000 AGXX40 KNHC 190816 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 345 AM EDT THU MAR 19 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... THE REMNANTS OF AN OLD FRONTAL TROUGH ARE STRUNG OUT NEARLY W TO E ALONG ABOUT 25N TONIGHT...FROM THE CENTRAL GULF ACROSS THE FLORIDA KEYS AND INTO THE SW ATLC. STLT IMAGERY AND CIMSS 850 VORTICITY ANALYSIS SUGGEST TWO LLVL CYCLONIC CIRCULATIONS ALONG THIS OLD BOUNDARY...ONE NEAR 24N91.5 AND ANOTHER NEAR 26N88W. EVENING SCATTEROMETER PASSES INDICATE BROAD INVERTED TROFFING BETWEEN THESE TWO FEATURES...FROM THE YUCATAN NNW TOWARDS SRN LOUISIANA. 15-20 KT FLOW...WITH OCCASIONAL POCKETS OF SOLID 20 KT SHOULD BE EXPECTED AROUND THE N AND NW PERIPHERY OF THESE TWO LOWS DURING THE NEXT 24 HOURS AS THEY SHIFT EVER SO SLIGHTLY SW. SCATTERED SHALLOW CONVECTION SHOULD PERSIST NEAR THE WRN MOST LOW...WHILE SCATTERED SHOWERS AND ISOLATED TSTMS SHOULD CONTINUE NEAR AND ACROSS THE ERN SEMICIRCLE OF THE ERN MOST LOW...AS A S/W MOVING SLOWLY SE ACROSS THE ERN GULF PROVIDES UPPER SHEAR AND SPEED DIVERGENCE. MARINE CONDITIONS ACROSS THE GULF ARE RELATIVELY TRANQUIL...ESPECIALLY ACROSS THE S HALF...WITH SEAS THERE 3 FT OR LESS. 4 FT SEAS WITH AREAS 5-6 FT ARE EXPECTED N OF 26N AND W OF 85W WHERE THIS STRONGER E TO NE WILL FLOW WILL PREVAIL...WITH HIGHER WIND AND SEAS POSSIBLE NEAR TSTMS. A DEEP LAYER TROUGH WILL SWEEP SE ACROSS THE NE AND ERN U.S. OVER THE NEXT 48 HRS...WITH AN ASSOCIATED COLD FRONT EXPECTED TO REACH THE NORTHERN GULF LATE TONIGHT AND EARLY FRI. STRONG HIGH PRESSURE WILL MOVE IN BEHIND THIS FRONT AND N TO NE WINDS SHOULD PICK UP FRI THROUGH THE WEEKEND OVER THE GULF....BUILDING SEAS 5 TO 6 FT IN NE WIND SWELL. BY MON...THE NEXT DEEP LAYER TROUGH SHOULD MOVE INTO THE PLAINS...ENHANCING SOUTHERLY RETURN FLOW IN THE WESTERN GULF. CARIBBEAN... BASED ON RECENT SCATTEROMETER PASSES... WINDS HAVE CALMED CONSIDERABLY ACROSS THE CARIBBEAN FROM RECENT DAYS WITH THE HIGHEST WINDS...TO 25 KT...CONTAINED ACROSS SW SECTIONS AND OFF THE COLOMBIAN COAST. THIS WEAKENED FLOW WILL CONTINUE AS HIGH PRES WELL NE OF THE CARIBBEAN WEAKENS AND SHIFTS FURTHER EAST AHEAD OF THE DEEP LAYER TROUGH MENTIONED ABOVE. HIGH PRES CURRENTLY OFF THE MID ATLC COAST WILL CONTINUE MOVING EASTWARD AND PASS N OF BERMUDA SHORTLY...AND ACT TO MAINTAIN MODERATE TRADE WINDS OVER THE EASTERN CARIBBEAN THROUGH THE WEEKEND. THE DEEP LAYERED TROUGH WILL PUSH