000 AGXX40 KNHC 250618 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 215 AM EDT SAT AUG 25 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... THE PRELIMINARY 06 UTC SURFACE ANALYSIS HAS A RIDGE EXTENDING FROM THE SE U.S. SW TO TO THE SW PORTION OF THE GULF. A DEEP LAYER TROUGH STRETCHES FROM THE ERN U.S. SW TO THE ERN GULF AT 23N89W. BUOYS AND OIL RIG PLATFORMS ARE REPORTING GENERALLY NE-E WINDS OF 10-15 KT S OF THE RIDGE...AND E-SE 10-15 KT N OF THE RIDGE...EXCEPT SE-S 5 KT IN THE FAR NE PORTION. REPORTED SEAS HEIGHT VALUES ARE IN THE 2-4 FT RANGE...EXCEPT 1-2 FT N OF 26N E OF 89W. THESE VALUES ARE CLOSE TO THE NOAA WAVEWATCH III GUIDANCE HEIGHTS. WILL USE GUIDANCE FOR MOST OF THE FORECAST PERIOD. UPCOMING SIGNIFICANT CHANGES TO WINDS AND SEAS WILL BE ATTRIBUTED TO TROPICAL STORM ISAAC CURRENTLY TRACKING NW ACROSS CENTRAL CARIBBEAN NEAR SW HAITI. ISAAC IS FORECAST TO MOVE ALONG THE N CENTRAL COAST OF CUBA AND ACROSS THE STRAITS OF FLORIDA SUN WHILE INTENSIFYING...REACHING TO NEAR 24.9N 81.6W BY SUN EVENING. THE PRES GRADIENT IS ALREADY TIGHTENING OVER THE SE GULF IN RESPONSE TO THE APPROACH OF ISAAC. SEAS WILL BUILD TO THE 10-14 FT RANGE ON SUN IN THE SE GULF...AND TO AROUND 20 FT BY SUN NIGHT. THE LATEST NHC ADVISORY VALID 0300 UTC AUG 25 FORECASTS ISAAC TO STRENGTHEN INTO TO A MINIMAL HURRICANE NEAR 27N85W MON NIGHT WITH MAXIMUM WINDS OF 70 KT GUSTS TO 80 KT...AND TO NEAR 30.0N 86.5W EARLY TUE EVENING. ISAAC WILL HAVE A SIGNIFICANT IMPACT ON WINDS AND SEAS OVER MUCH OF THE ERN AND MIDDLE GULF WATERS THROUGH THE FORECAST PERIOD. ASSOCIATED SEAS WILL VARY GREATLY IN IN ITS PERIPHERY AS WELL WITH SWELLS RADIATING OUTWARD INTO MOST OF THE MIDDLE PORTION OF THE GULF. I AM LEANING ON USING THE NORTH ATLANTIC HURRICANE (NAH) WAVEWATCH GUIDANCE FOR SEAS RELATED TO ISAAC AS THE CONVENTIONAL WAVEWATCH MODEL SEEMS ABOUT 3-4 FT TOO LOW INTO EARLY MON...AND ABOUT 4 FT TOO LOW THEREAFTER THROUGH WED. SOUTHWEST NORTH ATLC S OF 31N W OF 65W... THE PRELIMINARY 06 UTC SURFACE ANALYSIS HAS A RIDGE EXTENDING SW OVER THE FAR NW WATERS. BUOYS ARE CURRENTLY REPORTING WINDS OF 10-15 KT OVER MUCH OF THE AREA...WITH THE EXCEPTION OF 26N W OF 69W WHERE MUCH HIGHER WINDS DUE TO THE TIGHT PRES GRADIENT ASSOCIATED WITH TROPICAL STORM ISAAC JUST S OF HAITI. AN ASCAT PASS FROM 0242 UTC LAST NIGHT SHOWED MAINLY E WINDS OF 20-30 KT S OF 25N W OF 69W...WITH TROPICAL STORM FORCE WINDS ON THE EASTERN EDGE OF THE SWATH S OF 22N BETWEEN 70W AND 73W. BUOYS AND A FEW SHIP OBSERVATIONS INDICATE THAT SEAS ARE BUILDING ACROSS MOST OF THE AREA. SEAS OF 6-8 FT IN MAINLY A SE SWELL ARE EVIDENT S OF 28N E OF 75W...WITH MUCH HIGHER SEAS OF 10-17 FT S OF 22N BETWEEN 70W AND 75W. LOWER SEAS OF 2-4 FT IN A SE SWELL ARE N OF 28N AND W OF ABOUT 75W. WAVEWATCH GUIDANCES FORECAST SEAS TO CONTINUE TO BUILD OVER THE WRN PORTION OF THE AREA INTO MON...DUE TO THE STRONG ELY FETCH WITH GIVEN LONG ENOUGH DURATION TO THE N OF ISAAC EVEN THROUGH ISAAC MOVES INTO THE GULF OF MEXICO SUN NIGHT. THESE SEAS WILL THEN SLOWLY SUBSIDE THROUGH WED AT WHICH TIME LINGERING SE SWELLS OF AROUND 6-8 FT MAY STILL BE FOUND IN THE NW PART OF THE AREA. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... TROPICAL STORM ISAAC WAS CENTERED NEAR 18.0N 72.8W AT 2 AM EDT WITH MAXIMUM SUSTAINED WINDS 60 KT GUSTS TO 75 KT. THE MINIMUM CENTRAL PRESSURE WAS 990 MB...WITH A FORWARD MOTION TO THE NW OR 310 DEG AT 12 KT. ISSAC HAS A BROAD CIRCULATION THAT CONSISTS OF RAINBANDS WITH INCREASING CONVECTION FROM 13N TO 18N AND BETWEEN 66W AND 76W. THE ASCAT PASS FROM 0240 UTC LAST NIGHT CAPTURED THE SW TO W INFLOW INTO THE SW QUADRANT OF ISAAC...AND NE-E 30-35 KT WINDS IN THE N QUADRANT. BUOY 42059 AT 15N67W IS REPORTING 8-10 FT SEAS IN A N SWELL. BASED ON THE LATEST NHC ADVISORY FROM 0300 UTC AUG 25...ISAAC IS FORECAST TO WEAKEN SLIGHTLY AS IT CROSSES SW HAITI IN A FEW HOURS ...THEN ACROSS THE WINDWARD PASSAGE NEAR 19.4N 74.1W AT 12 UTC. ISAAC IS THEN FORECAST TO CONTINUE A NW MOTION ALONG THE N CENTRAL CUBAN COAST THROUGH TONIGHT...AND ACROSS THE THE STRAITS OF FLORIDA SUN AS IT BEGINS TO INTENSIFY. ISAAC IS FORECAST TO CONTINUE TO INTENSIFY AS MOVES FURTHER NW AND INTO THE SE GULF SUN NIGHT. THE HIGHEST SEAS WILL REMAIN IN THE N SEMICIRCLE OUTSIDE OF THE IMMEDIATE CARIBBEAN...WITH LARGE SWELLS IMPACTING THE NE-E FACING SIDES OF THE ISLANDS. SOME OF THIS SWELL WILL MANAGE TO BLEED THROUGH THE ATLC PASSAGES. WILL REFLECT THIS ON THE NEXT SET OF PUBLISHED GFE GRID DATA. THE CENTRAL AND WESTERN PORTION OF THE CARIBBEAN WILL BE UNDER THE INFLUENCE OF THE LARGE CIRCULATION ASSOCIATED WITH ISAAC THROUGH EARLY MON...AT WHICH TIME IT WILL BE IMPACTING THE NW PORTION OF THE SEA. SEAS OF 8-10 FT IN A N TO NE SWELL WILL BRIEFLY SUBSIDE SUN AFTERNOON...BUT THEN MATERIALIZE AGAIN MON THROUGH WED WHILE MIGRATING WWD. NE-E WINDS OF 10 KT WILL CONTINUE ACROSS THE TROPICAL N ATLC ZONES N OF ABOUT 12N...WHILE E-SE WINDS OF 10 KT WILL REMAIN S OF 12N. SEAS OF 3-5 FT IN A NE TO E SWELL THROUGH TUE NIGHT BEFORE BECOMING MORE LIKE 2-4 FT BY WED. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE GULF OF MEXICO... .TROPICAL STORM WARNING...GMZ021. CARIBBEAN SEA... .TROPICAL STORM WARNING...AMZ015...AMZ021 E OF 75W AND AMZ013 E OF 78W. SW N ATLANTIC... .TROPICAL STORM WARNING...AMZ117 AND AMZ123. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER AGUIRRE