000 AGXX40 KNHC 201806 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 215 PM EDT FRI APR 20 2012 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... SLY FLOW HAS INCREASED BRIEFLY TO 15-20 KT OVER NW WATERS THIS MORNING AS APPROACHING SHORTWAVE ADVANCES ACROSS CENTRAL TX. THE COLD FRONT...PRECEDED BY A CONVECTIVE SQUALL LINE...WILL SLOWLY ENTER THE NW GULF THIS EVENING...THEN ACCELERATE...REACHING A POSITION FROM THE MISSISSIPPI DELTA TO THE BAY OF CAMPECHE AT SUNRISE SAT AND FROM THE FL BIG BEND TO YUCATAN PENINSULA AT SUNRISE SUN. BY THEN A FRONTAL WAVE LOW WILL HAVE DEVELOPED ALONG THE NORTHERN SEGMENT OF THE FRONT. GUIDANCE DIFFERS SLIGHTLY ON THE LOW POSITION...THUS USED A BLEND OF GFS ENSEMBLE/GFSP/AND ECM TO MOVE THE LOW ACROSS CENTRAL-N FL SAT NIGHT PRECEDED BY A NORTHWARD MOVING CONVECTIVE WARM FRONT. AS THE LOW RACES NE LATE SAT NIGHT INTO EARLY SUN...IT WILL ACCELERATE THE COLD FRONT MOVING IT RAPIDLY SE THROUGH THE FL STRAITS ON SUN AFTERNOON ACCOMPANIED BY ANOTHER ROUND OF TSTMS. FOR NOW...EXPECT THE POST FRONTAL CAA TO MAX AT 30 KT OVER THE CENTRAL GULF WATERS...AS OPPOSED TO THE MAX WINDS NORMALLY DAMMED ALONG THE WESTERN GULF. ASSOCIATED SEAS EXPECTED TO MAX AT 13 FT...ALSO ACROSS THE CENTRAL GULF WATERS. NLY WINDS WILL DIMINISH BELOW 20 KT OVER THE W GULF SUN MORNING...WITH THESE CONDITIONS SPREADING E ACROSS THE REMAINDER OF THE GULF BY NOON TUE. BY THEN...SE RETURN FLOW WILL HAVE SET UP OVER THE NW WATERS...SPREADING E ACROSS ALL GULF WATERS W OF 93W LATE TUE NIGHT. A SURFACE HIGH WILL DROP SE AND BE CENTERED NEAR 28N83W WED WITH A RIDGE W TO SW LA WED AND WED NIGHT...WITH THE SLY FLOW INCREASING TO 15-20 KT OVER THE WESTERN PORTION. SW NORTH ATLC S OF 31N W OF 65W... A RIDGE EXTENDS FROM A SURFACE HIGH JUST SW OF BERMUDA TO CENTRAL FL. SOUTHERLY WINDS N OF THE RIDGE WILL GRADUALLY INCREASE TODAY AND SAT AHEAD OF A STRONG COLD FRONT MOVING OFF THE SE CONUS AT SUNRISE SUN. USING A BLEND OF GFS ENSEMBLE/GFSP AND ECM...WILL MOVE THE FRONT TO A POSITION FROM 31N74W TO CENTRAL CUBA AT SUNRISE MON...THEN WEAKEN THE FRONT AS IT REACHES FROM 31N67W TO W HISPANIOLA LATE TUE...AND FROM BERMUDA TO E HISPANIOLA TUE NIGHT. THE FRONT WILL STALL FROM 31N63W TO THE MONA PASSAGE WED...AND BEGIN TO DRIFT W WED NIGHT. EXPECT SLY FLOW TO MAX AT 30 KT...WITH OCCASIONAL GUSTS TO GALE FORCE...AHEAD OF THE FRONT OVER THE NW WATERS...AND MAX AT 20-25 KT AHEAD OF FRONT AS FAR S AS THE THE BAHAMA CHANNEL. MARINERS BE ADVISED THAT THE SE WINDS WILL BEGIN TO INCREASE TO 15-20 KT IN THE BAHAMA CHANNEL AND THROUGHOUT THE NW BAHAMAS EARLY SAT FURTHER INCREASING TO 20-25 KT SAT AFTERNOON AND CONTINUING TILL THE FROPA SUN NIGHT. THE POST FRONTAL NLY FLOW WILL ACTUALLY DIMINISH THE WINDS OVER THE WATERS S OF 27N...BUT MAINTAIN THE STRENGTH BEHIND THE FRONT FOR AT LEAST 6 HOURS OVER THE NORTHERN WATERS. CARIBBEAN SEA... SE LOW LEVEL FLOW WILL GRADUALLY INCREASE TONIGHT AND SAT OVER THE NW CARIBBEAN AHEAD OF A COLD FRONT MOVING INTO THE YUCATAN CHANNEL LATE SAT. THE FRONT WILL REACH FROM CENTRAL CUBA TO THE GULF OF HONDURAS SUN...THEN WEAKEN AND SLOW AS IT REACHES FROM FROM E CUBA TO NE HONDURAS EARLY MON...AND STALL FROM NEAR THE WINDWARD PASSAGE TO 14N82W TUE...WITH THE REMNANTS DRIFTING W ON WED. EXPECT THE POST FRONTAL NW WINDS TO MAX AT 25 KT OVER THE NW CARIBBEAN SUN NIGHT...THEN GRADUALLY DIMINISH AND CLOCK TO THE NE BY TUE NIGHT. THE NE WINDS WILL INCREASE TO 20-25 KT IN THE WINDWARD PASSAGE AND ACROSS THE NW CARIBBEAN WED NIGHT. OTHERWISE...ELY WINDS WILL REMAIN AT 15 KT OVER THE E AND CENTRAL CARIBBEAN WATERS WITH SEAS TO 7 FT IN THE SW PART...AND GENERALLY SUBSIDING ELSEWHERE. TROPICAL N ATLC S OF 19N W OF 55W... GENERALLY LIGHT E TRADES S OF 17N WILL BECOME FRESH ON SAT AS HIGH PRES STRENGTHENS N OF AREA. NW-N WINDS OF 5-10 KT N OF 17N WILL BECOME NE-E 10-15 KT LATER TODAY. SEAS WILL RANGE FROM 4-6 FT...WITH THE HIGHEST IN THE CENTRAL AND SOUTHERN PORTIONS. 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 AND TROPICAL N ATLC... .NONE. .SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER NELSON