000 AGXX40 KNHC 040650 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 250 AM EDT WED MAY 4 2011 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLC...AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. SW N ATLC AND TROPICAL N ATLC... A LOW PRES SYSTEM N OF THE AREA IS EXPECTED TO DROP S OF 30N BY THU MORNING INTO THE AREA JUST E OF 55W. THE 00Z GFS FORECAST FOR THE SYSTEM IS EXPECTED TO BE NEARLY 6 STANDARD DEVIATIONS DEEPER THAN THE MEAN PATTERN AT H5 OVERNIGHT TONIGHT. WHILE THIS IS AN UNUSUAL PATTERN...THE GFS IS IN REASONABLE AGREEMENT WITH THE 00Z ECMWF ON THE DEPTH OF THE SYSTEM AND ARE INITIALLY IN REASONABLE AGREEMENT WITH THE REMAINDER OF THE 00Z GUIDANCE. THE MAIN IMPACT OF THIS SYSTEM OVER THE FORECAST ARE IS SWELL. NORTHERLY SWELL ASSOCIATED WILL CONTINUE MAKING ITS WAY SOUTHWARD THROUGH THE EASTERN WATERS OF THE SW N ATLC TODAY AND DAMPEN AS IT MOVES THROUGH THE TROPICAL N ATLC TODAY THROUGH FRI. THERE HAVE BEEN SEVERAL REPORTS OF 10 FT SEAS BETWEEN BETWEEN 60W AND 65W N OF 27N THE LAST FEW HOURS...INCLUDING BUOY 41049. THE MWW3 IS PERFORMING WELL COMPARED TO THESE OBSERVATIONS. THIS SYSTEM WILL CONTINUE TO DISRUPT THE SUBTROPICAL RIDGE AND ASSOCIATED TRADE WINDS OVER THE TROPICAL N ATLC THROUGH THE PERIOD. A NEW COLD FRONT MOVES OFF THE N FL COAST LATER THIS MORNING. THE 00Z GFS AND ECMWF ARE IN REASONABLE AGREEMENT AND IN LINE WITH THE MODEL CONSENSUS WITH THE FRONTAL TIMING AND DISINTEGRATION OF THIS FRONT W OF 55W. THE GFS CARRIES STRONGER WINDS BEHIND THE FRONT THAN THE ECMWF THROUGH THU. THE UKMET AGREES WITH THE STRONGER GFS HERE AND THIS SEEMS REASONABLE GIVEN THE BUILDING PRES GRADIENT BETWEEN HIGH PRES W OF THE FRONT AND THE INCREASINGLY LOWER PRES ASSOCIATED WITH FRONT AS IT APPROACHES THE SYSTEM TO ITS E. CARIBBEAN... RAINFALL WILL CONTINUE TO BE THE MAIN WEATHER STORY OVER THE CARIBBEAN THIS FORECAST PERIOD WITH SATELLITE IMAGERY SHOWING DEEP CONVECTION PRIMARILY OVER NORTHERN COLOMBIA. PRECIPITABLE WATER IMAGERY SHOWS THE SLUG OF MOISTURE FOCUSED PRIMARILY IN THE S CENTRAL CARIBBEAN WITH A TONGUE THAT EXTENDS E INTO THE NORTHERN WINDWARD ISLANDS. PRECIPITABLE WATER VALUES AT OR ABOVE 50 MILLIMETERS ARE BEGINNING TO BE DISPLACED SOUTHWARD BY THE MID-LEVEL REMNANTS OF THE COLD FRONT ASSOCIATED WITH THE SYSTEM E OF THE SW N ATLC ZONE. MUCH OF THE PRECIPITATION IS EXPECTED TO SHIFT SOUTHWARD BY THU AS A RESULT. THE 0248 UTC ASCAT PASS REPORTED 25-30 KT WINDS IN THE WINDWARD PASSAGE. THE GFS IS THE ONLY 00Z MODEL TO SHOW 25 KT WINDS HERE. WILL STICK CLOSER TO ITS FORECAST EARLY IN THE PERIOD. THAT SAME ASCAT PASS SHOWED 20 KT WINDS OVER MUCH OF THE CENTRAL CARIBBEAN. WINDS SHOULD DIMINISH BELOW ADVISORY CRITERIA OVER MOST OF THAT AREA THU AND FRI AS A COLD FRONT MOVES N OF THE AREA AND DISRUPTS THE PRES GRADIENT BETWEEN HIGH PRES TO THE N AND LOWER PRES OVER S AMERICA. GULF OF MEXICO... A COLD FRONT TRAVERSES THE GULF OF MEXICO FROM ITS NE TO SW. THE 0312 UTC AND 1638 UTC ASCAT PASSES FROM 3 MAY NEVER SHOWED GALE FORCE WINDS BEHIND THE FRONT. THE 00Z GFS KEEPS WINDS TO 30 KT IN THE W BAY OF CAMPECHE TODAY AND THEN RAPIDLY DIMINISHES THE WINDS EVERYWHERE BEHIND THE FRONT BY THU. THE MODELS HAVE TRENDED TOWARD ALLOWING THE WESTERN EDGE OF THE DISSIPATING FRONTAL BOUNDARY TO LIFT NORTHWARD OVER THE SE GULF ON THU AND CONTINUE W TOWARD THE CENTRAL GULF AS A TROUGH BEFORE BEING FORCED BACK E BY THE SOUTHERN EDGE OF A DEEP LAYER TROUGH PASSING THROUGH THE FAR SE U.S. THE MAIN IMPACT OF THIS PATTERN WILL BE A SLIGHTLY HIGHER CHANCE OF SHOWERS AND ISOLATED TSTMS OVER THE SE GULF THU AND FRI. HIGH PRES BEHIND THE DEEP LAYER TROUGH PASSING THROUGH THE SOUTHEASTERN U.S. WILL DOMINATE THE PATTERN IN THE GULF OVER THE WEEKEND. WARNINGS... ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER