000 AGXX40 KNHC 200831 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 300 AM EST TUE NOV 20 2012 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... LATEST AND RECENT BUOY AND OIL RIG PLATFORM OBSERVATIONS SHOW N-NE 15 KT WINDS E OF ABOUT 95W...EXCEPT IN THE MIDDLE AND E GULF PORTION S OF 25N WHERE THE ASCAT PASS FROM 0242 UTC LAST NIGHT REVEALED NE 20 KT WINDS. LIGHTER WINDS ARE OVER THE REMAINDER OF THE GULF...WITH NE-E WINDS OF 5-10 KT IN THE FAR NW PORTION AND N-NE 10 KT IN THE FAR NE PORTION. THE PRELIMINARY 6 UTC SYNOPTIC SCALE ANALYSIS DEPICTS A HIGH PRES RIDGE THAT STRETCHES FROM VERY STRONG HIGH PRES OVER NEW ENGLAND SW TO THE WESTERN AND N CENTRAL GULF. A WEAK SURFACE TROUGH MOVING W 15-20 KT EXTENDS FROM 25N92W SE TO ACROSS THE NORTHERN YUCATAN PENINSULA. THE PRES DIFFERENCE BETWEEN BOTH THE TROUGH AND LOWER PRES OVER WESTERN ATLC IS RESULTING IN THE NE 20 KT WINDS IN THE SRN SECTIONS OF THE MIDDLE AND E GULF. THE BUOY OBSERVATIONS ARE REPORTING SEA HEIGHTS OF 3-4 FT... EXCEPT FOR A SMALL POCKET OF HIGHER SEAS OF 4-6 FT WITH THE NE 15-20 KT WINDS...AND LOWER SEAS OF 2 FT N OF 28N. SATELLITE IMAGERY SHOWS SCATTERED TO BROKEN LOW LEVEL CLOUDS ASSOCIATED WITH THE AFOREMENTIONED TROUGH MOVING W WITH POSSIBLE ISOLATED SHOWERS OVER SRN MIDDLE GULF WATERS S OF 25N BETWEEN 87W-94W. A LARGE AREA OF OVERCAST LOW CLOUDS WITH EMBEDDED LIGHT RAIN AND DRIZZLE IS SPREADING WSW OVER THE FAR E GULF TO THE E OF 85W. WATER VAPOR SATELLITE IMAGERY DEPICTS BROAD RIDGING BUILDING IN OVER THE AREA. UPPER LEVEL MOISTURE IN THE FORM OF SCATTERED THIN CLOUDS IS STREAMING EASTWARD FROM THE EASTERN PACIFIC OVER THE...AND SPREADING EASTWARD TO NEAR 86W WHERE IT DISSIPATES IN DRY ALOFT. THE RIDGE WILL SHIFT EASTWARD THROUGH TODAY AS IT WEAKENS. BY TONIGHT A SHORTWAVE TROUGH CLIPS THE N CENTRAL AND NE PORTIONS OF THE GULF...BUT HAVE LITTLE INFLUENCE ON WEATHER CONDITIONS AS THERE WILL BE LITTLE ATMOSPHERIC MOISTURE FOR IT TO WORK WITH TO KICK OFF ANY SHOWER/TSTMS ACTIVITY. WITH THE UPPER RIDGING...THE PRESENT SURFACE RIDGE WILL ALSO WEAKEN TODAY. THE PRES GRADIENT BRINGING THE NE 20 KT TO SOME OF THE SRN GULF WATERS OF THE MIDDLE AND EASTERN GULF WILL SLACKEN LATE TODAY AND TONIGHT ALLOWING FOR THOSE WINDS TO DIMINISH TO 10-15 KT. SEAS OF 5-7 FT THERE WILL RESPOND BY LOWERING TO 4-6 FT THROUGH THU...THEN LOWER FURTHER TO 3-5 FT FRI AND TO 2-3 FT LATE FRI AND SAT. CONDITIONS ELSEWHERE ARE EXPECTED TO REMAIN VERY NEAR THE SAME THROUGH FRI AS STRONGER CONTINENTAL SURFACE HIGH PRES THEN BUILDS SEWD OVER MUCH OF THE GULF WED AND THU BEFORE IT BEGINS TO WEAKEN AND SHIFT EASTWARD ON FRI. THIS WILL FOR A COLD FRONT TO MOVE INTO THE FAR N PORTIONS OF THE GULF AS SUGGESTED BY THE MODELS. LATEST GFS/ECMWF/NOGAPS 10 M WIND INDICATES THAT STRONG HIGH PRES BEHIND THE FRONT WILL INDUCE A PRES GRADIENT OVER THE FAR NW AND N CENTRAL WATERS ON SAT TO BRING N-NE 20 KT WINDS THERE ON SAT. N-NE WINDS OF 10-15 KT ARE FORECAST ELSEWHERE OVER THE GULF ON SAT. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... THE HIGH RESOLUTION ASCAT SWATH FROM 0240 UTC LAST NIGHT REVEALED N-NE WINDS OF 10-15 KT OVER THE FAR WRN CARIBBEAN N OF 15N...AND HIGHER WINDS FROM THE NW-N AT 20-25 KT IN THE FAR SW PORTION FROM ABOUT 12N TO 14N AND W OF 82W. THIS SAME PASS SHOWED NE-E WINDS OF 10-15 KT IN THE MIDDLE PORTION OF THE SEA WITH 15-20 KT WINDS S OF 14N BETWEEN 70W-76W. A 0100 UTC ASCAT PASS REVEALED ELY WINDS OF 10-15 KT ACROSS THE WRN PORTION OF THE TROPICAL N ATLC ZONES. SEA STATE...SEAS RANGE FROM 3-4 FT ACROSS MOST OF THE CARIBBEAN EXCEPT FOR 2-3 FT N OF ABOUT 16N BETWEEN PUERTO RICO AND WESTERN CUBA...AND A SMALL POCKET OF 6-8 FT IN THE FAR SW CARIBBEAN IN THE AREA OF NW-N 20-25 KT WINDS. THE CURRENT SYNOPTIC PATTERN IS FORECAST BY MODELS TO REMAIN IN PLACE THROUGH TONIGHT. THEREAFTER...STRONGER HIGH PRES SURGES S FROM THE GULF OF MEXICO TO OVER THE WESTERN CARIBBEAN WED AND THU BRINGING INCREASING N WINDS OF 20 KT MUCH OF THE NW CARIBBEAN WATERS WITH SEAS BUILDING TO AROUND 7 FT. THE N WINDS OF 20-25 KT OVER A PORTION OF THE SW CARIBBEAN ARE FURTHER REINFORCED BY THE NLY HIGH PRES SURGE AND APPEAR BASED ON GFS/ECMWF THAT THEY WILL CONTINUE INTO SAT MAYBE NOT ALL TIMES AT 20-25 KT...BUT INSTEAD 20 KT. THE WIND CONDITIONS OF 10-15 KT ACROSS THE TROPICAL N ATLC ARE FORECAST BY THE GFS/ECMWF TO HOLD THROUGH SAT WHILE VEERING TO THE SE-S IN RESPONSE TO THE ATLC COLD FRONTS AND TROUGHS ADVANCING EASTWARD THROUGH THE NRN WATER OF THE TROPICAL N ATLC BEGINNING LATE THU AND INTO SAT. LONG PERIOD NE SWELLS THERE RESULTING IN COMBINED SEAS OF UP TO 6 FT ARE FORECAST BY THE GRIDDED WWWIII GUIDANCE TO SUBSIDE TO 3-5 FT TODAY AND CONTINUE THROUGH SAT. SATELLITE IMAGERY HAS BEEN HIGHLIGHTING...AND IS CURRENTLY SHOWING AMPLE DEEP ATMOSPHERIC MOISTURE CONFINED TO THE SW SECTION OF THE CARIBBEAN. THIS MOISTURE IS IN THE FORM OF MULTILAYERED CLOUDS WITH SCATTERED SHOWERS AND TSTMS AIDED BY A PERSISTENT UPPER TROUGH IN THE NW CARIBBEAN THAT EXTENDS SWWD FROM CENTRAL CUBA TO GULF OF HONDURAS. THIS ACTIVITY HAS DIMINISH SOME SINCE YESTERDAY...AND IS EXPECTED TO CONTINUE TO DOE SO THROUGH THU. SW N ATLC W OF 55W... THE PRELIMINARY 0600 UTC SURFACE ANALYSIS HAS A WEAKENING 1010 MB LOW AT 28N74W WITH A TRAILING COLD FRONT SSW TO WRN CUBA. TO ITS E...A TROUGH EXTENDS FROM JUST E OF THE FORECAST WATERS AT 31N64W SW TO OVER THE FAR SE WATERS AND TO NEAR NE HISPANIOLA. SATELLITE IMAGERY SHOWS ABUNDANT DEEP ATMOSPHERIC MOISTURE WITH SCATTERED SHOWERS AND ISOLATED TSTMS CONTINUING OVER THE SE PORTION OF THE FORECAST ZONES ASSOCIATED WITH THE TROUGH...FURTHER AIDED BY AN UPPER LEVEL TROUGH THAT EXTENDS FROM AN UPPER LEVEL LOW AT 31N70W SSW TO CENTRAL CUBA. SCATTERED TSTMS MOVING NE ARE ALSO OVER THE FAR NE ZONE. THE 0240 UTC HIGH RESOLUTION ASCAT PASS NOTED GENERALLY LIGHT TO MODERATE SE-S WNDS OVER THE EASTERN PORTION OF THE BASIN E OF THE TROUGH...AND NLY WINDS BEHIND THE LOW AND COLD FRONT WITH AN AREA OF N-NE 20-30 KT WINDS N OF 28N W OF 76W BEHIND A A SECOND AND STRONGER COLD FRONT. BUOYS IN THAT VICINITY ARE REPORTING COMBINED SEAS OF 8-11 FT. OBSERVED SEAS ELSEWHERE ARE IN THE 5-7 FT RANGE IN A NE SWELL TO THE NE OF THE BAHAMAS WITH SEAS OF 6-8 FT N OF 27N E OF 78W. THE PRES DIFFERENCE BETWEEN THE LOW AND STRONG HIGH PRES RIDGING TO ITS N AND NW WILL MAINTAIN WILL SLOWLY EASE THROUGH WED AS THE LOW WEAKENS TO EVENTUAL DISSIPATION AS THE SECOND COLD FRONT OVERTAKES THE FRONT ASSOCIATED WITH THE LOW. THIS FRONT WILL THEN SWEEP ACROSS THE AREA THROUGH FRI AFTER MERGING WITH THE PERSISTENT SURFACE TROUGH DESCRIBED ABOVE. GLOBAL MODELS ARE CONSISTENTLY DEPICTING THAT STRONG HIGH PRES BEHIND THE FRONT WILL BUILD SE OVER THE ENTIRE BASIN THROUGH FRI...AND WEAKEN MOST ZONES SAT AS YET ANOTHER COLD FRONT ENTERS THE FAR NW WATERS. THE 20-30 KT WINDS N OF 28N W OF 78W DIMINISH TO 20-25 KT WED BUT SPREAD SWD IN BEHIND THE SECOND COLD FRONT FOLLOWED BY STRONG HIGH PRES. THESE WINDS ARE FORECAST TO DIMINISH TO 15-20 KT OVER THE WRN AND CENTRAL PORTIONS FRI AS THE HIGH PRES WEAKENS. HOWEVER IN THE NE PORTION OF THE EASTERN ZONES THE PRES GRADIENT WILL BE VERY TIGHT ON FRI. THE SEAS OF 8-11 FT IN THE NW PORTION WILL BE FURTHER REINFORCED BY ANOTHER BATCH OF LARGE N SWELLS THAT FOLLOWS IN BEHIND THE SECOND FRONT WITH THE HIGH PRES SURGE. A COMPLEX LOW PRES GYRE JUST N OF THE AREA FROM WHICH THE FRONT WILL BE TIED TO WILL CONSOLIDATE INTO ONE LOW BY FRI...AND WHILE DEEPENING. MODELS DIFFER ON EXACT PRES AND FORECAST PSNS OF THE LOW. THE MAIN THING TO NOTE IS THAT THE GFS MODEL GUIDANCE TO INDICATE THAT A VERY TIGHT PRES GRADIENT SETS UP OVER THE NE WATERS ON FRI WITH NW-N WINDS OF 30-40 KT...WHILE THE ECMWF ALTHOUGH NOT AS AGGRESSIVE DEPICTS NW-N WINDS OF 25-30 KT FOR THAT SAME PART OF THE BASIN ON FRI. THE GFS CARRIES A DEEPER LOW N OF THE AREA...WHILE THE ECMWF IS WEAKER AND FURTHER S WITH THE LOW. I AM THINKING THAT THE GFS WINDS MAY BE TOO HIGH FOR FRI ACROSS THAT PORTION OF THE FORECAST WATERS DUE TO PERHAPS FEEDBACK ISSUES. SO WILL LEAN CLOSER TO THE ECMWF/UKMET FOR NOW AND FORECAST W-NW WINDS OF 20-30 KT FOR THE NE ZONE ON FRI. BY LATE FRI AND INTO SAT...THE RESPONSIBLE PRES GRADIENT LIFTS NE AND THE STRONG WINDS DIMINISH TO NW-N AT 15-20 KT OVER THE NE WATERS. FOR SEAS...THE SEAS OF 8-11 FT IN THE WRN PORTION N OF THE BAHAMAS WILL BE FURTHER REINFORCED BY ANOTHER BATCH OF LARGE N SWELLS THAT FOLLOWS IN BEHIND THE SECOND FRONT WITH THE HIGH PRES SURGE AS DESCRIBED ABOVE. IN REFERENCE TO THE CENTRAL AND NE PORTIONS OF THE BASIN MAX HEIGHTS ARE FORECAST BY THE GRIDDED NOAA III WAVEWATCH GUIDANCE AND TO NOT AS LARGE AN EXTENT THE ECMWF WAVE GUIDANCE TO BUILD TO HIGH LEVELS (POSSIBLY TO 16 OR 17 FT) OVER THE N CENTRAL AND NE WATERS THU AND SPREAD SSE ACROSS MUCH OF THE CENTRAL AND ERN WATERS FRI AND SAT. WILL MAKE UPDATES TO LONG TERM PORTION OF THE FORECAST AS NEEDED BASED ON FUTURE MODEL TRENDS. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE GULF OF MEXICO... .NONE. CARIBBEAN SEA AND TROPICAL N ATLC... .NONE. SW N ATLANTIC... .NONE. 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