000 AGXX40 KNHC 210644 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 245 AM EDT MON SEP 21 2009 GULF OF MEXICO... A NE TO SW RIDGE ACROSS NORTHERN GULF IS EXPECTED TO PERSIST THROUGH TUE MORNING...THEN THE RIDGE RETRACTS NE ALLOWING A WEAKENING COLD FRONT TO REACH THE TX COASTAL PLAINS AROUND SUNSET TUE AND JUST OFFSHORE EARLY WED. THE FRONT SHOULD STALL IMMEDIATELY OVER THE NW WATERS WHILE CONTINUING EASTWARD ACROSS THE N CENTRAL COASTAL PLAINS...PERHAPS POKING JUST OFFSHORE THE MS DELTA BEFORE STALLING AND GRADUALLY WASHING OUT THU INTO FRI. MODELS ARE NOT AS AGGRESSIVE WITH NLY FLOW IMMEDIATELY BEHIND FRONT AND ONLY EXPECT ABOUT 10 KT. IN THE MEANTIME THE REMNANT TROUGH OF TC FRED WILL SPLIT WITH THE SOUTHERN SEGMENT OF TROUGH REACHING THE SE FL COAST AND STRAITS OF FL AROUND SUNSET TUE... AND MOVING W OVER THE SE GULF WATERS WED...BECOMING A BROAD INVERTED TROUGH OVER THE SOUTHERN WATERS THROUGH THE REMAINDER OF THE WEEK. ALTHOUGH SEEMS LIKE MOST OF THE MOISTURE FORMALLY ALONG THIS TROUGH HAS LIFTED OUT TO N OVER THE ATLC THERE WILL CERTAINLY BE AN INCREASE IN PRECIP OVER THE SOUTHERN GULF WHERE THE LOW LEVEL IS ALREADY BACKED FROM E TO NE WITH THE APPROACHING TROUGH NEARLY 400 NM TO THE E. AS THE FRONT DISSIPATES...HIGH PRES FROM THE N WILL BRIDGE THE FRONTAL REMNANTS...AND COMBINED WITH THE BROAD LOW PRES OVER THE SOUTHERN PORTION...THE GRADIENT WILL INCREASE THE NE FLOW TO 15 KT ACROSS MOST OF THE CENTRAL WATERS WITH 15-20 KT W OF THE TROUGH ALONG 22N TUE NIGHT INTO WED. THE GRADIENT WILL RELAX THROUGHOUT ON FRI. SW N ATLC... ALOFT...A DEEP LAYERED TROUGH HAS SWUNG S OVER THE N CENTRAL PORTION. AN UPPER RIDGE HAS AMPLIFIED E ACROSS FL TO A FAIRLY SHARP CREST NEAR 27N70W. A CENTRAL ATLC TUTT EXTENDS SW THROUGH UPPER CYCLONES AT 28N45W...24N60W AND 19N63W. AT THE LOW LEVELS THE REMNANT LOW OF TC FRED IS NEAR 30N72W AND HAS WEAKENED TO 1017 MB. THE MOISTURE THAT ACCOMPANIED THIS LOW HAS ADVECTED NE WITH THE LOW AND IS NOW INTERACTING WITH THE UPPER TROUGH WITH CONVECTION ENHANCED NEAR 31N78W. EXPECT THIS LOW TO FILL AND THE ASSOCIATED TROUGH THAT CURRENTLY EXTENDS S FROM THE LOW TO HISPANIOLA TO CONTINUE TO TRACK NW TO ALONG 77W-78W LATE MON INTO MON NIGHT. THEREAFTER...THE TROUGH SPLITS WITH THE NORTHERN SEGMENT CONTINUING NW TO THE GA/SC COAST WED. THE SOUTHERN BRANCH OF THE TROUGH SHOULD MOVE W THROUGH THE STRAITS OF FL TUE TO ALONG THE SE FL COAST AT SUNSET TUE. EXPECT THE NE TO SW ORIENTATED TROUGH TO CONTINUE W BECOMING A BROAD INVERTED TROUGH DOMINATING THE SE GULF THROUGH WED NIGHT...THEN THE CONDITIONS SHIFT W OVER THE S CENTRAL GULF. THE LOW LEVEL FLOW HAS ALREADY BACKED TO NE OVER THE AREA S OF 27N W OF 76W. AS THESE TROUGHS MOVE W OF 80W WEAK HIGH PRES BUILDS ACROSS THE AREA W OF 65W. BETWEEN 65W AND 55W...THE REMNANTS OF ANOTHER TROPICAL LOW NEAR CURRENTLY NEAR 15N47W IS EXPECTED TO STEER INITIALLY NW AND LATER N AND NNE IN RESPONSE TO THE UPPER LOW AT 24N70W. THE GRADIENT N OF THIS LOW HAS A BELT OF ELY 20-25 KT WINDS FROM 18N-26N E OF 60W. THE LOW LEVEL WINDS WILL GRADUALLY BACK TO THE NE AS THE WEAKENING LOW TRACKS N ALONG 53W. CARIBBEAN AND TROPICAL N ATLC... THE UPPER CYCLONE OVER THE NW CARIBBEAN HAS MOVED W OVER BELIZE AND CONTINUES TO WEAKEN...BUT IS STILL KICKING OFF CONVECTION W OF 82W. OTHERWISE 10-15 KT NE-E TRADES COVER MOST OF THE CARIBBEAN BASIN EXCEPT 20-25 KT ALONG COAST OF S AMERICA. ONLY MINOR FLUCTUATIONS IN THIS PATTERN ARE EXPECTED REMAINDER OF THE WEEK WITH THE EXCEPTION THAT AS THE TROPICAL LOW MENTIONED ABOVE PASSES N TO THE E OF 55W...THE ELY TRADES AT 15-20 KT WINDS WILL BECOME LIGHT AND VARIABLE...BASICALLY N OF 18N E OF 60W. ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE $$ FORECASTER NELSON