000 AGXX40 KNHC 300719 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 320 AM EDT TUE OCT 30 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... WINDS HAVE DIMINISHED OVER MUCH OF THE WESTERN GULF. A FRESH TO STRONG N-NW BREEZE CONTINUES OVER THE E GULF...OBSERVED BY THE 0316 UTC ASCAT PASS...AS A RESULT OF THE PRES GRADIENT BETWEEN BUILDING COLD HIGH PRES OVER THE CENTRAL MISSISSIPPI VALLEY SPILLING OUT ACROSS THE GULF AND LARGE AND THE EXPANSIVE AREA OF LOW PRES TO THE E ASSOCIATED WITH POST-TROPICAL CYCLONE SANDY WELL N OF THE REGION. THESE WINDS WILL GRADUALLY DIMINISH TO 20 KT OR LESS BY WED MORNING BASIN WIDE AS THE HIGH SHIFTS SOUTHWARD SETTLING OVER THE CENTRAL GULF WED. A WEAK COLD FRONT OR TROUGH WILL ROTATE THROUGH THE N CENTRAL AND NE GULF THU WITH LITTLE IMPACT TO SENSIBLE WEATHER OTHER THAN A WIND SHIFT. NEW HIGH PRES WILL QUICKLY BUILD IN BEHIND THE FRONT OR TROUGH LATE THU THROUGH SAT. BY THU THROUGH SAT...LIGHT TO MODERATE WINDS AND PRIMARILY 2-3 FT WILL PREVAIL ACROSS THE GULF. THE 00Z GFS AND ECMWF ARE IN AGREEMENT ON THIS FORECAST. THE 00Z GFS AND WW3 GUIDANCE WAS BLENDED WITH CONTINUITY TO UPDATE THE FORECAST. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... A DISTINCT WIND SHIFT IS NOTED BY THE 0132 UTC ASCAT PASS ON EITHER SIDE OF A WEAK SURFACE TROUGH FROM 18N68W TO 11N71W...WITH A LIGHT TO GENTLE BREEZE ON THE W SIDE OF THE TROUGH AND A GENTLE TO MODERATE BREEZE E OF THE TROUGH WHERE THE PRES GRADIENT IS STRONGEST BETWEEN THIS TROUGH AND RIDGING OVER THE TROPICAL N ATLC. ONLY ISOLATED SHOWERS AND THUNDERSTORMS ARE CURRENTLY NOTED NEAR THE TROUGH AND ALONG THE ADJACENT COAST OF COLOMBIA AND VENEZUELA. MOISTURE FROM THE S IS BEING ADVECTED TO THE NE BY SW FLOW IN THE MID AND UPPER LEVELS. CONVECTIVE ACTIVITY NEAR THE TROUGH IS EXPECTED TO EXPAND LATE WED INTO THU AS THE SURFACE TROUGH PASSES UNDER THE REAR RIGHT QUADRANT OF THE SOUTH-SOUTHWESTERLY UPPER JET. THIS TROUGH IS FORECAST TO DRIFT WESTWARD DURING THE NEXT FEW DAYS...REACHING 80W BY FRI MORNING WHEN WEAK LOW PRES MAY DEVELOP ALONG IT NEAR 11N PRIOR TO THE TROUGH REACHING CENTRAL AMERICA. THE 00Z GFS AND UKMET AGREE ON STRONGER WINDS ASSOCIATED WITH THE DEVELOPING LOW WHILE THE ECMWF IS WEAKER. WITH SUCH AN AMPLIFIED UPPER PATTERN ALOFT ALREADY IN PLACE...WILL SIDE WITH THE STRONGER GFS AND UKMET FOR NOW. THE 00Z GFS AND WW3 WERE BLENDED WITH CONTINUITY IN THE CARIBBEAN TO UPDATE THE FORECAST AS WELL AS IN THE TROPICAL N ATLC WHERE LARGE...LONG-PERIOD NW SWELL SPREADING OUTWARD FROM POST-TROPICAL CYCLONE SANDY WILL CONTINUE TO AFFECT THE ATLC/CARIBBEAN PASSAGES AND THE TROPICAL N ATLC WATERS THROUGH WED...SUBSIDING THU AND FRI. SOUTHWEST NORTH ATLC S OF 31N W OF 55W... SUSTAINED GALE FORCE WINDS ASSOCIATED WITH POST-TROPICAL SANDY HAVE MIGRATED N OF THE FORECAST AREA. BUOY OBSERVATIONS AND THE 0136 UTC ASCAT PASS SHOWED ANY NEAR GALE FORCE WINDS ARE CONFINED TO N OF 30N W OF 72W. THE EXPANSIVE...DEEP-LAYER CIRCULATION WILL SEE A FEW SURGES OF COLD...DRY AIR WITH NW WINDS MIXING TO THE SURFACE AS SHORTWAVE ENERGY WRAPS S OF THE MID TO UPPER LEVEL LOW THE THE N. WINDS ARE EXPECTED TO REMAIN BELOW GALE FORCE WITH THE 00Z GEFS SHOWING A ZERO PERCENT CHANCE OF GALE FORCE WINDS ANYWHERE S OF 32N THROUGH SAT. SEAS AS HIGH AS 16 FT CONTINUE TO LINGER IN THE REGION IN THE NW SWELL ASSOCIATED WITH POST-TROPICAL CYCLONE SANDY. LARGE LONG PERIOD NE SWELL IMPACTING NEARLY THE ENTIRE REGION...INCLUDING THE N SHORES OF THE NE CARIBBEAN ISLANDS...ARE EXPECTED TO DIMINISH TUE THROUGH WED. THE 00Z MODELS AGREE ON MARINE CONDITIONS IMPROVING SIGNIFICANTLY BY THU AND FRI. THE 00Z GFS AND WW3 WERE BLENDED WITH CONTINUITY FOR THE FORECAST. 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