000 AGXX40 KNHC 150659 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 300 AM EDT MON AUG 15 2011 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 WEAK NW TO SE ORIENTED RIDGE OF HIGH PRESSURE WILL PREVAIL ACROSS THE GULF OF MEXICO THROUGH MUCH OF THE FORECAST PERIOD. A WEAK TROPICAL WAVE IS CURRENTLY PASSING THROUGH THE SW GULF IS ASSOCIATED WITH SCATTERED MODERATE CONVECTION OVER THE BAY OF CAMPECHE THAT SHOULD DISSIPATE BY TONIGHT. THE WAVE WILL HAVE LITTLE IMPACT ON THE WINDS OR SEAS. A WEAK TROUGH OVER THE SE U.S. WILL SLOWLY SETTLE SOUTHWARD INTO THE NE GULF TODAY THROUGH TUE AND DISSIPATE IN PLACE WED AS HIGH PRES SHIFTS INTO THE NW GULF WED AND THU AND MIGRATES E ON FRI. ASIDE FROM DIURNALLY DRIVEN FRESH NE WINDS OFF THE W COAST OF THE YUCATAN...WINDS WILL REMAIN AT OR BELOW A MODERATE BREEZE ACROSS THE ENTIRE GULF THROUGH FRI. CARIBBEAN SEA... THE AREA OF FRESH TRADE WINDS IN THE CARIBBEAN HAS SHRUNK OVER THE LAST 24 HOURS AS THE RIDGE OVER THE SW N ATLC WEAKENED DUE TO T.S. GERT AND A WEAKENING LOW NEAR 25N61W IMPINGING ON IT FROM THE EAST. MODERATE TO FRESH TRADES WILL PREVAIL MON. THE FORECAST BECOMES MORE UNCERTAIN LATE MON THROUGH FRI AS THE TROPICAL WAVE ALONG 52W AT 00Z MOVES INTO THE AREA. THE FORECAST GUIDANCE HAS BACKED OFF ON THE STRENGTH OF THIS SYSTEM OVER THE PAST FEW DAYS. THIS SEEMS REASONABLE GIVEN THE LACK OF CONVECTION OR CLOSED LOW-LEVEL CIRCULATION CURRENTLY ASSOCIATED WITH THIS WAVE. THE 00Z GFS...UKMET...AND ECMWF AREA IN REASONABLE AGREEMENT ON THE TIMING OF THE WAVE AND SHOW PRIMARILY FRESH WINDS...WIND STRONG WINDS MOSTLY CONFINED TO NEAR THE S COAST OF HISPANIOLA AS THE WAVE PASSES BY. TROPICAL N ATLC W OF 55W... THE WEAK TROPICAL WAVE ALONG 52W AT 00Z HAS RACED W OVER THE LAST 24 HOURS AT 25 KT. THE MODELS HAVE BEEN TOO SLOW WITH THIS WAVE. PAST RUNS HAVE TRIED TO DEVELOP THIS SYSTEM...BUT THE CURRENT BATCH OF 00Z FORECAST MODELS ARE MORE IN LINE WITH WHAT IS SEEN IN OBSERVATIONS - A WEAK WAVE WITH LITTLE DEEP CONVECTION AND WINDS BARELY TO ADVISORY CRITERIA. THE GUIDANCE STILL SUGGESTS THAT THE AREA OF FRESH WINDS ON THE NORTHERN EDGE OF THE SYSTEM SHOULD EXPAND MON NIGHT AS THE WAVE BEGINS TO EXIT THE ZONE DUE TO THE INCREASED PRES GRADIENT BETWEEN THIS SYSTEM AND THE SUBTROPICAL HIGH IN THE CENTRAL ATLC THAT IS EXPECTED TO EXPAND EASTWARD AS T.S. GERT AND THE WEAKENING LOW PRES SYSTEM TRAILING IT PASS N. WINDS AND SEAS WILL GRADUALLY SUBSIDE THROUGH FRI BEHIND THE WAVE. SOUTHWEST N ATLC... THE RIDGE OVER THE SW N ATLC HAS BEEN WEAKENED DUE TO T.S. GERT AND A WEAK LOW NEAR 25N61W AT 00Z IMPINGING UPON IT FROM THE EAST. THE 00Z PATTERN SPORTS A 1014 MB HIGH PRES SYSTEM POSITIONED NEAR 27N70W AND A DEEP LAYER TROUGH JUST OFF THE SE U.S. COAST THAT IS EXPECTED TO AMPLIFY THROUGH TUE. GERT IS CURRENTLY ABOUT 80-90 NM E OF THE NE CORNER OF THE AREA BUT WILL CONTINUE N AWAY FROM THE AREA TODAY. FRESH WINDS IN THE NE CORNER WILL DISSIPATE EARLY THIS MORNING WITH THE STRONGEST WINDS LYING IN THE E SEMICIRCLE WHERE THE PRES GRADIENT IS HIGHEST BETWEEN IT AND THE SUBTROPICAL HIGH. THE 0040 UTC ASCAT PASS CAPTURED THE AREA OUTSIDE OF 60 NM EASTERN SEMICIRCLE AND SHOWED WINDS TO 30 KT WITH THE AREA OF WINDS 25 KT OR HIGHER EXTENDING AS FAR AS 240 NM SE QUADRANT. THIS ELONGATED WIND FIELD IS DUE TO THE WEAK LOW PRES SYSTEM TRAILING GERT. HIGH PRES WILL GRADUALLY BUILD S OF GERT AND THIS WEAKENING LOW THROUGH EARLY WED...WITH MODERATE TO FRESH TRADES BUILDING OVER S WATERS WED THROUGH FRI. MEANWHILE...AN INVERTED TROUGH CURRENTLY OVER SE WATERS WILL CONTINUE W-NW THROUGH S WATERS THROUGH WED WITH SOME MODERATE TO FRESH S TO SE WINDS EXPECTED ON THE BACKSIDE OF THE TROUGH. THE MID LEVEL ENERGY ASSOCIATED WITH THE TROF WILL MOVE INTO THE LEADING EDGE OF THE DEEP LAYER TROUGH OVER THE SE U.S. COAST BY THU. WARNINGS... GULF OF MEXICO... .NONE. CARIBBEAN AND TROPICAL N ATLC... .NONE. SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER