000 AGXX40 KNHC 181849 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 150 PM EST FRI JAN 18 2013 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... THE AREA OF FRESH TO STRONG NE WINDS IS SHRINKING EASTWARD RAPIDLY TODAY....WITH WINDS ABOVE ADVISORY CRITERIA LIMITED TO THE NE GULF N OF 25N E OF 89W AS OF 1200 UTC. THESE CONDITIONS WERE CONFIRMED BY THE 1446 UTC ASCAT PASS AS WELL AS BUOY OBSERVATIONS. THE 1200 UTC GFS DOES NOT CARRY 25 KT WINDS HERE...NOR DO THE OTHER 1200 UTC GLOBAL MODELS OR THE 0000 UTC ECMWF. IN ADDITION...BUOY 42099 REPORTED 10 FT SEAS AT 1200 UTC WHILE THE MWW3 WAS APPROXIMATELY 2 FT TOO LOW. THE ECMWF WAVE MODEL AND THE FNMOC WAVE WERE BETTER INITIALIZED HERE BY HANGING ON TO LARGE NW SWELL LONGER THAN THE MWW3. ADJUSTMENTS WERE MADE TO THE INITIAL PERIOD AS WELL AS THE SHORT TERM FORECAST BASED ON THE OBSERVED CONDITIONS. WINDS AND SEAS WILL DIMINISH ACROSS THE ENTIRE GULF THROUGH THE WEEKEND AS BROAD HIGH PRES WEAKENS N OF THE AREA. BY MON...THICKNESSES FALL ACROSS THE NORTHERN GULF AS THE AMPLIFYING DEEP-LAYER LONG-WAVE TROUGH SENDS A SHOT OF COOLER AIR INTO THE REGION. HIGH PRES BUILDS NORTH OF THE AREA LATE MON INTO TUE AND BUTTS AGAINST SURFACE TROUGHING IN THE SW GULF OF MEXICO...ALLOWING FOR FRESH NE WINDS TO BUILD IN THE W CENTRAL GULF ON TUE. CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W... WINDS AND SEAS IN THE CENTRAL CARIBBEAN HAVE DIMINISHED AS THE DRIVING SUBTROPICAL RIDGE TO THE N HAS BEEN FORCED EASTWARD BY THE COLD FRONT THAT HAS INTRUDED INTO THE NW CARIBBEAN. THE 1448 UTC ASCAT PASS CONFIRMS A MODERATE BREEZE NEAR THE COAST OF COLOMBIA AND SHOWS FRESH TO STRONG N-NE FLOW BEHIND THE COLD FRONT OVER THE NW CARIBBEAN. AT 1200 UTC BUOY 42056 REPORTED 23 KT WINDS AND 10 FT SEAS. FUNNELING OF THE NORTHERLY FLOW BETWEEN THE LAND AND THE FRONT LIKELY RESULTED IN 30 KT WINDS AT 1200 UTC THIS MORNING...AS THE 1200 UTC GFS SHOWS. THIS GFS IS REASONABLY WELL INITIALIZED AND THE MWW3 WAS ONLY OFF FROM THE BUOY BY 1 FT. GIVEN THE GFS AND MWW3 PERFORMANCE IN THE GULF YESTERDAY AND TODAY...BELIEVE THERE IS SOME ROOM FOR THE WINDS AND SEAS TO BE SLIGHTLY HIGHER THAN THE GFS/MWW3 FORECAST HERE...WITH WINDS AND SWELL SLOWER TO SUBSIDE THAN THESE MODELS SUGGEST. HUNG ONTO ADVISORY CONDITIONS ONE 6 HOUR PERIOD LONGER THAN THE MODELS WHEN UPDATING THE GRIDS THIS MORNING IN ORDER TO TAKE THIS BIAS INTO ACCOUNT. THE COLD FRONT WILL STALL FROM CENTRAL CUBA TO CENTRAL HONDURAS TODAY AND BECOME DIFFUSE SAT. FRESH