000 AGXX40 KNHC 181850 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 250 PM EDT FRI SEP 18 2009 GULF OF MEXICO... DEEP LAYERED CYCLONE PERSISTING ACROSS THE AREA FOR NEARLY A WEEK AND NOW OVER NW LA APPEARS TO BE FILLING...BUT A SERIES OF LOW LEVEL TROUGHS OR WEAK COLD FRONTS WILL CONTINUE ROTATE THROUGH THE PATTERN OVER THE NW GULF. CURRENTLY A WEAK FRONTAL TROUGH IS STALLING AND LOSING IDENTITY FROM THE MS DELTA TO NEAR 25N96W. EXPECT A BROAD WEAK TROUGH TO CONTINUE OVER THE NW GULF THROUGH SUN AND DISSIPATE SUN NIGHT. A BROAD TROUGH WILL DEVELOP OVER THE S CENTRAL GULF LATE IN THE WEEKEND AND CONTINUE INTO MON. EXPECT LIGHT TO MODERATE WINDS 5-15 KT AND SEAS 4 FT OR LESS THE THROUGH WEEKEND. SW N ATLC... A QUASI-STATIONARY TROUGH EXTENDS ALONG FROM 31N72W TO NW BAHAMAS AND THEN BROAD TROFFING TO JUST E OF THE KEYS. THIS TROUGH WILL MEANDER THROUGH TONIGHT AND THEN BECOME STRETCHED NE TO SW...WITH SW PORTION MOVING NW INTO FLORIDA OVER THE WEEKEND. WINDS ON BOTH SIDES OF TROUGH HAVE GENERALLY BEEN 10-15 KT. THE REMNANTS OF TC FRED...A TIGHT LLVL SWIRL IN SATELLITE IMAGERY...WAS ALONG 26N67W THIS AFTERNOON...MOVING NW 15 KT. THE LOW LEVEL TROUGH THAT THIS FEATURE IS EMBEDDED WITHIN IS MOVING WNW AND EXPECTED TO MOVE IN THIS MANNER NEAR 15 KT AND VERY GRADUALLY SLOW...REACHING THE NW BAHAMAS IN 48 HOURS. A MORNING QUICKSCAT PASS STILL SHOWED 20-25 KT WINDS IN N SEMICIRCLE OF THIS SWIRL...WITH SEAS ESTIMATED 8 TO 10 FT WITHIN 240 NM N AND NE. AS THIS MOVES WNW...THE LOW IS EXPECTED TO OPEN UP INTO A MORE OBVIOUS TROUGH...THAT SHOULD MOVE NW REACHING THE SE FL COAST MON. HIGH PRES WILL BUILD ACROSS THE AREA FROM THE E BEHIND THIS TROUGH WITH E-SE WINDS 15 KT AND SOME SMALL AREAS 15-20 KT...BY LATE IN THE PERIOD. CARIBBEAN AND TROPICAL N ATLC... HIGH PRESSURE BUILDING INTO THE SUBTROPICAL ATLANTIC BEHIND FRED AND BETWEEN THE NEXT TROPICAL LOW ALONG 40W HAS PRODUCED A BROAD AREA OF 20-25 KT WINDS...AND 7-8 FT SEAS IN A MIX OF SE AND NE SWELLS. THIS WILL SHIFT SLOWLY W AND WEAKEN BEHIND THE WEAKENING REMNANTS OF FRED...BUT WITH THE NELY SWELL MOVING INTO THE ATLC WATERS AND PASSAGES OF THE CARIBBEAN. THE TROPICAL LOW NEAR 13.5N40W IS EXPECTED TO MOVE WNW FOR THE NEXT FEW DAYS...AND THEN MORE NW INTO THE OPEN W ATLC. THERE IS A MODERATE CHANCE THAT THIS SYSTEM COULD DEVELOP INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. REGARDLESS...THE PRESSURE GRADIENT BETWEEN THIS BROAD LOW AND HIGH PRESSURE TO THE N WILL MAINTAIN A BROAD ZONE OF 20-25 KT WINDS WITHIN SEVERAL DEGREES TO THE N...AND LIKELY 25-30 KT WITHIN 120 NM OF SO OF THE N SEMICIRCLE...AT LEAST WITHIN THE NEXT 48 HOURS. ACROSS THE CARIBBEAN...THE REMNANTS OF FRED AND NEXT THIS TROPICAL LOW HAVE INTERRUPTED FRESH TRADES ACROSS THE ENTIRE CARIBBEAN...LEAVING 10-15 KT FLOW ACROSS THE BASIN TODAY...AND SEAS 3-5 FT...WITH LOCAL EFFECT INDUCING SOME SMALL ISOLATED AREAS NEAR 20 KT. AS HIGH PRESSURE BUILDS BEHIND THE REMNANTS OF FRED...FRESH TRADES WILL RETURN TO THE SRN CARIBBEAN OVER THE WEEKEND...NEAR 20 KT AND SEAS GRADUALLY BUILDING TO NEAR 8 FT...WHILE THE REST OF THE BASIN IS AROUND 15 KT AND SEAS 5 FT OR LESS. THE UPPER LOW ACROSS THE W CARIB WILL CONTINUE TO PRODUCE ACTIVE WEATHER THROUGH 36-48 HOURS. ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE $$ FORECASTER STRIPLING