000 AGXX40 KNHC 301911 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 245 PM EST MON NOV 30 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W GULF OF MEXICO... A STRONG COLD FRONT OVER THE NW GULF HAS BROUGHT 20 TO 25 KT WINDS BEHIND IT ACCORDING TO THE SURFACE OBSERVATIONS IN THE REGION. A SURFACE WAVE WILL DEVELOP ALONG THE BOUNDARY TONIGHT. THE LATEST GFS AND ECMWF SOLUTIONS ARE SUPPORTING A DOUBLE BARRELED AREA OF LOW PRES WITH THE INITIAL LOW BECOMING A WAVE ALONG THE WARM FRONT AS A SECOND SURFACE LOW DEVELOPS TO THE W AND BECOMES THE ANCHOR LOW OVERNIGHT TUE NIGHT. AS THE ANCHOR LOW MOVES INLAND WED MORNING...THE GFS IS AMONG THE FASTER SOLUTIONS TO CARRY THE LOW AND COLD FRONT EASTWARD INTO THE CENTRAL GULF. IT ALSO INTENSIFIES THE LOW 5 MB AS IT MOVES INLAND WED MORNING AND GENERATES A LARGE SWATCH OF 5+ INCHES OF PRECIPITATION FROM SE LOUISIANA INTO SOUTHERN ALABAMA AT THAT TIME. THIS APPEARS TO BE DUE TO CONVECTIVE FEEDBACK ASSOCIATED WITH A PIECE OF SHORTWAVE ENERGY MOVING AHEAD OF THE UPPER LOW TUE NIGHT. ADJUSTMENTS WERE MADE TOWARD A SLOWER SOLUTION WITH THE COLD FRONT THAN THE GFS AND A WEAKER SURFACE LOW...CLOSER TO A GFS/ECMWF CONSENSUS. BOTH THE GFS AND ECMWF SHOW A NORTHERN GULF GALE EVENT WED IN THE SOUTHERLY FLOW AHEAD OF THE FRONT WITH WINDS IN THE STRONGER GFS TO 40 KT AND THE ECMWF TO 35 KT. HOWEVER...THE 1200 UTC GEFS PROBABILITIES OF GALE FORCE WINDS HAVE BACKED OFF COMPARED TO EARLIER RUNS...WITH NO SUPPORT FOR A GALE...AND THE 0900 UTC SREFS SHOW LESS THAN A 20 PERCENT CHANCE OF GALES. WITH THE MODELS AGREEING ON AN INCREASINGLY MORE AMPLIFIED NORTHERN STREAM SURFACE PATTERN WITH A BUILDING HIGH PRES SYSTEM OVER THE CENTRAL N ATLC TUE-THU...BELIEVE THE GRADIENT WILL BE STRONG ENOUGH TO SUPPORT THE GALES SEEN IN THE DETERMINISTIC RUNS. FORECAST CALLS FOR A GALE EVENT TUE AND WED...BUT CONSIDERING THE GFS IS THOUGHT TO BE TOO DEEP WITH THE LOW AND THE ENSEMBLES ARE NOT RESOUNDINGLY SUPPORTING GALES...KEEPING WINDS TO 35 KT. CARIBBEAN AND TROPICAL N ATLC... SURFACE OBSERVATIONS SHOW THAT THE WINDS ARE BEGINNING TO SHIFT MORE SOUTHERLY IN THE NW CARIBBEAN IN ADVANCE OF THE STRONG COLD FRONT IN THE GULF OF MEXICO. THIS FRONT IS EXPECTED TO PUSH THROUGH THE YUCATAN CHANNEL ON THU AND BRING 20 TO 25 KT NE FLOW BEHIND IT BY FRI. FARTHER SOUTH...THE PRES GRADIENT N OF THE COLOMBIAN LOW IS RELATIVELY WEAK DUE TO THE WEAK FRONTAL BOUNDARY STRETCHED OVER THE SOUTHERN SW N ATLC ZONE. THE ASCAT PASS FROM 1440 UTC SHOWS WINDS TO 20 KT FLANKING THE 20 TO 25 KT WINDS IN THE CENTRAL CARIBBEAN PRIMARILY THE COAST OF COLOMBIA. SHIP PDKK HAD 23 KT WINDS AT 1800 UTC NEAR 15N74W. EXPECT THE PATTERN TO REMAIN RELATIVELY STAGNANT HERE OVER THE NEXT FEW DAYS. BY MID WEEK...A MORE AMPLIFIED NORTHERN STREAM PATTERN WITH BUILDING HIGH PRES OVER THE CENTRAL N ATLC SHOULD STRENGTHEN THE PRES GRADIENT OVER THE EASTERN CARIBBEAN AND TROPICAL N ATLC...WITH TRADES BUMPING UP IN THESE REGIONS ABOVE 20 KT. MEANWHILE...THE TROPICAL N ATLC IS SEEING WAVE HEIGHTS ABOVE 8 FT IN THE NW SWELL ASSOCIATED WITH THE FRONT THAT STALLED N OF THE ZONE. MOISTURE CONVERGED AHEAD OF THIS WEAK FRONTAL BOUNDARY HAS ENHANCED CONVECTION NEAR THE NE CARIBBEAN ISLANDS. SW N ATLC... THE 1436 UTC ASCAT PASS SHOWS WINDS PICKING UP TO 15 TO 20 KT OVER NW WATERS IN ADVANCE OF THE NEXT COLD FRONT WHICH IS EXPECTED TO MOVE OFF THE GA COAST OVERNIGHT. THE MODELS ARE IN REASONABLE GOOD AGREEMENT WITH THE FORECAST OF THIS FRONT. THIS BOUNDARY RETREATS NORTH AS A WARM FRONT OVERNIGHT TUE NIGHT AND SOUTHERLY FLOW INCREASES AHEAD OF THE STRONG COLD FRONT IN THE GULF OF MEXICO. SEE THE GULF OF MEXICO SECTION FOR FORECAST THINKING WHICH FAVORS A WEAKER AND SLOWER SOLUTION THAN THE GFS. THE 1200 UTC GEFS AND 0900 UTC SREF SUPPORTS UP TO A 20 PERCENT CHANCE OF GALES IN THE SW N ATLC ZONE IN THE SOUTHERLY FLOW AHEAD OF THE FRONT. THE MODELS ARE TRENDING TOWARD TURNING THE SYSTEM NEGATIVE TILT FARTHER NORTH AND RETREATING THE WINDS FARTHER NORTH AS A RESULT. CONFIDENCE IS LOW...BUT GIVEN THE DETERMINISTIC MODEL SUPPORT...GALES CONTINUE TO BE FORECAST. WARNINGS... ATLC... AMZ088...GALE CONDITIONS EXPECTED OF 29N E OF FRONT TO 70W WED THROUGH THU... CARIBBEAN... .NONE. GULF OF MEXICO... GMZ080 AND GMZ084 AND GMZ086...GALE WARNING N OF 27N BETWEEN 85W AND 91W TUE THROUGH WED... $$ FORECASTER SCHAUER