000 AGXX40 KNHC 051936 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 100 PM EST THU MAR 5 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO... CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. UPPER PATTERN OVER THE AREA IS DOMINATED BY A REX BLOCK SPANNING ACROSS THE ENTIRE ATLC...BETWEEN 05E AND 80W. A BROAD UPSTREAM RIDGE IS ACROSS THE GULF OF MEXICO...WITH L/W TROUGHS ACROSS THE W ATLC...AND EXTREME WRN EUROPE INTO NW AFRICA...WITH THE UNDER CUTTING LOW NEAR 24N 32W. AN INTERESTING AND UNUSUAL PATTERN IS FORECAST TO EVOLVE OVER THE CENTRAL ATLC IN THE NEXT 36-72 HOURS AS HIGH LAT FEATURES MOVE PROGRESSIVELY EWD...AND THE MID LAT BLOCKING PERSISTS. BY 48 HOURS...TWIN UPPER LEVEL CUT OFF LOWS ARE FORECAST ACROSS THE SUB TROPICAL ATLC...NEAR 28N 57W...AND 26N 23W...WITH THIS WESTERNMOST LOW TO REFLECT A GALE CENTER AT THE SURFACE. .GULF OF MEXICO... HIGH PRES RIDGE ALOFT COVERS THE GULF OF MEXICO...WHILE A 1034 HIGH OFF THE CAROLINAS RIDGES WSW ACROSS THE NE AND NRN GULF. THIS IS YIELDING 15-20 KT FLOW AROUND THE PERIPHERY OF THIS ANTICYCLONIC CIRCULATION...AND 20 KT FLOW WITH SMALL AREAS UP TO 25 KT IN THE FLORIDA STRAITS AND OFF THE YUCATAN INDICATED IN MORNING QUIKSCAT PASSES. SEAS RUNNING 6 TO 7 FT ACROSS THESE AREAS AND UP TO 8 FT OFF NW COAST OF CUBA AND ACROSS THE YUCATAN CHANNEL. THE SURFACE HIGH WILL SHIFT ENE AND ELONGATE THROUGH 48 HOURS AND THEN REORGANIZE OFF OF THE FLORIDA COAST...ALL THE WHILE PRODUCING LITTLE SIGNIFICANT CHANGE IN THE OVERALL PATTERN ACROSS THE GULF. .ATLANTIC... THE COLD FRONT HAS BECOME NEARLY STATIONARY...EXTENDING FROM THE W CENTRAL ATLC SW TO ERN PUERTO RICO...WHERE IT HAS BECOME SOMEWHAT DIFFUSE...EXTENDING AS A BROADER ZONE OF LOW CLOUDS AND SHOWERS SSW INTO THE CENTRAL CARIB...AND THEN WSW TOWARDS THE SW CARIB. THE WEAK BOUNDARY HAS BEEN DRIFTING BACK TOWARDS THE W ALONG THE N COAST OF PUERTO RICO...WITH BROAD INVERTED TROFFING SUGGESTED ACROSS THE NE CARIB BY STLT IMAGERY. AN UPPER LOW IS FORECAST TO PINCH OFF IN THE BASE OF THE L/W TROF EXTENDING S INTO WRN ATLC DURING THE NEXT 36-48 HOURS...INVOF THE PERSISTENT FRONTAL BOUNDARY. GLOBAL MODELS ALL RESPOND BY DEVELOPING A SURFACE LOW AND GALES IN NW SEMI CIRCLE OF LOW. THIS IS A MONTH OR TWO EARLY TO SEE THIS TYPE OF DEVELOPMENT AT THIS LATITUDE. GFS DUMBBELLS THE SURFACE LOW BACK TO THE W AND THEN SW BRIEFLY BEFORE SLOWLY LIFTING OUT TO THE ENE...WHICH SHOWS A BIT MORE SW MOTION THAN ALL OTHER GLOBAL MODELS FROM THE 00Z AND 12Z RUNS. IN DOING SO...GFS SUGGESTS GALES COULD START AS EARLY AS 12-18Z FRI...WHICH IS ALSO SUGGESTED BY THE CANADIAN MODEL. HAVE OPTED ATTM TO MOVE GALE WARNING TO 00Z SAT (FROM 12Z SAT) WHICH IS A BIT FASTER THAN THE OTHER GLOBAL MODELS...BUT NOT AS FAST AS GFS AND CANADIAN. A BROAD ZONE OF N TO NE FLOW WILL DEVELOP ON BACK SIDE OF LOW AND W OF FRONT TO PRODUCE VERY HIGH SEAS THAN WILL MOVE S INTO THE NE CARIB AND THROUGH THE ATLC PASSAGES THERE FOR ROUGH AND SHIFTING SEAS IN A MIX OF N AND NE WAVES AND SWELL. 12 FT SEAS ARE FORECAST TO INVADE THE ATLC WATERS OF PUERTO RICO/USVI AND ERN DOM REP BY 12Z SAT...WITH A SECONDARY NNE PULSE OF MODERATE PERIOD SWELL THEN FORECAST TO AFFECT THE ENTIRE REGION FROM THE BAHAMAS TO THE WINDWARDS AFTER THE LOW BEGINS TO LIFT OUT AND WINDS FILL IN ON THE BACK SIDE SUN-MON. WWIII ENSEMBLE SHOWING MAX SWH ON BACK SIDE OF THIS GALE CENTER AT 32 FT 12Z SUN. A SMALL AREA OF GALES ARE POSSIBLE ON THE E AND NE SIDE OF THIS LOW/GALE CENTER SAT. GFS SUGGESTS THE LOW WILL OCCLUDE SUN-MON AND WILL BE INTERESTING TO SEE HOW MUCH CONVECTION DEVELOPS AROUND THE CENTER OVER 24-25 DEG C SST. SURFACE HIGHS ON EITHER SIDE OF THIS LOW WILL MAINTAIN MODERATE TO FRESH WINDS AND NELY WIND SWELL. .CARIBBEAN... WEAKENING FRONTAL ZONE APPEARS TO HAVE DRIFTED SLIGHTLY W AND SW TODAY...WITH STRONG NNE FLOW ACROSS THE GREATER ANTILLES AND THROUGH THE MAJOR PASSAGES YIELDING 25-30 KT WINDS PER MORNING SCATTEROMETER PASSES. FRESH TO STRONG FLOW WILL PERSIST TO THE W OF THE FRONTAL BOUNDARY THROUGH 12Z SAT BEFORE THE FLOW BECOMES MORE ENE ACROSS MOST OF THE BASIN AND STRONGEST FLOW BECOMES CONFINED TO S AND SW CARIB. AS THE CENTRAL ATLC GALE BEGINS TO DEVELOP...SURFACE HIGH ACROSS THE FAR W ATLC WILL BUILD MODESTLY INTO THE N CARIB AND IS FORECAST TO FORCE FRONTAL REMNANTS MORE SE AND INTO THE LEEWARDS ON FRI...AND WINDWARDS ON SAT. NELY FLOW OFF OF THE COAST OF COLOMBIA MAY GUST TO AND APPROACH SUSTAINED 35 KT WINDS FRI AND A GALE WARNING MAY BECOME NECESSARY THERE. OTHERWISE...HIGHEST WINDS WILL REMAIN DOWNWIND OF PASSAGES...WITH PEAK SEAS IN THE CENTRAL AND SW CARIB AT 10-14 FT TONIGHT BUILDING 12-15 FT FRIDAY NIGHT IN NELY WIND SWELL. WIND AND SEAS ACROSS THE FAR ERN CARIB FORECAST TO REMAIN MODEST. ATLANTIC... NONE. CARIBBEAN... NONE. GULF OF MEXICO... NONE. FORECASTER STRIPLING. TROPICAL PREDICTION CENTER.