000 AGXX40 KNHC 050709 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 310 AM EDT SAT MAY 05 2012 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... THE QUIET PERIOD CONTINUES IN THE GULF OF MEXICO WITH WINDS EXPECTED TO REMAIN AT 15 KT OR LOWER AND SEAS NO HIGHER THAN 5 FT THROUGH WED. THE NEXT THREAT OF ORGANIZED PRECIPITATION COMES LATE SUN OVER THE NE GULF AHEAD OF A BACKDOOR COLD FRONT DROPPING INTO NE FL. ANOTHER WEAKER COLD FRONT WILL PASS THROUGH THE MISSISSIPPI VALLEY BY TUE...KEEPING THE THREAT OF PRECIPITATION GOING OVER THE NE GULF ON ITS LEADING EDGE THROUGH TUE. THIS COLD FRONT WILL REACH THE NORTHERN GULF COAST AT THE END OF THE PERIOD WED. A BLEND OF THE 00Z GFS AND ECMWF WAS USED TO ADJUST THE GRIDDED FORECAST. CARIBBEAN SEA... TROUGHING OVER THE CENTRAL ATLC HAS WEAKENED THE SUBTROPICAL RIDGING OVER THE CARIBBEAN AND LESSENED THE PRES GRADIENT YIELDING LIGHT TO MODERATE WINDS AND SEAS 5 FT OR LESS. THESE CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE END OF THE PERIOD ON WED. THERE IS SOME DISAGREEMENT BETWEEN THE MODELS ON THE STRENGTH OF THE TROUGHING EXPECTED OVER THE EASTERN CARIBBEAN MON THROUGH WED...WITH THE 00Z GFS SPORTING A WELL DEFINED LOW PRES SYSTEM WITH WINDS TO 20 KT. HOWEVER...THE 00Z UKMET AND 00Z ECMWF ARE NOT NEARLY AS WELL DEFINED WITH THE LOW AND DO NOT BUILD WINDS AS STRONG AS THE GFS. THE GFS DUMPS OUT NEARLY 3 INCHES OF PRECIPITATION IN 6 HOURS WITH THIS SYSTEM OVER THE EASTERN CARIBBEAN BETWEEN 18Z SUN AND 00Z MON AS WELL AS BETWEEN 00Z-06Z MON...WITH ONLY 0.50-0.75 INCHES OF THAT GENERATED FROM CONVECTIVE PROCESSES DURING EACH 6 HR PERIOD. THIS APPEARS TO BE A CASE OF GRID-SCALE FEEDBACK. WHILE CONFIDENCE IS LOW THAT THE SYSTEM WILL BE AS STRONG AS THE GFS...SUN THROUGH TUE LOOKS TO BE A WET PERIOD FOR THE LESSER ANTILLES AHEAD OF THIS TROUGH. A BLEND OF THE PREVIOUS FORECAST WAS BLENDED WITH THE ECMWF AND HEDGED SLIGHTLY TOWARD THE MORE ORGANIZED SOLUTION OF THE GFS. ATLANTIC... FOR THE TROPICAL N ATLC...PLEASE SEE THE DISCUSSION OF THE TROUGHING EXPECTED IN THE EASTERN CARIBBEAN LATER IN THE PERIOD IN THE SECTION ABOVE. THE BLEND OF THE PREVIOUS FORECAST WITH THE 00Z ECMWF ADJUSTED SLIGHTLY TOWARD THE MORE ORGANIZED 00Z GFS WAS USED HERE THROUGH WED WHEN THE TROUGH EMERGES INTO THE N HALF OF THE TROPICAL N ATLC ZONE. FARTHER N...THE MOST SIGNIFICANT MODEL DIFFERENCES LIE WITH THE COLD FRONT EXPECTED TO SWEEP S INTO THE SW N ATLC ZONE SUN NIGHT. THE MODELS ARE IN GOOD AGREEMENT ON CARRYING A 1010-1011 MB WAVE ALONG THE FRONT OFF THE N FL COAST EARLY MON MORNING AND SWEEP THE FRONT SOUTHEASTWARD WITH THE GENERAL TREND OVER THE LAST 24 HRS BEING TOWARD A WEAKER AND FASTER SOLUTION. THE WAVEWATCH HAS ALSO TRENDED TOWARD A SLOWER SWELL TRAIN WITH LOWER MAX WAVE HEIGHTS. A BLEND OF THE SIMILAR 00Z GFS AND 00Z ECMWF WAS PRIMARILY USED FOR THE FORECAST FROM SUN ONWARD...WITH MORE RELIANCE ON THE PREVIOUS FORECAST EARLY IN THE PERIOD. NOTE... EFFECTIVE APR 3, 2012 AT 1800 UTC THE OFFSHORE WATERS FORECAST ZONES CHANGED FOR THE CARIBBEAN AND SW N ATLANTIC AND THE GULF OF MEXICO. ISSUANCE TIME FOR THE GULF OF MEXICO OFFSHORE WATERS FORECASTS IS REFERENCED TO THE EASTERN TIME ZONE. FOR DETAILS SEE WWW.NHC.NOAA.GOV/ABOUTTAFBPROD.SHTML#OWF GRIDDED MARINE OUTPUT IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE (LOWER CASE). GULF OF MEXICO... .NONE. CARIBBEAN SEA... .NONE. ATLANTIC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER