000 AGXX40 KNHC 041901 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 300 PM EDT FRI MAY 04 2012 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... SHARP MID TO UPPER TROUGH ACROSS E GULF CONTINUES TO GENERATE INSTABILITY AS IS MOVES SLOWLY E...WITH LINGERING ABUNDANT MOISTURE STILL BELOW...E OF 86W. TRIGGERING TROUGH FORECAST TO MOVE E ACROSS FLORIDA TONIGHT AND BE REPLACED BY UPPER CONVERGENCE AND PUT AN END TO THIS ACTIVE WEATHER. OTHERWISE... A QUIET PERIOD IS ON TAP FOR THE GULF OF MEXICO WITH WINDS EXPECTED TO REMAIN AT 15 KT OR LOWER AND SEAS NO HIGHER THAN 5 FT THROUGH TUE. THE NEXT THREAT OF ORGANIZED PRECIPITATION COMES LATE SUN OVER THE NE GULF AHEAD OF A BACKDOOR COLD FRONT DROPPING INTO NE FL. A DEEP LAYER TROUGH WILL BUILD OVER THE MISSISSIPPI VALLEY MON AND SHIFT EASTWARD TUE...KEEPING THE THREAT OF PRECIPITATION GOING OVER THE NE GULF ON ITS LEADING EDGE. AS WILL BE DISCUSSED BELOW IN ATLC SECTION...DIFFERENCES EXIST IN TIMING AND PLACEMENT OF THIS BACKDOOR FRONT...AND AT THIS TIME HAVE CHOSEN TO GO WITH A ECMWF/UKMET CONSENSUS...WHICH HAS FRONT SHIFTING SW INTO FLORIDA SLOWER THAN GFS. CARIBBEAN SEA... DEEP LAYERED TROUGHING DIGGING INTO THE CENTRAL ATLC HAS DISRUPTED THE SUBTROPICAL RIDGING INFLUENCING THE CARIBBEAN AND FURTHER WEAKENED THE PRES GRADIENT...YIELDING LIGHT TO MODERATE WINDS AND SEAS 6 FT OR LESS. THESE CONDITIONS ARE EXPECTED TO CONTINUE THROUGH TUE. THERE IS DISAGREEMENT BETWEEN THE LATEST GLOBAL MODELS ON THE STRENGTH AND TIMING OF THE CURRENT TROUGHING ACROSS THE E GULF AND W ATLC PHASING WITH THE BROAD TROUGH ACROSS THE N ATLC. AGAIN A SOLUTION LEANING MORE TOWARD THE ECMWF/UKMET CONSENSUS LLVL TROUGH ACROSS THE NE CARIB ATTM IS WASHING OUT WITH LLVL ENERGY AND MOISTURE SHIFTING WSW INTO HISPANIOLA...WHILE A NEW TROUGH IS FORMING FROM JUST S OF PUERTO RICO NE INTO THE OPEN ATLC. THIS TROUGH WILL MEANDER AND EVENTUALLY BECOME MORE ENE TO WSW ALIGNED OVER THE WEEKEND AND WEAKLY LINK WITH FRONTAL TROUGH SINKING INTO THE CENTRAL ATLC NEXT FEW DAYS. THIS WILL LEAD TO BROAD TROUGHING ACROSS NE AND CENTRAL CARIB AND VERY WEAK FLOW...WITH MODELS SUGGESTING WEAK LOW LIFTING OUT OF NRN S AMERICA INTO S CENTRAL CARIB...AND EPAC MONSOON SEASON COMMENCING. ATLC... WEAK 1020 MB HIGH REMAINS NEAR 30N77W AS DEEP LAYERED LOW IS DIGGING SSE ACROSS THE W ATLC ALONG 67W. ASSOCIATED FRONTAL BOUNDARY SINKING S ALSO AND FORECAST TO SHIFT SE THROUGH SAT AND EXIT THE AREA. SOME LINGERING 15 TO NEAR 20 KT WINDS REMAIN THROUGH STRAITS OF FLORIDA AND WINDWARD PASSAGES BUT WILL WEAKEN FURTHER THIS EVENING TO LIMIT 20 KT FLOW E OF AREA. BACKDOOR FRONT MENTIONED ABOVE WILL SINK INTO NW PORTIONS EARLY MON WITH 20 KT OF N TO NE FLOW OCCURRING ON POLEWARD SIDE THEN SHIFT SW INTO FL PENINSULA TUE. BROAD AND DEEP LOW PRES TO DEVELOP ACROSS NE ATLC DURING THIS TIME TO GENERATE LARGE N TO NE SWELL THAT WILL AFFECT E PORTIONS OF AREA LATER IN THE WEEK. OTHERWISE...LIGHT TO MODERATE WINDS WILL PREVAIL...WITH TROUGH OR WEAKNESS PERSISTING FROM NE CARIB NE INTO CENTRAL ATLC. 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 STRIPLING