THROUGH THE EASTERN DURING THE NEXT 24 HRS AND THEN INTO THE WRN ATLC...FOLLOWED BY STRONG SURFACE HIGH PRES BUILDING INTO THE GULF OF MEXICO/MID ATLC REGIONS. THIS WILL INCREASE THE PRESSURE GRADIENT OVER THE CARIBBEAN AND INCREASE WINDS ONCE AGAIN OVER 20 KT OVER MUCH OF THE WESTERN CARIBBEAN OVER THE WEEKEND...AND SPREAD INTO THE EASTERN CARIBBEAN ON MON. ATLANTIC S OF 31N W OF 55W... A COLD FRONT EXTENDS FROM A DEEP 989 MB SURFACE LOW NE OF THE AREA TO 31N48W TO 24N65W AND THEN INTO THE NW BAHAMAS AND HAS BEEN MEANDERING ACROSS EXTREME SRN FLORIDA AND THE KEYS OVERNIGHT. THE DEEP LAYERED SURFACE LOW WILL MOVES FURTHER E-NE TODAY...AS HIGH PRES BUILDS BEHIND IT OFF THE EASTERN SEABOARD. FRESH TO STRONG N-NE WINDS HAVE ALREADY DIMINISHED OVER THE WATERS BETWEEN N FLORIDA AND BERMUDA...BUT THE NELY WIND SWELL WILL CONTINUE TO AFFECT THE WATERS N THROUGH NE OF THE BAHAMAS AND PUSH THROUGH THE DEEPER GAPS TODAY. LARGE NNW SWELL OF 15 TO 20 FT IS EXPECTED TO PROPAGATE S AND SE...WITH PEAK ENERGY EXPECTED TO JUST MISS THE ERN CARIBBEAN ISLANDS TO THE EAST THROUGH SAT. HOWEVER...TWO PULSES OF LONG PERIOD SWELL...PEAKING AT 2.0-2.5 METERS...IS FORECAST BY WWIII TO AFFECT THE ATLC WATERS OF THE NE CARIB FRI THROUGH SUN...AND MOVE THROUGH THE GAPS AND PASSAGES. AS THIS MAJOR LONG WAVE TROUGH PUSH OFF THE EASTERN U.S. TONIGHT WITH A STRONG SW JET ALOFT AHEAD OF THE TROUGH...DIVERGENT FLOW ALOFT ON THE RIGHT REAR FLANK OF THE JET WILL SUPPORT THE DEVELOPMENT OF A WEAK SURFACE TROUGH JUST EAST OF THE BAHAMAS. AS THE UPPER TROUGH AMPLIFIES NORTH OF THE AREA...THE NEXT COLD FRONT WILL MOVE OFF THE N FLORIDA COAST TONIGHT. MODEL GUIDANCE SUGGESTS THE TROUGH MORPHING INTO A WEAK SURFACE LOW ALONG THE FRONTAL BOUNDARY AND LIFTING OUT TOWARD BERMUDA...BUT MODELS DIFFER ON THE TIMING...WITH THE CONSENSUS MOVING THE LOW NORTHWARD TO BERMUDA LATE FRI NIGHT. THE TRAILING TROUGH WILL EXTEND FROM THE LOW PRES NEAR BERMUDA TO THE SOUTHERN BAHAMAS BY FRI NIGHT...AND FROM 31N60W TO NEAR THE MONA PASSAGE BY SUN. THE DEVELOPMENT OF THE LOW ALONG THE FRONT WILL TIGHTEN THE PRESSURE GRADIENT BETWEEN THE LOW AND HIGH PRES BUILDING BEHIND THE FRONT OVER THE EASTERN U.S. THIS IN TURN WILL RESULT IN A BROAD AREA OF STRONG NE WINDS...PERHAPS AS HIGH AS 30 KT...BEHIND THE FRONT BY LATE SAT. ATLANTIC... NONE. CARIBBEAN... NONE. GULF OF MEXICO... NONE. FORECASTER STRIPLING. TROPICAL PREDICTION CENTER.