OR MIDDLE GULF ZONES OVER THE NEXT 48 HOURS. VORTICITY ASSOCIATED WITH THE TROPICAL WAVE IN COMBINATION WITH BROAD TROUGHINESS OVER THE EASTERN AND MIDDLE PORTIONS SHOULD COMBINE TO DEVELOP THE LOW. WATER VAPOR IMAGERY SHOWS A LARGE ANTICYCLONE ACROSS THE GULF WITH AMPLE MOISTURE ALOFT. MODELS TO SOME EXTENT ARE IN MORE AGREEMENT...AS COMPARED TO THE PREVIOUS RUNS...THAT THE LOW STARTS TO EVOLVE FROM THE WAVE AS IT MOVES THROUGH THE MIDDLE GULF ZONE TODAY...AND IN A NW DIRECTION DIRECTION TOWARDS THE GENERAL VICINITY OF THE NW GULF THROUGH FRI NIGHT...THEN DIFFERENCES COME INTO THE PLAY WITH HOW THE LOW TRACKS DURING THE WEEKEND AND INTO MON. THE GFS STILL LIKES TO TAKE THE LOW TOWARDS THE LOUISIANA COAST SAT...AND THEN EASTWARD ALONG THEN EASTWARD SUN AND MON. THE ECMWF IS SIMILAR TO THE UKMET IN TAKING THE LOW TO THE NW GULF FRI...AND KEEP IT STATIONARY THROUGH MON. THE NOGAPS TAKES IT INLAND SW LOUISIANA LATE FRI NIGHT INTO SAT. THE REGIONAL NAM IS SIMILAR WITH THAT TRACK. ALL MODELS...WITH THE EXCEPTION OF THE NOGAPS...DEEPEN THE LOW QUITE DRASTICALLY. THIS IS ANOTHER ISSUE TO DEAL WITH IN THE FORECAST OF THIS FUTURE SYSTEM...BECAUSE THE INTENSIFICATION OF THE LOW HINGES ON THE WINDS ALOFT WITH RESPECT TO SHEAR AFTER DAY 2 WHICH MAY BE A FACTOR. FOR NOW...WILL MAINTAIN STATUS QUO AND FORECAST BROAD LOW PRES TO MEANDER OVER THE MIDDLE AND EASTERN PORTION OF THE WESTERN GULF THROUGH TONIGHT...THEN SLOWLY MOVE THE LOW NW THROUGH SAT. IN ANY EVENT...IMPLICATIONS TO WINDS AND SEAS WILL BE SEEN WHEN THE PRES GRADIENT TIGHTENS NEAR AND TO THE N AND NE OF THE LOW TO RESULT IN E-SE AND SE-S WINDS OF 15-20 KT OVER MUCH OF THE MIDDLE AND WESTERN ZONES...WITH WINDS INCREASING TO E-SE 20-25 KT IN THE NORTHERN PORTION OF THE MIDDLE GULF FRI THROUGH SUN. THE TIGHT PRES GRADIENT SHOULD BUILD SEAS AS HIGH AS 9 FT IN THE FAR NORTHERN MIDDLE GULF SAT THROUGH MON. 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. THE NAH BUILDS SEAS VERY LARGE TO 14 FT SAT THROUGH MON IN THE NE GULF. WILL DISCOUNT THOSE VALUES FOR NOW...AND WAIT TO SEE HOW SCENARIO DEVELOPS BEFORE FORECASTING THOSE HIGH VALUES. SW ATLC S OF 31N W OF 55W... BOTH LATEST BUOY AND ASCAT 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 SLIGHTER TIGHTER PRES GRADIENT THERE IS ALLOWING FOR NE-E WINDS OF 15 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 2-4 FT E OF THE BAHAMAS...AND 2-3 FT W OF BAHAMAS. CONDITIONS SHOULD VARY LITTLE THROUGH THE PERIOD. THE PRELIMINARY 0600 UTC ANALYSIS SHOWS A WEAK RIDGE STRETCHING FROM 25N65W TO 21N70W. THE RIDGE WILL RETREAT EASTWARD THROUGH FRI AS A WEAK FRONTAL TROUGH MOVES ACROSS THE NORTHERN WATERS. THE TROUGH WILL MOVE SLOWLY E ACROSS THE NORTHERN WATERS THROUGH SUN BEFORE BECOME DIFFUSE WITH A WEAK PRES PATTERN SETTING UP OVER THE AREA. HURRICANE KATIA CURRENTLY ABOUT 1165 MILES E OF THE LEEWARD ISLANDS S FORECAST TO APPROACH THE FAR SE PORTION SE PORTION LATE SUN. AS A RESULT...EXPECT WINDS TO BECOME NE AND INCREASE TO 15 TO 20 KT...WITH BUILDING SEAS IN THE FAR SE PORTION LATE ON SUN. CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W... ASCAT DATA FROM NEAR 03206 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 WHERE 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 S OF 16N BETWEEN 68W-75W...HOWEVER WINDS ARE FORECAST TO DIMINISH TO E-SE 15-20 KT THIS MORNING 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 FOR FRI THROUGH MON... HURRICANE KATIA IN THE ATLANTIC IS FORECAST TO APPROACH THE TROPICAL N ATLC FRI...AND TRACK NORTHWESTWARD 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... GULF OF MEXICO... .NONE. CARIBBEAN... .NONE. TROPICAL N ATLC... .AMZ087...HURRICANE WARNING N OF 16N E OF 61W FRI INTO EARLY MON... SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER AGUIRRE