000 AGXX40 KNHC 180635 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 245 AM EDT MON MAR 18 2013 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLC...AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... AN UPPER LEVEL TROUGH PROGRESSING FROM THE CENTRAL GULF TO THE E GULF CONTINUES TO TRIGGER SOME SHOWERS AND ISOLATED TSTMS IN THE NORTHERN AND NE GULF. MODERATE SOUTHERLY RETURN FLOW DOMINATES THE ENTIRE GULF WITH A RIDGE LOCATED ALONG 30N/31N EXTENDING FROM HIGH PRES IN THE ATLC S OF BERMUDA. RETURN FLOW WILL WEAKEN THIS EVENING AS A COLD FRONT APPROACHES THE NW AND N CENTRAL GULF WATERS. THIS FRONT IS FORECAST TO REACH FROM THE FLORIDA BIG BEND TO NEAR BROWNSVILLE TEXAS TUE MORNING...THEN WILL STALL FROM SW FLORIDA TO THE TEXAS/MEXICO BORDER TUE NIGHT. THE FRONT IS NOW FORECAST TO DISSIPATE OVER THIS GENERAL AREA...EXCEPT THE WESTERN PORTION MAY STILL LIFT NORTHWARD AS A WARM FRONT AS LOW PRES DEVELOPS OVER OKLAHOMA AND NORTHERN TEXAS. GFS MODEL GUIDANCE HAS SLOWED WITH THE TIMING OF THE NEXT COLD FRONT ASSOCIATED WITH THIS LOW PRES SYSTEM WITH IT POTENTIALLY IMPACTING THE GULF WATERS BY SAT MORNING VERSUS AN ARRIVAL ON FRI WHICH THE ECMWF STILL SHOWS. CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W... A RECENT ASCAT PASS SHOWED FRESH TO STRONG E-SE WINDS IN THE MAJORITY OF THE GULF OF HONDURAS BETWEEN TROUGHING ALONG THE NW YUCATAN COAST AND RIDGING EXTENDING FROM THE WESTERN ATLC. LITTLE CHANGE IN THESE CONDITIONS IS FORECAST THROUGH EARLY TUE...WITH THE WINDS DIMINISHING BY TUE AFTERNOON. THE STRONGER WINDS MAY RETURN BY THE END OF THE WEEK AS THE PRES GRADIENT TIGHTENS...DEPENDENT ON THE TIMING OF A FRONT N OF THE AREA IN THE GULF OF MEXICO. OTHERWISE...FRESH TO STRONG WINDS ARE IN THE CENTRAL CARIBBEAN WITH RECENT NEAR COASTAL HIGH RESOLUTION ASCAT DATA SHOWING SEVERAL "RED" 30-34 KT WIND BARBS WITHIN 60 NM OF THE COAST OF COLOMBIA. THERE MAY BE A FEW GUSTS TO GALE FORCE BUT GIVEN THE SMALL AREA SO CLOSE TO THE COAST AND WITH FREQUENT GUSTS NOT EXPECTED HAVE OPTED TO NOT RAISE A GALE WARNING AT THIS TIME. THESE WINDS WILL SIGNIFICANTLY DIMINISH TO 20-25 KT ONLY WITHIN 90 NM OF THE COAST OF COLOMBIA TUE AFTERNOON...THEN TO ONLY 15-20 KT LATE WED THROUGH FRI. IN THE TROPICAL N ATLC...AN OLD FRONTAL BOUNDARY HAS EVOLVED INTO A SHEAR LINE AS ADVERTISED IN THE NORTHERN WATERS WITH NE 20 KT WINDS N OF THE BOUNDARY AND 15 KT S OF THE BOUNDARY. THE SHEAR LINE IS FORECAST TO DISSIPATE THIS AFTERNOON INTO THE EVENING. N-NE SWELLS OF 6-8 FT WILL GRADUALLY SUBSIDE THROUGH THE WEEK. SW N ATLC S OF 31N W OF 55W... SCATTERED SHOWERS AND TSTMS ARE BEING ADVECTED AHEAD OF THE UPPER LEVEL TROUGH MENTIONED ABOVE IN THE E GULF OF MEXICO TO THE ATLC WATERS N OF 26N W OF 70W. 1023 MB HIGH PRES IS NEAR 27N65W AS INDICATED BY 0158 UTC ASCAT DATA WITH A RIDGE ALONG 27N. LIGHT TO MODERATE ANTICYCLONIC WINDS DOMINATE THE BASIN. SOUTHERLY WINDS WILL INCREASE IN THE FAR NW PORTION LATE TONIGHT AHEAD OF A COLD FRONT. THE GFS SHOWS FRESH TO STRONG WINDS AHEAD OF AND BEHIND THE FRONT WHILE THE UKMET AND ECMWF SHOW MAINLY MODERATE TO FRESH WINDS. PREFER THE MORE CONSERVATIVE SOLUTIONS FOR NOW AS THE GFS REMAINS THE OUTLIER. THE FRONT WILL REACH FROM 31N75W TO NEAR JUPITER FLORIDA TUE EVENING...THEN FROM BERMUDA TO SE FLORIDA WED AFTERNOON WHERE IT WILL STALL UNTIL A REINFORCING FRONT MERGES/OVERTAKES THE OLD BOUNDARY ON THU. THAT NEW FRONT WILL EXTEND FROM BERMUDA TO THE NORTHERN BAHAMAS THU EVENING...EXITING THE REGION FRI AS HIGH PRES BUILDS IN FROM THE W-NW. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE WARNINGS... GULF OF MEXICO... .NONE. CARIBBEAN SEA AND TROPICAL N ATLC... .NONE. SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER LEWITSKY