000 AGXX40 KNHC 211807 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 210 PM EDT SUN OCT 21 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... THE STATIONARY FRONT ACROSS THE FAR SOUTHERN GULF FROM THE STRAITS OF FLORIDA TO THE YUCATAN CHANNEL SHOULD DISSIPATE THIS AFTERNOON. A HIGH PRES RIDGE WILL BUILD BEHIND THE FRONT WITH WINDS BECOMING FRESH OVER MUCH OF THE GULF SUN NIGHT THROUGH MON NIGHT. UNCERTAINTY COMES INTO THE FORECAST ON TUE WHEN THE PATTERN IN THE GULF BECOMES DEPENDENT ON THE EVOLUTION OF THE SYSTEM IN THE SW CARIBBEAN SEA. PLEASE SEE THE CARIBBEAN SEA SECTION BELOW FOR DETAILS. THE PRES GRADIENT IS EXPECTED TO BUILD OVER THE EASTERN GULF BETWEEN HIGH PRES OVER THE SOUTHERN APPALACHIAN MOUNTAINS AND DEEPENING LOW PRES EXPECTED TO LIFT NORTHWARD THROUGH THE WESTERN CARIBBEAN TOWARD EASTERN CUBA BY THU. THE MODELS CONTINUE TO AGREE ON THIS GENERAL PATTERN. THE 12Z GFS FORECAST APPEARS REASONABLE FOR THE MAJORITY OF THE PERIOD AND IS CLOSE TO THE MEDIUM RANGE POINTS AGREED TO DURING THE NHC/HPC COORDINATION CALL. MARINERS SHOULD USE CAUTION IN THE STRAITS OF FLORIDA WHERE NE TO E WINDS SHOULD REMAIN FRESH TO STRONG FROM TONIGHT THROUGH FRI. CARIBBEAN SEA AND TROPICAL N ATLC... THE TROPICAL WAVE ALONG 76W WITH A SPOT LOW AT 15N WILL CONTINUE TO MOVE W TO 79W THROUGH MON AS IT MERGES WITH THE MONSOONAL TROUGH THAT STRETCHES FROM THE E PACIFIC INTO THE SW CARIBBEAN. ON MON...UPPER DIFFLUENCE ASSOCIATED WITH THE THE REAR RIGHT QUADRANT OF THE SOUTHERN STREAM UPPER JET THAT IS FORECAST TO SPLINTER AWAY FROM THE DEEP LAYER TROUGH CURRENTLY OVER THE GULF OF MEXICO WILL ENHANCE CONVECTION OVER THE MOISTURE RICH SW CARIBBEAN. THE MODELS AGREE ON DEEPENING THE LOW PRES SYSTEM AS IT AS IT LIFTS NORTHWARD TOWARD EASTERN CUBA...POSSIBLY AS A TROPICAL CYCLONE...MON NIGHT THROUGH THU. DURING THAT TIME...AN UPPER TROUGH ON THE W SIDE OF THE JET WILL AMPLIFY... WITH THE DEEP LEVEL STEERING FLOW BECOMING MORE S TO N. THE 12Z GFS HAS TRENDED MORE TO THE W WITH THE LOW TRACK TUE-FRI. THIS IS MORE IN LINE WITH THE MODEL CONSENSUS AND THE NHC/HPC MEDIUM RANGE COORDINATED POINT FOR THE SYSTEM. WINDS WERE CAPPED AT 30 KT FOR NOW GIVEN THE UNCERTAINTY IN THE FORECAST AND THE LACK OF A CLEAR CIRCULATION AT THE PRESENT TIME. THE 12Z GFS DOES NOT SHOW GALE/T.S. FORCE WINDS NEAR THE CENTER OF THE SYSTEM UNTIL WED OVER THE WINDWARD PASSAGE...BUT DOES CARRY A GALE IN THE SAME LOCATION WELL AWAY FROM THE CENTER BY TUE EVENING. SW N ATLC... THE COLD FRONT FROM 31N70W TO THE STRAITS OF FLORIDA WILL CONTINUE TO WEAKEN AS IT PASSES EASTWARD...MOVING E OF 65W MON. HIGH PRES WILL BUILD BEHIND THE FRONT SUN NIGHT THROUGH TUE...WITH WINDS BECOMING FRESH W OF 78W TONIGHT AND ACROSS MUCH OF THE SW N ATLC BY MON NIGHT. CONFIDENCE DIMINISHES BEGINNING MON NIGHT AS THE PRES GRADIENT BUILDS BETWEEN HIGH PRES ANCHORED OVER THE SOUTHERN APPALACHIAN MOUNTAINS AND DEVELOPING LOW PRES IN THE SW CARIBBEAN. SEE THE SECTION ABOVE FOR DETAILS ON THE CARIBBEAN SYSTEM. THE MODELS GENERALLY AGREE ON LIFTING A LOW PRES SYSTEM...POSSIBLY A TROPICAL CYCLONE...NORTHWARD TOWARD EASTERN CUBA MON NIGHT THROUGH THU ON THE LEADING EDGE OF AN AMPLIFYING UPPER TROUGH AND INTO THE CENTRAL BAHAMAS BY FRI. THE 12Z GFS SEEMS REASONABLE FOR THE MAJORITY OF THE FORECAST PERIOD AND CLOSELY RESEMBLES THE NHC/HPC COORDINATED SCENARIO FOR THE LOW PRES SYSTEM LIFTING NORTHWARD INTO THE SW N ATLC. HOWEVER...DID NOT RAISE WINDS ABOVE THE 30 KT THRESHOLD WHICH KEEPS SEAS E OF THE BAHAMAS CAPPED TO 15 FT THROUGH FRI. 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. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER