000 AGXX40 KNHC 290757 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 357 AM EDT WED AUG 29 2012 UPDATED INITIAL AND FORECAST POSITIONS OF TROPICAL STORM ISAAC AS REFLECTED IN THE LATEST NHC ADVISORY VALID 0900 UTC 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... AT 0700 UTC...HURRICANE ISAAC REMAINED NEARLY STATIONARY NEAR THE COAST OF SOUTHEAST LOUISIANA NEAR 29.0N 90.0W. MINIMUM CENTRAL PRES WAS 968 MB WITH WINDS NEAR 70 KT WITH HIGHER GUSTS. BUOY AND CMAN DATA FROM THE N CENTRAL GULF CONTINUED TO SHOW TROPICAL STORM FORCE WINDS MAINLY N OF 28N BETWEEN 87W AND 92W. MAXIMUM SEAS ARE ESTIMATED TO APPROACH 25 FT OUTSIDE THE SHOALS OF THE MISSISSIPPI SOUND ON THE STRONG EAST SIDE OF ISSAC. BUOY DATA FROM ELSEWHERE ACROSS THE N CENTRAL AND NE GULF OUTSIDE THE AREA OF TROPICAL STORM FORCE WINDS SHOW SEAS OF 13 FT. THE CENTER OF ISAAC WILL CONTINUE MOVING NEAR OR OVER THE SOUTHEASTERN COAST OF LOUISIANA THIS MORNING...AND MOVE INLAND OVER SOUTHEASTERN LOUISIANA DURING THE NEXT DAY OR SO. THE IMPACT OF ISAAC ON THE MARINE WATERS OVER THE GULF WILL START TO DIMINISH THU...AS A RIDGE OF HIGH PRES BUILDS FROM THE NE GULF THROUGH THE CENTRAL MEXICAN COAST. GLOBAL MODELS ARE IN GOOD AGREEMENT MAINTAINING E TO SE WINDS OF 15 TO 20 KT ACROSS THE WESTERN GULF OF MEXICO BY LATE FRI IN THE WAKE OF ISAAC...AND SHOWING THESE WINDS DIMINISHING SAT AND SUN AS THE RIDGE BECOMES MORE ESTABLISHED ACROSS NORTHERN GULF WATERS. WAVEWATCH GUIDANCE SHOWS SEAS OFF THE LOUISIANA COAST DROPPING FROM 13 FT EARLY THU LARGELY WITH SOUTHERLY SWELL...TO 8 FT BY EARLY FRI AS SWELL DECAYS AND WINDS DIMINISH. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... ASCAT DATA FROM AROUND 03 UTC INDICATED NE TO E TRADE WINDS AROUND 20 TO 25 KT OFF THE COAST OF COLOMBIA. LITTLE WILL CHANGE THROUGH SAT ACROSS THE CARIBBEAN AS A RIDGE OF PRES N OF THE AREA MODULATES ONLY SLIGHTLY. THE MAIN ISSUE WILL BE THE TRACK AND DEVELOPMENT OF BROAD LOW PRES CURRENTLY LOCATED WELL EAST OF THE AREA IN THE TROPICAL ATLC ABOUT 550 NM WSW OF THE CAPE VERDE ISLANDS. BOTH GFS AND ECMWF SHOW THIS SYSTEM BECOMING BETTER ORGANIZED AS IT MOVES WNW...REACHING 55W NEAR 18N TO 19N BY LATE SAT. DIFFERENCES REMAIN IN INTENSITY AS IS TYPICAL THIS EARLY ON. BUT SLOW DEVELOPMENT CAN BE EXPECTED...AND CURRENT MODEL CONSENSUS TAKE THE LOW TO ABOUT 300 NM NE OF THE LEEWARD ISLANDS BY LATE SUN. THE RIDGE N OF THE AREA WILL WEAKEN IN ADVANCE OF THE APPROACHING LOW...ALLOWING TRADES TO DIMINISH SLIGHTLY BY SUN AND MON. SOUTHWEST NORTH ATLC S OF 31N W OF 65W... 1020 MB HIGH PRES IS CENTERED NEAR 26N64W...WITH A RIDGE EXTENDING W ALONG 26N TO THE NORTH OF THE BAHAMAS AND INTO CENTRAL FLORIDA. BUOY AND SCATTEROMETER DATA SHOW LIGHT TO MODERATE PREVAIL ACROSS THE REGION. THE HIGH PRES WILL WEAKEN AND SHIFT NE AHEAD OF A WEAK FRONTAL BOUNDARY THAT WILL BARELY PUSH S OF 31N BY TONIGHT...BEFORE STALLING AND DISSIPATING ALONG 30N BY LATE THU. A WEAK PRES PATTERN WILL FOLLOW THROUGH THE WEEKEND...MAINTAINING GENERALLY LIGHT TO MODERATE FLOW...MOSTLY EASTERLY THROUGH SUN. THE MAIN ISSUE LATE IN THE PERIOD WILL BE THE APPROACH OF A LOW PRES AREA NOW CENTERED IN THE TROPICAL EASTERN ATLC. MODEL GUIDANCE IN IS FAIRLY GOOD AGREEMENT THROUGH SAT SHOWING THE LOW DEVELOPING AND MOVING WNW...BUT DEEP DISAGREEMENTS IN THE MODEL PERSIST SUN AND MON IN TERMS OF BOTH INTENSITY AND TRACK WITH REGARD TO THIS LOW. THE GFS REMAINS THE MOST BULLISH...AND BRINGS THE LOW TO 24N58W BY LATE MON...BUT THE MUCH WEAKER EUROPEAN RECURVES THE LOW TO THE N CENTRAL ATLC MORE QUICKLY. NO IMPACT AS THIS POINT ON THE FORECAST FOR MON AT LEAST W OF 65W. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE GULF OF MEXICO... .TROPICAL STORM WARNING...GMZ013 THROUGH TONIGHT AND GMZ015 THROUGH TODAY. CARIBBEAN SEA... .NONE.. SW N ATLANTIC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER CHRISTENSEN