000 AGXX40 KNHC 120703 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 305 AM EDT THU MAY 12 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 ATLC... A DEEP LAYERED LOW CENTERED JUST N OF THE AREA HAS SENT A WEAKENING COLD FRONT SOUTHWARD THROUGH MUCH OF THE AREA AND NOW LIES ALONG 21N E OF THE BAHAMAS INTO THE N PORTION OF THE TROPICAL N ATLC ZONE. THE PRIMARY SURFACE LOW ASSOCIATED WITH THE DEEP LAYERED LOW IS NORTH OF BERMUDA AROUND 36N. IT CONTINUES TO SUPPLY NORTHERLY SWELL IN THE 8-12 FT RANGE TO MUCH OF THE AREA AS WELL AS WIDESPREAD FRESH W WINDS OVER N WATERS WHICH WILL PERSIST THROUGH FRI. BY SAT...THE BROAD SURFACE LOW PRES BEGINS TO MOVE NE AND WINDS DIMINISH FURTHER. THE MODELS ARE IN REASONABLE AGREEMENT WITH THIS SCENARIO. A NEW FRONT MOVES TO THE SE UNITED STATES COAST SUN AND GETS HUNG UP THERE AS ITS IMPETUS VORT ALOFT IS FORCED NORTHWARD AS A NEW VORT DROPS INTO THE BACKSIDE OF THE TROUGH OVER THE OHIO VALLEY. THIS SECOND VORT SWINGS E MON AND CARRIES THE FRONT OFFSHORE MON NIGHT. CONSIDERING THE COMPLEXITY IN THE FORECAST MODELS ARE NOT THAT DIFFERENT AT THE SURFACE WITH THIS FRONTAL SCENARIO. THE GFS BUILDS STRONGER SOUTHERLY FLOW AHEAD OF THE FRONT ON SUN THAN THE ECMWF AND UKMET. THE ECMWF HAS TRENDED TOWARD A DEEPER SCENARIO THAN ITS RUN THIS TIME YESTERDAY. HOWEVER...WILL HOLD OFF ON 25 KT WINDS FOR NOW AS THERE ARE A LOT OF ELEMENTS THAT NEED TO COME TOGETHER BEFORE THEN FOR THIS SYSTEM TO BE THAT STRONG. THE UKMET IS A STRONG OUTLIER EARLY NEXT WEEK WHEN IT ALLOWS SOME ENERGY FROM THE DEEP LAYER TROUGH CURRENTLY OVER THE AREA TO LINGER OVER HISPANIOLA AND THEN LIFT NORTHWARD MON WITH A 1009 MB SURFACE LOW REFLECTION OVER E WATERS OF THE SW N ATLC MON NIGHT. CARIBBEAN... WITH THE SUBTROPICAL RIDGE SHIFTED WELL E BY THE DEEP LAYERED TROUGHING OVER THE CENTRAL ATLC...ONLY GENTLE TO MODERATE TRADES CAN BE FOUND OVER MUCH OF THE EASTERN AND CENTRAL CARIBBEAN WITH FRESH TRADES CONFINED TO THE FAR SOUTHERN TROPICAL ATLC ZONE. DEEP SOUTHERLY FLOW ON THE EASTERN SIDE OF THE DEEP LAYER LOW IN THE CENTRAL ATLC IS TRANSPORTING MOISTURE NORTHEASTWARD ACROSS THE CARIBBEAN AND IS SUPPLYING FUEL FOR PRECIPITATION PRIMARILY E OF 75W. A DISSIPATING COLD FRONT ASSOCIATED WITH THE DEEP LAYERED LOW TO THE N WILL SAG SOUTHWARD AND GET HUNG UP NEAR PUERTO RICO AS IT TURNS MORE MERIDIONAL...PROVIDING A FOCUS FOR SHOWERS. AS THE DEEP LAYERED LOW TO THE N BREAKS UP OVER THE WEEKEND...THE SUBTROPICAL RIDGE WILL BUILD IN FROM THE E AND INCREASE THE GRADIENT BETWEEN IT AND LINGERING TROUGHING OVER THE CENTRAL CARIBBEAN. THE GFS ALLOWS SE WINDS TO INCREASE TO 20 KT OVER THE EASTERN CARIBBEAN AS A RESULT. CONFIDENCE IS LOW IN THE AMOUNT OF TROUGHING EXPECTED OVER THE CENTRAL CARIBBEAN BY THAT TIME...SO WILL HOLD OFF ON BUILDING WINDS THAT STRONG OVER THE EASTERN CARIBBEAN. MEANWHILE...THE PRES GRADIENT BETWEEN STATIONARY HIGH PRES OVER THE NE GULF OF MEXICO AND AMPLIFYING TROUGHING OVER THE U.S. SOUTHERN PLAINS AND NORTHERN MEXICO HAS INDUCED FRESH TO STRONG SW FLOW OVER THE AND GULF OF HONDURAS. THE 0324 UTC ASCAT PASS CONFIRMS THESE CONDITIONS. WINDS HERE WILL GRADUALLY DIMINISH TO LESS THAN 20 KT BY FRI AS THE HIGH PRES TO THE N WEAKENS IN ADVANCE OF A WEAK COLD FRONT EXPECTED TO MOVE THROUGH THE NORTHERN GULF OF MEXICO. SAW NO REASON TO STRAY FAR FROM THE GFS FORECAST HERE. GULF OF MEXICO... AFTER DAYS WITH HIGH PRES OVER THE NE GULF AND LOWER PRES OVER SOUTHERN U.S. PLAINS AND NORTHERN MEXICO FORCING FRESH TO STRONG SE RETURN FLOW OVER THE WESTERN GULF...THE PATTERN IS FINALLY BEGINNING TO CHANGE. BY SAT...A FRONT IS EXPECTED TO MOVE EASTWARD INTO THE NW GULF AND THROUGH THE LOWER MISSISSIPPI VALLEY. THIS WILL WEAKEN THE HIGH PRES CENTER AND DISPLACE IT SLIGHTLY SOUTHWARD BEGINNING FRI...WEAKENING THE WINDS ACROSS THE WESTERN GULF. THE MODELS HAVE COME INTO BETTER AGREEMENT ON HAVING THE FRONT JUST OFF THE TX COAST VERY EARLY SAT MORNING AND CARRYING IT FROM THE FLORIDA BIG BEND TO BROWNSVILLE SUN MORNING. THE GFS IS A BIT STRONGER THAN THE OTHER MODELS WITH THE WIND FIELD NEAR THE FRONT...BUT IS NOT TOO FAR OUT OF ALIGNMENT WITH THE UKMET AND ECMWF. ITS SOLUTION SEEMS AS GOOD AS ANY WITH THE MULTIPLE IMPULSES EXPECTED TO PASS THROUGH THE NE GULF REINFORCING THE LEAD FRONT LATE SUN INTO MON. WARNINGS.. ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER