000 AGXX40 KNHC 210141 AAA MIMATS MARINE WEATHER DISCUSSION...UPDATED NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 840 PM EST MON DEC 20 2010 UPDATED WARNINGS SECTION FOR SW N ATLC ZONE 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... HIGH PRES ACROSS THE SE U.S. RIDGING INTO THE GULF TODAY WILL ALLOW FOR INCREASING SOUTHERLY WINDS OVER THE WESTERN GULF TO AROUND 20 KT OVER THE NEXT 24 HOURS...WHILE WINDS AND SEAS SLOWLY SUBSIDE ELSEWHERE. THE HIGH WILL SINK SW INTO THE GULF WED AND DECREASE THE PRES GRADIENT BASIN WIDE. A WEAK COLD FRONT WILL MOVE SW IN A BACK DOOR MANNER ACROSS THE NE GULF WED NIGHT AND REACH FROM NEAR S CENTRAL LOUISIANA TO SW FLORIDA THU BEFORE NEXT FRONT BEGINS TO APPROACH THE TEXAS COASTS AND RETURN FLOW SETS UP AGAIN. THIS NEXT STRONGER FRONT WILL MOVE OFF THE TEXAS COAST FRI WITH WINDS INCREASING TO 20-25 KT BEHIND IT. THE FRONT IS CURRENTLY FORECAST TO EXTEND FROM THE FLORIDA BIG BEND REGION TO TAMPICO BY SAT MORNING. SW N ATLC S OF 31N W OF 55W... COLD FRONT EXTENDED FROM NEAR 31N61W THIS MORNING TO N CENTRAL COAST OF HISPANIOLA THEN SW THROUGH WINDWARD PASSAGE...AND HAS CONTINUED SHIFTING E AND SE AND INCHING CLOSER TO THE PRE FRONTAL TROUGH. GALES WERE VERIFIED ON BOTH SIDES OF THE FRONT BY MORNING SCATTEROMETER PASSES...WITH THESE LOW BIASED RETRIEVALS SHOWING SLY 30-34 KT AS FAR S AS 23N E OF THE TROUGH AND MORE BELIEVABLE N OF 26N. TO THE NW OF THE FRONT...A SECONDARY SURGE OR BOUNDARY BEHIND THE MAIN FRONT WAS USHERING IN NW TO W WINDS 30-40 KT...WITH A PARTIAL ASCAT PASS AND SLIGHTLY BETTER WINDSAT PASS SHOWING THESE WINDS N OF 28W AND LIKELY W OF 66W...WHICH LINES UP NICELY WITH THE S/W MOVING THROUGH BASE OF MEAN DEEP LAYERED TROUGH ACROSS THE W ATLC AND ASSOCIATED CLOUD FIELD. MODELS HAD SUGGESTED THIS IN RECENT RUNS AT VARIOUS BL LEVELS...AND HAVE SINCE ISSUED A GALE WARNING FOR THIS AREA BEGINNING AT 1200 AS OPPOSED TO 1800 UTC TODAY...WHEN WE PREVIOUSLY THOUGHT THIS WOULD BEGIN. AS THE FRONT CONTINUES TO SHIFT E OVER THE NEXT FEW DAYS...AND THE LOW BOMBS OVER THE NW ATLC...THESE GALES WILL PERSIST AND SHIFT E BEHIND THE MAIN FRONT...GENERALLY REMAINED N OF 28N BUT 30-40 KT. HURRICANE FORCE WINDS AND FORECAST WITH THE PARENT LOW AND WILL GENERATE SEAS IN EXCESS OF 30 FT JUST TO THE N OF OUR AREA. THE HIGH BEHIND THE FRONT WILL SINK S INTO THE ERN GULF OF MEXICO WED AND ALLOW ANOTHER REINFORCING FRONTAL BOUNDARY TO DRAG NEARLY W TO E ALONG N PORTIONS WED NIGHT AND INTO N PORTIONS THU...ACTING TO REINFORCE THE PREVAILING NWLY FLOW. NW GALES WILL BE POSSIBLE ACROSS NE PORTIONS BEHIND THIS NEXT BOUNDARY. LARGE NW SWELL GENERATED WITH THIS SYSTEM WILL DOMINATE THE SW N ATLC WATERS NEXT SEVERAL DAYS...PARTICULARLY E OF 70W...WITH WWIII FORECASTING SEAS TO 12 FT PRIMARILY IN NW SWELL TO REACH THE FAR NRN LEEWARDS BY 1800 UTC WED. CARIBBEAN AND TROPICAL N ATLC W OF 55W... DIFFUSE FRONT HAS MOVED S ACROSS THE NW CARIB...ALIGNED W TO E...TO NEAR 17N THEN ARCHES ENE JUST S OF JAMAICA AND ACROSS HISPANIOLA. MODERATE NLY FLOW IS FOUND N OF THIS BOUNDARY WITH N TO NE WINDS GENERALLY 10-15 KT...AND 15-20 KT THROUGH THE WINDWARD PASSAGE AND TO THE LEE OF ERN CUBA. THE TROUGH OUT AHEAD OF THE FRONT HAS SHIFTED INTO THE MONA PASSAGE WITH CONSIDERABLE WEATHER OCCURRING ALONG AND TO THE E OF THE BOUNDARY THIS MORNING. HOWEVER THIS HAS BECOME NEARLY STATIONARY DURING THE DAY AND WEATHER IS OCCURRING ON BOTH SIDES AS CONVERGENCE HAS INCREASED TO THE NW. WEAK SELY FLOW IS OCCURRING TO THE E OF THIS FEATURE. SEAS HAS DIMINISHED GREATLY ACROSS THE REGIONAL ATLC AND ERN CARIB PAST 36 HOURS...WITH PUERTO RICO N BUOY NOW DOWN TO 2 FT. THE FRONT WILL MOVE SE THROUGH PR AND REACH THE USVI TUE MORNING WITH THE PRE FRONTAL TROUGH REACHING THE SRN LEEWARDS. THE FRONT WILL TRAIL OFF SW ACROSS THE CARIBBEAN AS A SHEAR LINE TO ABOUT 15N78W...WITH NELY WINDS ACCELERATING THROUGH THE MONA AND WINDWARD PASSAGES 20-25 KT. THE FRONT IS THEN EXPECTED TO REACH ST MARTEEN TO ST CROIX BY WED MORNING EXTENDING W-SW TO 15.5N75W AS A SHEAR LINE. HIGH PRES WILL HAVE MOVED INTO THE GULF OF MEXICO BY THEN AND WILL ENHANCE BOTH THE NE TRADES ALONG AND S OF THE SHEAR LINE...AND THUS INCREASE LLVL CONVERGENCE AND WEATHER ALONG THE SHEAR LINE AND ACROSS THE SRN CARIB. LONG PERIOD NWLY SWELL WILL HAVE REACHED THE GREATER ANTILLES AND BEGIN TO MOVE THROUGH THE ATLC PASSAGES EARLY WED FOR A SIGNIFICANT BUILDING TREND IN SEAS OVER THE NEXT SEVERAL DAYS. SLY FLOW IS OPENING UP ACROSS THE CENTRAL ATLC AHEAD OF THE PRE FRONTAL TROUGH...WITH SEAS 5 TO 7 FT THIS MORNING IN FADING NE SWELL. WWIII STILL 1-2 FT HIGH IN THIS REGION. TO THE S...A LLVL VORT THAT WE HAVE BEEN FOLLOWING THE PAST FEW DAYS HAS MOVED W INTO A LESS SHEARED ENVIRONMENT...WITH A CONVECTIVE FLARE NEAR THE CENTER EARLIER THAT HAS SINCE BECOME SHEARED. GLOBAL MODELS SHEAR THIS FEATURE AND MOVE IT W ACROSS 60W BY 1200 UTC TUE WITH A BROAD ELY 20 KT WIND FIELD ACROSS THE NRN SEMICIRCLE. HOWEVER MORNING SCATTEROMETER PASSES REVEALED 20-25 KT AND VERY SHARP TROUGH AXIS. HURRICANE MODEL GUIDANCE DOES NOT INTENSIFICATION OF THIS LOW AND SHOWS SOME RECURVATURE TO THE NW THEN N DEPENDING ON HOW DEEP OF A SYSTEM EACH MODEL DEPICTS. STEADY STATE CONDITIONS WOULD BRING A SHARP TROUGH OR LOW INTO BARBADOS EARLY TUE WITH 20-25 KT OF WIND AND NUMEROUS SHOWERS AND SQUALLS WITH POTENTIAL FOR GUSTS TO 30 KT. THESE CONDITIONS THEN SHIFT W TO NW INTO ALL BUT THE SRN WINDWARDS LATER IN THE MORNING. ANY BRIEF INTENSIFICATION WOULD LIKELY INDUCE A DEEPER CIRCULATION AND RECURVE SOMEWHAT AHEAD OF THE APPROACHING FRONT...AND LIFT THESE CONDITIONS FARTHER NW INTO THE NRN WINDWARDS AND POSSIBLY PUT BARBADOS ON THE WEAKER SW PORTION OF THE CIRCULATION. SWELLS GENERATED BEHIND THE FRONT WILL MOVE INTO THE TROPICAL N ATLC WATERS WED AND DOMINATE THROUGH THE WEEKEND. WARNINGS...UPDATED ATLC... .AMZ080...GALE WARNING N OF 28N E OF 74W... CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER STRIPLING/AGUIRRE