000 AGXX40 KNHC 260718 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 218 AM EST MON JAN 26 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO... CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. NEARLY ZONAL FLOW IN THE MID AND UPPER LEVELS IS KEEPING THE MAJORITY OF CONTINENTAL POLAR AIR SURGES NORTH OF THE FORECAST AREA AT PRESENT. BY LATE WEEK...THE UPPER PATTERN IS FORECAST TO BECOME MORE AMPLIFIED...AS A VIGOROUS UPPER LEVEL TROUGH OVER THE EAST PACIFIC IS EJECTED EASTWARD OVER THE CONUS. IN THE MEANTIME...SURFACE RIDGING OVER THE SE CONUS IS INDUCING SOUTHEASTERLY RETURN FLOW ACROSS THE GULF REGION. THIS FLOW IS FORECAST TO INCREASE IN RESPONSE TO THE INCREASING PRESSURE GRADIENT ON THE SW PERIPHERY OF A SURFACE HIGH THAT WILL TRAVERSE THE W AND CENTRAL ATLC THIS WEEK. THESE WINDS COULD EXCEED 20 KT ACROSS THE W GULF AT TIMES...PARTICULARLY ON TUESDAY. THE INCREASING PRESSURE GRADIENT WILL ALSO CAUSE A STRENGTHENING TREND IN EASTERLY TRADES ACROSS THE CARIBBEAN BASIN AND SW N ATLC THROUGH THIS WEEK...WITH THE STRONGEST WINDS OF 30 KT NEAR THE COAST OF COLOMBIA. THESE TRADES WILL MAINTAIN 8 TO 10 FT SEAS ACROSS A LARGE PART OF THE CARIBBEAN AND SW N ATLC... WITH SEAS TO 12 FT NEAR THE COAST OF COLOMBIA. ALSO...EPISODES OF NORTHWESTERLY SWELL OF 8 TO 10 FT WILL PERIODICALLY BRUSH FAR NORTHERN PORTIONS OF THE FORECAST AREA THROUGH THE WEEK ASSOCIATED WITH A SERIES OF COLD FRONTS NORTH OF THE DISCUSSION AREA. FORECAST CHALLENGE ARRIVES TUESDAY NIGHT...AS THE AFOREMENTIONED UPPER LEVEL TROUGH TRANSLATES EASTWARD AND BECOMES SHEARED OUT FROM THE NEW ENGLAND STATES TO THE SOUTHERN PLAINS. A COLD FRONT ASSOCIATED WITH THIS TROUGH WILL PLUNGE SOUTHWARD ACROSS THE SOUTHERN PLAINS...ENTERING THE NW GULF TUESDAY NIGHT. SOME INCONSISTENCY AMONG OPERATIONAL MODELS EXISTS...WITH THE NAM BEING THE MOST MOST PROGRESSIVE COMPARED TO THE ECMWF AND GFS. FEEL THE NAM HAS THE BEST HANDLE ON THE COLD FRONT MOTION... GIVEN THE CLIMATOLOGICALLY FAST SOUTHWARD SURGES OF COLD FRONTS OVER THE W GULF WITH RELATIVELY STRONG SURFACE HIGHS TO THE NW. THAT SAID...EXPECT THE FRONT MOVING OFF THE SE TEXAS COAST AROUND 04Z WED...WITH THE WESTERN PORTION OF THE FRONT SURGING SOUTH OF THE INTERNATIONAL BORDER BY 10Z WED. THEREAFTER...THE FRONT IS FORECAST TO BECOME TEMPORARILY STATIONARY FROM VERACRUZ TO THE FLORIDA BIG BEND. AT THE SAME TIME...INCREASING COLD AIR ADVECTION AND INCREASING HEIGHT FALLS IN THE MID/UPPER-LEVELS WILL INFILTRATE MUCH OF THE CONUS...RESULTING IN THE DEVELOPMENT OF A LONGWAVE TROUGH OVER MUCH OF THE CONUS. IN TURN...THIS WILL STRENGTHEN SUBSIDENCE AND BUILD A SURFACE HIGH UPSTREAM OF THE TROUGH AXIS OVER THE SOUTHERN PLAINS. ONCE THE LONGWAVE TROUGH IS EJECTED EASTWARD BY A DEVELOPING WEST CONUS COAST RIDGE... GFS AND ECMWF MOVE THE SURFACE HIGH SOUTHEASTWARD OVER THE NW GULF...CAUSING THE PRE-EXISTING FRONT TO SURGE SOUTHEASTWARD ON FRIDAY AND SATURDAY. ECMWF IS SLIGHTLY LESS AGGRESSIVE WITH THE SOUTHEASTWARD SURGE. HOWEVER...GIVEN GOOD CONSISTENCY AMONG GFS ENSEMBLES IN THE STRENGTH AND INTENSITY OF THE SURFACE HIGH OVER TEXAS...WENT WITH THE STRONGER SURFACE HIGH AND STRONGER FRONTAL PUSH ACROSS THE GULF. CORRESPONDINGLY...INCREASING N TO NE GRADIENT FLOW IN THE WAKE OF THE FRONT WILL REACH SPEEDS OF 25 TO 30 KT OVER A LARGE AREA OF THE GULF. HOWEVER...MODULATIONS TO THE SURFACE FLOW DUE TO PRESENCE HIGHER TERRAIN OVER MEXICO WILL LIKELY RESULT IN GALE FORCE WINDS ACROSS PORTIONS OF THE W GULF AND BAY OF CAMPECHE FRIDAY AND SATURDAY. THIS SAME FRONT WILL MOVE OFF THE SE CONUS INTO THE W ATLC ON FRIDAY...WITH INCREASING SW FLOW AHEAD OF THE FRONT. GFS INDICATES SOME POTENTIAL FOR GALE FORCE GUSTS WITH STEEPER LAPSE RATES AHEAD OF THE FRONT COINCIDING WITH AN INCREASING LOW-LEVEL JET ASSOCIATED WITH THE FRONT. ECMWF IS SUBSTANTIALLY LESS AGGRESSIVE WITH THIS JET...AND SUGGESTS WINDS UNDER GALE FORCE. HELD OFF ON ANY GALE IN THIS REGION WITH THE EXISTING UNCERTAINTY. WAVE HEIGHTS IN THE WAKE OF THE FRONT WILL INCREASE TO AS HIGH AS 14 FT OVER THE GULF AND AS HIGH AS 9 FT OVER THE W ATLC BY FRIDAY EVENING. ATLANTIC... NONE. CARIBBEAN... NONE. GULF OF MEXICO... NONE. FORECASTER COHEN. TROPICAL PREDICTION CENTER.