000 AGXX40 KNHC 161933 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 334 PM EDT THU APR 16 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. AT PRESENT OVER THE GULF OF MEXICO... A STATIONARY FRONT EXTENDS FROM THE FLORIDA KEYS INTO THE WEST CENTRAL GULF. THIS FRONT IS FORECAST TO REMAIN NEARLY STATIONARY OR LIFT SLOWLY NORTHWARD AS A WARM FRONT DURING THE NEXT FEW DAYS...AS RETURN FLOW AROUND A BROAD SURFACE RIDGE OVER THE E CONUS BRINGS SE WINDS OF 20 TO 25 KT ACROSS THE WESTERN TWO-THIRDS OF THE GULF REGION. THESE WINDS WILL BUILD MAXIMUM SEAS TO 9 FT OVER THE NW GULF WHERE FETCH LENGTH WILL BE MAXIMIZED. THE SURFACE RIDGE OVER THE E CONUS IS ASSOCIATED WITH A HIGHLY AMPLIFIED UPPER RIDGE OVER THE E CONUS...SOMEWHAT RESEMBLING AN OMEGA BLOCK. THE MAIN PROBLEM OF THE FORECAST PERIOD IS HOW THIS RIDGE WILL BREAK DOWN...AS AN UPPER LOW OVER THE FOUR CORNERS REGION IS EJECTED EASTWARD AS AN OPEN WAVE THIS WEEKEND. GLOBAL MODELS EXHIBIT A WIDE ARRAY OF SOLUTIONS FOR THIS SCENARIO...ALL WITH VARYING AMPLITUDES AND INTENSITIES OF THE RESULTING WEEKEND E CONUS TROUGH. LIKEWISE...THE REGIONAL SPREAD OF CORRESPONDING MODEL SURFACE LOWS COVERS AN AREA ALMOST 600 NM WIDE ACROSS THE EAST CENTRAL CONUS...YIELDING LOW CONFIDENCE IN THE TIMING AND STRENGTH OF THE FRONTAL PASSAGE INTO THE GULF. HOWEVER...THE STRENGTH OF THE ANTECEDENT RIDGE WILL LIKELY SLOW THE EJECTION OF THE UPSTREAM TROUGH...WHICH SUGGESTS THAT THE GFS OVER-AGGRESSIVELY BREAKS THE RIDGE DOWN...PROGRESSING THIS SYSTEM EAST-SOUTHEASTWARD TOO FAST. THE GFS ALSO SPINS UP A CLOSED MID-LEVEL LOW OVER THE MID-MISSISSIPPI VALLEY REGION ON MONDAY AS ITS MORE AGGRESSIVE BREAKDOWN OF THE RIDGE ALLOWS ANOTHER UPPER LEVEL JET STREAK TO DIG THE TROUGH SOUTHWARD... WITH A STRONGER NORTHERLY SURGE INTO THE GULF EARLY NEXT WEEK. THIS POTENTIALLY UNREALISTIC SOLUTION MAY AGAIN BE THE RESULT OF THE GFS TOO QUICKLY BREAKING DOWN THE RIDGE. THE GFS APPEARS TO BE THE OUTLIER AMONG GLOBAL MODELS...WITH THE ECMWF OFFERING A BETTER HANDLE ON THE DEEP-LAYER FEATURES...ALLOWING THE MID-LEVEL TROUGH TO BE SLOWLY EJECTED EASTWARD...WHILE CRESTING THE RIDGE AND FORCING THE RIDGE TO SLOWLY BREAK DOWN. THIS SOLUTION INCLUDES A WEAKER FRONT AS COMPARED TO THE GFS ENTERING THE GULF LATE SUN. THE ECMWF IS ALSO A GOOD COMPROMISE BETWEEN THE UKMET AND NOGAPS...YIELDING A MEAN SURFACE LOW CENTER RESEMBLING CONSENSUS AMONG SREF MEMBERS FOR SUN MORNING OVER SW ARKANSAS. THAT SAID...N WINDS TO 25 KT WILL FOLLOW THE FRONT ALONG THE MEXICO COAST LATE SUN AND MON...WHERE LOCAL TOPOGRAPHY WILL FUNNEL COLDER/DENSER AIR SOUTHWARD. THE WEAKER FRONT WILL LIKELY NOT SUPPORT WINDS TO GALE FORCE AS THE GFS POTENTIALLY OVER-FORECASTS. THE FRONT WILL THEN MOVE SE ACROSS REMAINDER OF GULF MON INTO TUESDAY FOLLOWED BY N WINDS TO 20 KT. ALSO...WITH THE GFS LIKELY OVER-FORECASTING SURFACE WIND SPEEDS...WAVEWATCH GUIDANCE IS LIKELY OVER-FORECASTING POST-FRONTAL WAVE HEIGHTS AS WELL...WITH MAXIMUM WAVE HEIGHTS LIKELY TO REMAIN AT OR BELOW 8 FT. AT PRESENT OVER THE ATLC... A COLD FRONT EXTENDS FROM S OF BERMUDA TO THE FLORIDA KEYS. THE FRONT IS FORECAST TO MOVE SE FOR REMAINDER OF WEEK INTO THE WEEKEND AS MULTIPLE LOW PRES CENTERS N OF THE AREA TRANSLATE E...WITH A REINFORCING FRONT ENTERING THE SW N ATLC THROUGH FRIDAY AFTERNOON. E OF THE INITIAL FRONT...RECENT ASCAT DATA INDICATE SW WINDS OF 20 TO 25 KT E OF FRONT WITH W TO NW WINDS 20 KT W OF FRONT. THESE WINDS WILL CONTINUE WITH THIS INITIAL FRONT AS IT MOVES E OF THE AREA THROUGH SUN. SW WINDS E OF FRONT INCREASE FRI THROUGH SUN AS FRONT ENCOUNTERS A STRONGER SURFACE RIDGE OVER THE E ATLC. ON FRI...STRONG NE WINDS FOLLOW THE REINFORCING FRONT...AS WELL AS WAVE HEIGHTS TO 15 FT IN N SWELL. THESE WAVE HEIGHTS WILL IMPACT MUCH OF SW NORTH ATLC SAT AND SUN WITH MAXIMUM SEA HEIGHTS SUBSIDING BY LATE SUN. IN THE WAKE OF THIS REINFORCING FRONT...SURFACE HIGH PRESSURE WILL BUILD OVER THE SW NORTH ATLC. THE NEXT FRONT...DISCUSSED IN THE GULF OF MEXICO SECTION ABOVE...WILL MOVE OFF THE SE GEORGIA COAST LATE TUESDAY. THIS SOLUTION FOLLOWS THE ECMWF...WHICH YIELDS A RELATIVELY SLOWER FRONTAL PASSAGE AS DISCUSSED ABOVE. SW WINDS OF 20 TO 25 WILL DEVELOP AHEAD OF THIS FRONT ACROSS THE W ATLC ON MONDAY. ACROSS THE CARIBBEAN... FRESH TRADES PERSIST ACROSS CARIBBEAN WITH 1010 MB LOW PRES SUPPORTING NE WINDS TO 25 KT ALONG COAST OF COLOMBIA...WHERE MAXIMUM SEA HEIGHTS TO 10 FT WILL BE PRESENT THROUGH THROUGH THIS WEEKEND. THESE TRADES CONTINUE DURING NEXT SEVERAL DAYS AS SERIES OF SURFACE RIDGES TRAVERSE SE CONUS AND SW N ATLC. ATLC... .NONE.. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FORECASTER COHEN. TROPICAL PREDICTION CENTER.