TO STRONG TRADES RETURN TO THE COAST OF COLOMBIA OVERNIGHT TONIGHT AS HIGH PRES BUILDS TO THE N BEHIND THE COLD FRONT. IN THE TROPICAL N ATLC...CONDITIONS WILL REMAIN BELOW ADVISORY CRITERIA UNTIL MON WHEN BUILDING HIGH PRES TO THE N EXPANDS THE AREA OF FRESH TRADES AND RAISES SEAS TO 8 FT. A SOLID AREA OF 20 KT WINDS WITH SEAS TO 9 FT IN EASTERLY SWELL SHOULD BE IN PLACE BY TUE. SW N ATLC S OF 31N W OF 55W... THE 1446 UTC ASCAT PASS SHOWED WINDS NEAR GALE FORCE IN THE WARNING AREA N OF 29N W OF 78W. BUOY 41012 CONSISTENTLY REPORTED WINDS NEAR 30 KT FROM 1150-1350 UTC WITH GUSTS ABOVE GALE FORCE. WINDS ARE DIMINISHING HERE GRADUALLY WITH THE 1750 UTC OBSERVATION SHOWING N-NE AT 25 KT GUSTS TO 31 KT. THE 1200 UTC GFS DID INITIALIZE GALE FORCE WINDS HERE THAT DIMINISH BY 1800 UTC. THE GALE WARNING WILL BE ALLOWED TO EXPIRE AT 1800 UTC AS THE RECENT SURROUNDING OBSERVATIONS CONFIRM THE DIMINISHING TREND IN THE WINDS. THE 0000 UTC ECMWF WAS 5-10 KT OFF THE OBSERVATIONS AT 1200 UTC...BUT ITS WAVE MODEL IS HANDLING THE SWELL CURRENTLY IN THE AREA BETTER THAN THE 1200 UTC MWW3 WHICH IS ABOUT 1-2 FT TOO LOW. ADJUSTMENTS WERE MADE ACCORDINGLY TO THE INITIAL TIME AND SHORT TERM FORECAST PERIODS AS THE WINDS AND SEAS DIMINISH THROUGH SAT. THE FRONT IS FORECAST TO BE HUNG UP OVER THE BAHAMAS THROUGH THE WEEKEND. BY MON...THE AMPLIFYING LONG-WAVE DEEP-LAYER TROUGH TO THE N WILL SEND A COLD FRONT INTO NW WATERS THAT WILL REINFORCE THE BOUNDARY. THERE IS CONSIDERABLE DISAGREEMENT ON THE EVOLUTION OF THE ANCHOR LOW WELL N OF THE AREA ASSOCIATED WITH THIS COLD FRONT. THE 1200 UTC GFS AND UKMET ARE FASTER AND CONSIDERABLY WEAKER THAN THE NOGAPS AND 0000 UTC ECMWF WITH THE LOW AS IT PASSES OFF THE CAROLINA COAST LATE MON/MON NIGHT. AS A RESULT...THE ECMWF HAS MUCH STRONGER FRONT OVER THE FORECAST AREA THAN THE GFS BY 1800 UTC TUE...WITH THE ECMWF SHOWING CONDITIONS ABOVE ADVISORY CRITERIA. THE ECMWF WAVE MODEL GENERATES SIGNIFICANTLY HIGHER SWELL THAN THE MWW3...WITH WAVE HEIGHT REACHING 8-9 FT IN N WATERS TUE AFTERNOON WHEN THE MWW3 ONLY SHOWS 4 FT. CONFIDENCE IS VERY LOW IN THIS MODEL SPLIT...SO A BLEND OF THE 1200 UTC GFS AND 0000 UTC ECMWF WAS USED TO ADJUST WINDS AND A BLEND OF THEIR CORRESPONDING WAVE MODELS WAS USED TO ADJUST SEAS IN THE ATLC N OF 27N LATE MON THROUGH TUE. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE WARNINGS... GULF OF MEXICO... .NONE. CARIBBEAN SEA AND TROPICAL N ATLC... .NONE. SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER