000 AGXX40 KNHC 210657 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 257 AM EDT TUE AUG 21 2012 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... A MID TO UPPER LEVEL TROUGH STRETCHES FROM SE LOUISIANA TO JUST S OF THE TEXAS/MEXICO BORDER. PLENTIFUL MOISTURE AND UNSTABLE AIR CONTINUES TO BE PUMPED UP AHEAD OF THE TROUGH ACROSS THE MAJORITY OF THE GULF...EXCEPT BEHIND THE TROUGH IN THE FAR NW GULF WHERE DRY AIR AND SUBSIDENCE IS PRESENT. A STATIONARY FRONT IS PARKED OUT ALONG THE NW AND N CENTRAL GULF COAST WITH A SURFACE TROUGH OUT AHEAD OF IT FROM NEAR THE FLORIDA BID BEND TO NEAR 26N95W...COINCIDENT WITH THE MID TO UPPER LEVEL TROUGH. THESE FEATURES ARE FORECAST TO EVENTUALLY SLOWLY SHIFT E-SE THROUGH MID WEEK...DISSIPATING THU AS HIGH PRES BUILDS IN FROM THE NE. A SEPARATE SURFACE TROUGH IS JUST E OF THE MEXICAN COAST FROM NEAR 24N97W TO 19N96W. THIS FEATURE IS FORECAST TO LINGER OVER THE SAME GENERAL AREA THROUGH THU...MOVING INLAND OVER MEXICO FINALLY BY THE END OF THE WEEK AS THE HIGH MENTIONED ABOVE PUSHES IN FROM THE NE. THIS TROUGH HAS A MEDIUM PROBABILITY OF TROPICAL CYCLONE DEVELOPMENT DURING THE NEXT 48 HOURS. ALSO...A TROPICAL WAVE CURRENTLY IN THE NW CARIBBEAN MAY CLIP THE SW GULF AND MERGE WITH THIS TROUGH LATER THIS WEEK. THE HIGH WILL RETREAT TO THE NE FRI AND SAT POTENTIALLY ALLOWING FOR AN AREA OF LOW PRES AND ATTENDANT TROPICAL WAVE CURRENTLY E OF THE CARIBBEAN ISLANDS TO MOVE TOWARD THE SE GULF. THIS LOW HAS A HIGH PROBABILITY OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. IF THIS SCENARIO OCCURS...EXPECT DETERIORATING CONDITIONS (INCREASING WINDS AND SEAS) IN THE SE GULF LATE SAT INTO SUN. AHEAD OF THIS LOW...MAINLY LIGHT TO MODERATE WINDS AND 2-4 FT SEAS WILL DOMINATE THE GULF...EXCEPT IN THE NE GULF WHERE 1-3 FT SEAS WILL PREVAIL. A BLEND OF THE GFS AND ECMWF WAS USED FOR THIS FORECAST PACKAGE ALONG WITH THE PRELIMINARY NHC FORECAST FOR THE LOW THAT MAY IMPACT THE SE GULF THIS WEEKEND. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... A TROPICAL WAVE EXTENDS FROM WESTERN CUBA TO THE GULF OF HONDURAS WITH SCATTERED SHOWERS AND ISOLATED TSTMS ACCOMPANYING IT. FRESH TO STRONG WINDS ARE PRESENT ACROSS THE CENTRAL CARIBBEAN WITH AN AREA OF MODERATE TO FRESH WINDS IN THE W CENTRAL CARIBBEAN S OF JAMAICA IN THE LEE OF THE TROPICAL WAVE. ANOTHER TROPICAL WAVE IS IN THE TROPICAL N ATLC WATERS NEAR 60W AND IT WILL MOVE ACROSS THE E CARIBBEAN ISLANDS LATER TODAY AND THROUGH THE E CARIBBEAN TUE NIGHT...THEN THROUGH THE CENTRAL CARIBBEAN WED NIGHT THROUGH THU NIGHT...AND INTO THE W CARIBBEAN FRI AND SAT. THE FRESH TO STRONG WINDS WILL PERSIST IN THE CENTRAL CARIBBEAN THROUGH WED AND E-SE 20-25 KT WINDS WILL SET UP OVER THE GULF OF HONDURAS LATER TODAY THROUGH LATE WED AS HIGH PRES NE OF THE AREA NOSES INTO THE AREA. AN AREA OF 1007 MB LOW PRES IS E OF THE TROPICAL N ATLC NEAR 15N50.5W WITH A TROPICAL WAVE EXTENDING NORTHWARD FROM THE LOW CENTER TO 21N47W. CONVECTION IS INCREASING NEAR THIS LOW AND IT HAS A VERY HIGH PROBABILITY OF TROPICAL CYCLONE DEVELOPMENT AND IT COULD BECOME A TROPICAL DEPRESSION LATER TODAY. 20-30 KT WINDS ARE ALREADY OCCURRING IN THE NE SEMICIRCLE OF THE LOW WITH A TIGHT PRES GRADIENT IN PLACE BETWEEN THE LOW/TROPICAL WAVE AND HIGH PRES TO THE NW. THIS LOW IS FORECAST TO IMPACT THE E CARIBBEAN WATERS BY EARLY WED AND INTO THE E CARIBBEAN LATE WED AND THU...THEN CENTRAL CARIBBEAN FRI. INTERESTS IN THE CARIBBEAN SHOULD CONTINUE TO MONITOR ANY DEVELOPMENTS OF THIS LOW THROUGH THE WEEK INTO THE WEEKEND. SOUTHWEST NORTH ATLC S OF 31N W OF 55W... 1021 MB HIGH PRES IS POSITIONED NEAR 28N62W WITH A RIDGE AXIS EXTENDING WESTWARD TO N OF THE CENTRAL BAHAMAS. WEAK TROUGHS CONTINUE TO MOVE ACROSS THE NW PORTION OF THE REGION HELPING TO SPARK SCATTERED SHOWERS AND TSTMS. RECENT SCATTEROMETER DATA INDICATES PRIMARILY LIGHT TO MODERATE ANTICYCLONIC WINDS ACROSS THE SW N ATLC. THE EXCEPTION IS ACROSS THE WATERS S OF 22N WHERE EASTERLY 15-20 KT WINDS ARE PRESENT. WINDS WILL INCREASE AND SEAS WILL BUILD BEGINNING IN AMZ125 LATER TODAY...SPREADING W-NW AS A DEVELOPING AREA OF 1007 MB LOW PRES CURRENTLY NEAR 15N50.5W MOVES CLOSER TO THE SOUTHERN WATERS. THIS FEATURE HAS A VERY HIGH PROBABILITY OF TROPICAL CYCLONE DEVELOPMENT AND IT COULD BECOME A TROPICAL DEPRESSION LATER TODAY. THE LOW IS EXPECTED TO IMPACT THE NE CARIBBEAN BY LATE WED...THEN POTENTIALLY THE GREATER ANTILLES BY THE END OF THE WEEK. REGARDLESS OF THE EXACT TRACK...A TIGHT PRES GRADIENT WILL REMAIN OVER THE SOUTHERN WATERS BETWEEN THE HIGH...WHICH WILL BE RETREATING NORTHWARD... AND THE LOW. INTERESTS FROM THE NE CARIBBEAN TO ACROSS THE GREATER ANTILLES...TURKS AND CAICOS...AND THE BAHAMAS SHOULD CONTINUE TO MONITOR ANY DEVELOPMENTS OF THIS LOW THROUGH THE WEEK INTO THE WEEKEND. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE GULF OF MEXICO... .NONE. CARIBBEAN SEA... .NONE. SW N ATLANTIC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER LEWITSKY