000 AGXX40 KNHC 281741 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 145 PM EDT SAT APR 28 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 BROAD TROUGH BETWEEN FLORIDA AND THE BAHAMAS IS MAKING ITS WAY WESTWARD INTO THE GULF WITH THE GFS CONTINUING TO BE A STRONG OUTLIER SOLUTION WITH ITS 12Z RUN BY SUN MORNING. THERE ARE SIGNIFICANT GRID SCALE FEEDBACK ISSUES WITH THE GFS THAT MAKE ITS FORECAST SUSPECT. FROM 06Z TO 12Z SUN...THE GFS STAMPS OUT 2.40 INCHES OF PRECIPITATION EAST OF THE GULF NEAR CAY SAL BANK AROUND 24N80W BUT ONLY 0.81 INCHES OF THAT IS ATTRIBUTED TO CONVECTION. THESE FEEDBACK ISSUES CONTINUE INTO TUESDAY AND CAUSE THE GFS TO BE THE ONLY MODEL TO DEVELOP A LOW PRES SYSTEM FROM THE TROUGH. A SOLUTION MORE IN LINE WITH A BLEND OF THE 00Z ECMWF AND UKMET WAS USED FOR THE LAST FORECAST PACKAGE. THIS MEANT MOVING A WEAKER OPEN TROUGH INTO THE EASTERN GULF MORE SLOWLY THAN THE GFS. CARIBBEAN SEA... SHOWERS AND THUNDERSTORMS CONTINUE OVER THE CARIBBEAN BETWEEN 72W AND 84W AS TROPICAL MOISTURE FROM THE PACIFIC AND SOUTHWEST CARIBBEAN IS PULLED INTO THE LEADING EDGE OF THE DEEP LAYER TROUGH ALONG 86W. LOOK FOR THESE CONDITIONS TO CONTINUE THROUGH THE WEEKEND BEFORE THE DEEP LAYER TROUGH BREAKS UP. AS MENTIONED IN THE GULF OF MEXICO SECTION ABOVE...THE GFS IS A STRONG OUTLIER WITH THE SURFACE REFLECTION OF THIS TROUGH WITH THE 12Z RUN CARRYING A 1010 MB LOW OVER WESTERN CUBA BY SUN EVENING. THE FAVORED FORECAST LEANED TOWARD THE 00Z ECMWF IN THE CARIBBEAN. THE ECMWF APPEARS TO HAVE A GOOD HANDLE ON THE MODERATE FRESH TRADES FOUND OVER MUCH OF THE CARIBBEAN ACCORDING TO OBSERVATIONS AND THE 1432 ASCAT PASS. ATLANTIC... AS MENTIONED IN THE GULF OF MEXICO SECTION ABOVE...THE 12Z GFS CONTINUES TO STRUGGLE WITH CONVECTIVE FEEDBACK ISSUES THAT MAKE ITS FORECAST UNRELIABLE. IN ADDITION TO THE PRECIPITATION PROBLEMS AS A RESULT OF THE FEEDBACK...THE GFS CARRIES 30 KT WINDS OVER THE CENTRAL BAHAMAS WESTWARD THROUGH THE STRAITS OF FLORIDA AND FLORIDA BAY SUN EVENING WHILE THE PREFERRED 12Z ECMWF AND UKMET CALL FOR 15-20 KT. THE ECMWF AND UKMET ARE ALSO SLOWER TO CARRY THIS TROUGH WESTWARD THROUGH THE STRAITS OF FLORIDA THAN THE GFS. IN THE TROPICAL N ATLC ZONE...FRESH TRADE WINDS WILL DOMINATE THE REGION THROUGH MON AND THEN DIMINISH A NOTCH AS THE DOMINANT HIGH PRES SYSTEM SWITCHES FROM THE CENTRAL ATLC TO THE WESTERN ATLC. THIS WILL WEAKEN THE PRES GRADIENT. 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