000 AGXX40 KNHC 140652 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 255 AM EDT SUN AUG 14 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 BUT IS EXPECTED TO DISSIPATE TONIGHT. THE WAVE HAS BROUGHT SOME SCATTERED MODERATE CONVECTION TO THE EASTERN BAY OF CAMPECHE AND WILL CONTINUE TO INCREASE THE CHANCE OF PRECIPITATION OVER THE SW GULF THROUGH TONIGHT...BUT IT 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 SUN THROUGH TUE AND DISSIPATE IN PLACE WED AS HIGH PRES SHIFTS INTO THE NW GULF WED AND THU. WINDS WILL REMAIN BELOW A MODERATE BREEZE ACROSS THE ENTIRE GULF THROUGH THU. CARIBBEAN SEA... WINDS IN THE CARIBBEAN ARE MAINLY DRIVEN BY THE PRESSURE GRADIENT BETWEEN THE 1018 MB HIGH PRES SYSTEM NEAR 27N68W AND LOWER PRESSURE OVER SOUTH AMERICA. THIS GRADIENT WILL MAINTAIN FRESH TO STRONG TRADES MAINLY OVER THE S CENTRAL AND SW CARIBBEAN TODAY AND DIMINISH TONIGHT AS THE RIDGE WEAKENS DUE TO T.D. SEVEN AND ANOTHER LOW NEAR 22N57W IMPINGING UPON IT FROM THE EAST. THIS WILL WEAKEN THE PRESSURE GRADIENT OVER THE CARIBBEAN WITH MODERATE TO FRESH TRADES PREVAILING THROUGH TUE. THE FORECAST BECOMES MORE UNCERTAIN LATE TUE THROUGH THU AS THE TROPICAL WAVE CURRENTLY ALONG 40W MOVES INTO THE AREA. THE FORECAST GUIDANCE HAS BACKED OFF ON THE STRENGTH OF THIS SYSTEM AS IT MOVES INTO THE CARIBBEAN. THIS SEEMS REASONABLE GIVEN THE LACK OF CONVECTION OR CLOSED LOW-LEVEL CIRCULATION CURRENTLY ASSOCIATED WITH THIS WAVE. THE 00Z GFS FORECAST LOOKS REASONABLE. TROPICAL N ATLC W OF 55W... THE LOW PRES SYSTEM NEAR 21.5N 56.5W AT 00Z HAS SLOWED ITS FORWARD SPEED TO A STILL FAST 20 KT. THIS SYSTEM WILL BE OUT OF THE TROPICAL N ATLC ZONE LATER THIS MORNING AND IS EXPECTED TO TURN MORE NORTHWARD AS IT MOVES AWAY FROM THE AREA AND STRENGTHENS...POSSIBLY TO A TROPICAL CYCLONE. MEANWHILE...THE MODELS HAVE BACKED OFF ON THE POTENTIAL DEVELOPMENT OF THE TROPICAL WAVE CURRENTLY ALONG 40W. THE MODELS ARE IN BETTER AGREEMENT THIS MORNING ON THE TIMING OF THE SYSTEM AS IT PASSES INTO THE TROPICAL N ATLC ZONE MON NIGHT AND THROUGH THE ISLANDS LATE TUE. REGARDLESS OF THE DEVELOPMENT OF A CLOSED CIRCULATION...THE WIND FIELD ON THE NORTHERN EDGE OF THE SYSTEM SHOULD EXPAND AS IT MOVES INTO THE ZONE DUE TO THE INCREASED PRES GRADIENT BETWEEN THIS SYSTEM AND THE SW MIGRATING SUBTROPICAL HIGH IN THE CENTRAL ATLC. THE FORECAST WILL BE ADJUSTED TOWARD THE 00Z GFS. SOUTHWEST N ATLC... THE CURRENT PATTERN SPORTS A 1018 MB HIGH PRES IS POSITIONED NEAR 27N68W AND A WEAKENED DEEP LAYER TROUGH JUST OFF THE SE U.S. COAST THAT IS EXPECTED TO AMPLIFY THROUGH TUE. NEWLY-FORMED T.D. SEVEN AND 1013 MB LOW PRES NEAR 21.5N 56.5W WILL IMPINGE ON THE HIGH FROM THE EAST. THE HIGH WILL DISSIPATE AS IT SHIFTS NE TODAY. T.D. SEVEN IS FORECAST TO COME WITHIN 75 NM OF THE NE CORNER OF THE AREA TONIGHT...BRINGING FRESH TO STRONG WINDS TO THE NE CORNER LATER TODAY THROUGH EARLY MON MORNING...BUT THE STRONGEST WINDS ARE EXPECTED TO LIE IN THE E SEMICIRCLE WHERE THE PRES GRADIENT IS HIGHEST BETWEEN IT AND THE SUBTROPICAL HIGH. ELSEWHERE...EXPECT LIGHT TO MODERATE WINDS AND FAIRLY TRANQUIL SEAS TODAY WITH THE EXCEPTION OF SE WATERS WHERE A WESTWARD MOVING INVERTED TROUGH WILL GENERATE SOME FRESH WINDS. THIS INVERTED TROUGH WILL CONTINUE W THROUGH S WATERS THROUGH THU WITH SOME MODERATE TO FRESH S TO SE WINDS EXPECTED ON THE BACKSIDE OF THE TROUGH...BUT PRECIPITATION WILL BE ITS MAIN SENSIBLE WX IMPACT. ANOTHER AREA OF LOW PRES...A POSSIBLE TROPICAL CYCLONE IN THE NEXT 48 HOURS...IS EXPECTED TO APPROACH THE NE PORTION MON NIGHT. CONFIDENCE IS VERY LOW ON THE STRENGTH OR TRACK OF THE SYSTEM BY THAT TIME. IT IS EXPECTED TO BE STEERED NORTHWARD BY THE WEAK COLD FRONT MOVING OFF THE NE FL COAST MON AND TUE. THE GFS IS ONE OF THE FEW MODELS THAT DISTINGUISHES THIS SYSTEM FROM T.D. SEVEN AND HAS A SLOWER SOLUTION THAN THE MODEL CONSENSUS BECAUSE IT DOES NOT COMBINE THE SYSTEMS. THE 00Z GFS SEEMS REASONABLE WITH THE TRACK OF THE SYSTEM. AGAIN...THE STRONGEST WINDS WILL REMAIN E OF THE SYSTEM AND AWAY FROM THE ZONE. THE RIDGE WILL BUILD ALONG 29N IN THE WAKE OF THIS SYSTEM ON WED. MODERATE SW WINDS ARE EXPECTED AHEAD OF THE WEAK COLD FRONT EARLY MON THROUGH TUE NIGHT. 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