000 AGXX40 KNHC 211832 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 235 PM EDT THU JUN 21 2012 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... THE BIGGEST QUESTION IN THE GULF OF MEXICO LIES WITH THE GFS FORECAST: IS THE PIECEMEAL EVOLUTION OF THE LOW PRES SYSTEM SEEN IN MANY OF THE GFS FORECAST RUNS OVER THE PAST FEW DAYS A FUNCTION OF THE CURRENT UNORGANIZED NATURE OF THE SYSTEM OR OF GRID-SCALE FEEDBACK PROBLEMS IN THE MODEL? LOOKING BACK AT THE LAST 2 DAYS WORTH OF 00Z AND 12Z RUNS OF THE GFS AND ECMWF BEGINNING AT 00Z/21...THE ECMWF IS SHOWING CONSIDERABLY BETTER RUN-TO-RUN CONSISTENCY WITH THE EVOLUTION OF THE LOW PRES SYSTEM IN THE GULF OF MEXICO THAN THE GFS. FOR THE VALID TIME 25/12Z...THESE GFS RUNS VARY AS WIDELY AS A CONSOLIDATED 998 MB LOW NEAR 27N85W TO A MORE STRUNG OUT TROUGH STRETCHED FROM A 1001 MB ATLC LOW NEAR 29N79W THROUGH FL TO 1003 MB LOW PRES NEAR 25N85W AND INTO THE SW GULF. THE NEW 12Z GFS CARRIES THE LOW ACROSS FL BY THIS TIME...WITH A 1003 MB LOW NEAR DAYTONA BEACH. THE ECMWF RUNS VALID AT THE SAME TIME...25/12Z...AGREE ON A LOW CENTER IN THE CENTRAL GULF SOMEWHERE FROM 26N TO 28N BETWEEN 85W AND 91W. THE 21/00Z ECMWF HAS STRAYED FROM THE EARLIER RUNS BY DEEPENING THE SYSTEM MORE RAPIDLY BY THIS TIME. A QUICK GLANCE AT THE NEW 12Z ECMWF SHOWS A SLIGHT WESTWARD TREND THROUGH SUN. UNFORTUNATELY...THE NEW 12Z NOGAPS...CMC...GFS...AND UKMET ARE SHOWING MORE SPREAD IN THEIR SOLUTIONS THAN THE RUNS AVAILABLE THIS MORNING. BY 25/12Z THE NOGAPS AND UKMET ARE IN THE W GULF AND THE CMC IS IN THE N CENTRAL GULF WITH ONLY THE GFS STRUNG OUT ACROSS FL. WHILE CONFIDENCE IS LOW IN THE FLIP-FLOPPING GFS...ITS TOUGH TO COUNT OUT THE IDEA OF ENERGY SHEARING NE ALONG THE UPPER TROUGH PASSING N OF THE LOW. THIS FORECAST SCENARIO WAS AGREED UPON BY NHC AND HPC DURING THE MEDR CONCALL. THE 06Z GEFS MEAN HOLDS THE PRIMARY SURFACE LOW IN THE GULF...BUT ALLOWS ENERGY TO PASS NE INTO THE SW N ATLC WITH WINDS AND SEAS INCREASING THERE BEGINNING SUN NIGHT. THIS WAS THE PREFERRED SOLN FOR THE PREVIOUS FORECAST PACKAGE. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... SEE THE SECTION ABOVE FOR THE FORECAST REASONING FOR THE SYSTEM IN THE GULF OF MEXICO WHICH WILL CONTROL THE STRENGTH AND POSITION OF THE SUBTROPICAL RIDGE N OF THE CARIBBEAN/TROPICAL N ATLC THAT WILL DRIVE THE TRADE WINDS. FRESH LOW LEVEL SOUTHERLY FLOW IN THE NW CARIBBEAN ON THE W SIDE OF THE RIDGE IS PUMPING MOISTURE TOWARD THE SURFACE TROUGH IN THE GULF OF MEXICO. NUMEROUS TSTMS CURRENTLY LIE OVER THE YUCATAN CHANNEL AND ALONG THE NE COAST OF THE YUCATAN. THE PATTERN WILL CHANGE LITTLE HERE THROUGH THE WEEKEND. BY EARLY NEXT WEEK...THE FORECAST LARGELY DEPENDS ON THE EVOLUTION OF THE SYSTEM IN THE GULF OF MEXICO. THE PREFERRED 06Z GEFS MEAN KEEPS THE SOUTHERLY FLOW FRESH IN THE NW CARIBBEAN THROUGH MON. FRESH WINDS ELSEWHERE SHOULD BE CONFINED TO THE CENTRAL CARIBBEAN. A WEAK TROPICAL WAVE IS EXPECTED TO PASS INTO THE TROPICAL N ATLC AREA SUN AND INTO THE CARIBBEAN MON. THE ONLY IMPACT ON THE SENSIBLE WX SHUD BE A MODEST INCREASE IN SHOWERS AND TSTMS NEAR THE WAVE. SOUTHWEST NORTH ATLC S OF 31N W OF 55W... THE UPPER LOW NE OF THE BAHAMAS IS EXPECTED TO REMAIN STATIONARY AND GRADUALLY WEAKEN THROUGH SAT MORNING BEFORE BEING PUSHED NE BY A PASSING UPPER TROUGH OVER THE WEEKEND. THIS UPPER TROUGH IS ALSO FORECAST BY SOME OF THE MODELS TO CARRY ENERGY FROM THE GULF OF MEXICO LOW NORTHEASTWARD INTO NW WATERS OVER THE WEEKEND. PLEASE SEE THE GULF OF MEXICO SECTION ABOVE FOR DETAILS ON THE PREFERRED MODEL HERE...THE 06Z GEFS. THE RESULTING FORECAST KEEPS THE PRIMARY SYSTEM IN THE GULF THROUGH THE FORECAST PERIOD BUT ALLOWS FOR A STRENGTHENING PRES GRADIENT OVER AND N OF THE BAHAMAS BY LATE SUN. THIS SOLN IS MUCH WEAKER THAN THE 12Z GFS WHICH GENERATES GALE FORCE WINDS N OF THE BAHAMAS BY MON MORNING THAT APPEAR TO BE ASSOCIATED WITH SIGNIFICANT GRID-SCALE FEEDBACK. NOTE...GRIDDED MARINE OUTPUT IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE (LOWER CASE) GULF OF MEXICO... .NONE. CARIBBEAN SEA... .NONE. SW N ATLANTIC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER