000 AGXX40 KNHC 290721 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 230 AM EST THU JAN 29 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO... CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. TWO MAJOR FORECAST CHALLENGES EXIST...(1) THE REINFORCEMENT OF THE SURFACE COLD FRONT EXTENDING FROM THE SE CONUS INTO THE BAY OF CAMPECHE...(2) A MUCH...MUCH STRONGER COLD FRONT POISED TO TRAVERSE THE FORECAST AREA EARLY NEXT WEEK. THE UPPER LEVEL PATTERN IS DE-AMPLIFYING SOMEWHAT WITH THE DEVELOPMENT OF A LONGWAVE TROUGH OVER MUCH OF THE EASTERN TWO-THIRDS OF THE CONUS. THE SURFACE COLD FRONT LEFT BEHIND BY THE SHORTWAVE TROUGH NOW OVER THE NE STATES IS DRAPED FROM THE FLORIDA BIG BEND ACROSS INTO THE SW GULF...WITH MOST OF THE ASSOCIATED UPPER SUPPORT NOW WELL NORTH OF THE REGION AND THE UPSTREAM SURFACE HIGH WEAKENING. NE WINDS IN THE WAKE OF THE FRONT CONTINUE TO DECREASE TO SPEEDS OF 15 TO 20 KT...HIGHEST NEAR THE MEXICO COAST...WITH SHIP AND BUOY REPORTS INDICATING SEAS RELAXING TO 4 TO 6 FT. WHILE THE PROGRESSION OF THE SOUTHERN PORTION OF THE FRONT HAS SUBSTANTIALLY DECREASED...THE NORTHERN EXTENT OF THE FRONT IS FORECAST TO CONTINUE TODAY AS A SERIES OF UPPER LEVEL IMPULSES TRANSLATE EASTWARD IN THE BASE OF THE LONGWAVE TROUGH. ELSEWHERE...TRADE WINDS CONTINUE TO DECREASE ACROSS THE CARIBBEAN AS THE AFOREMENTIONED SURFACE HIGH MOVES EASTWARD AND THE FRONT APPROACHES. HOWEVER...BUOY AND SHIP REPORTS INDICATE SEA HEIGHTS OF UP TO 12 FT IN E SWELL OVER THE SW CARIBBEAN LINGERING FROM THE ANTECEDENT TRADE WINDS. OVER THE NEXT DAY...A HIGH-AMPLITUDE UPPER LEVEL RIDGE OVER THE W CONUS WILL CONTINUE MOVING EASTWARD AS AN UPPER LEVEL JET MAXIMUM DIVES SOUTHEASTWARD TO THE E OF THE RIDGE AXIS. IN RESPONSE...THE LONGWAVE TROUGH WILL DIG SOUTHWARD INTO THE NW GULF ON FRIDAY...WHICH WILL BE EJECTED EASTWARD ON FRIDAY. THIS TROUGH WILL PROVIDE THE UPPER SUPPORT FOR REINFORCING THE FRONT...AS A RELATIVELY STRONG SURFACE HIGH BUILDS OVER S TEXAS AND N MEXICO. THE FRONT WILL THEN SURGE SOUTHEASTWARD ACROSS THE REMAINDER OF THE GULF INTO THE NW CARIBBEAN AND SW N ATLC FRI NIGHT AND SAT...FOLLOWED BY STRONG N TO NE GRADIENT WINDS. GALE FORCE WINDS ARE EXPECTED ACROSS WESTERN PORTIONS FOR THE SW GULF OF MEXICO ZONE...WHERE THE PROXIMITY OF THE HIGHER TERRAIN ALONG THE MEXICO COAST WILL ACT TO FUNNEL THESE WINDS. SREF ENSEMBLE GUIDANCE INDICATES GREATEST GALE POTENTIAL TO BE FROM 30/1200 UTC TO 31/0000 UTC. SEAS WILL BUILD TO 8 TO 13 FT ACROSS A LARGE PART OF THE GULF BY EARLY SAT. IN THE WAKE OF THE FRONT...THE SURFACE HIGH WILL TRANSLATE EASTWARD ACROSS THE SE CONUS...WITH WINDS AND SEAS RELAXING BY SAT NIGHT ACROSS MUCH OF THE GULF AND CARIBBEAN. ON THE OTHER HAND...THE FRONT WILL CONTINUE PROGRESSING SOUTHEASTWARD ACROSS THE SW N ATLC INTO THE TROPICAL N ATLC THROUGH SUNDAY...WHILE IT DISSIPATES FURTHER WEST. IN THE WAKE OF THE FRONT...SEAS WILL BUILD UP TO 20 FT ACROSS PORTIONS OF THE SW N ATLC IN NORTHWESTERLY SWELL LATE SAT. THE TRADES ARE FORECAST TO PICK UP AGAIN IN THE W AND CENTRAL CARIBBEAN EARLY NEXT WEEK AS THE SURFACE HIGH ENTERS THE W AND CENTRAL ATLC. MODELS CONTINUE TO COME INTO AGREEMENT WITH REGARD TO A MAJOR STORM SYSTEM TO IMPACT THE FORECAST AREA EARLY NEXT WEEK. UPPER LEVEL PATTERN LATE THIS WEEKEND ONCE AGAIN FEATURES A LONGWAVE UPPER TROUGH OVER THE CONUS LATE THIS WEEKEND FOLLOWED BY BUCKLING OF THE UPPER FLOW EARLY NEXT WEEK AS A HIGHLY AMPLIFIED RIDGE FORMS OVER THE W CONUS. A STRONG UPPER LEVEL JET MAXIMUM DIVES SOUTHEAST OF THIS RIDGE...HELPING THE UPPER TROUGH DIG SOUTHWARD AND BECOME MORE PROGRESSIVE. THIS JET MAXIMUM IS PARTICULARLY STRONG...BRINGING SUBSTANTIAL UPPER LEVEL ATMOSPHERIC LIFT INTO THE GULF REGION. THIS WILL HELP SPIN UP A SURFACE LOW OVER THE N GULF THAT WILL RACE NORTHEASTWARD... DRAGGING A VERY STRONG COLD FRONT INTO THE NW GULF ON MONDAY...ENTERING THE W ATLC AND W CARIBBEAN ON TUESDAY...FOLLOWED BY GALE FORCE WINDS. OPERATIONAL GFS OFFERS A MORE PROGRESSIVE...YET LESS AGGRESSIVE SCENARIO...COMPARED TO THE ECMWF. IN PARTICULAR...THE OPERATIONAL GFS INDICATES A LOW THAT FORMS ABOUT 200 NM E OF THE ECMWF WITH A LOW THAT IS SOMEWHAT WEAKER THAN THAT OF THE ECMWF. THE FORECAST PACKAGE WILL TEND TO FOLLOW THE GFS...AS THE ECMWF SURFACE LOW PLACEMENT AT 02/1200 UTC IS WEST OF ALMOST ALL MEMBERS OF THE GFS ENSEMBLE AT THAT TIME...WITH A PRESSURE OF 2 TO 4 MB LOWER. THE MORE PROGRESSIVE GFS SOLUTION IS ALSO PREFERRED...GIVEN THE ABSENCE OF ANY STRONG UPPER RIDGING OVER THE E CONUS OR W ATLC. THAT SAID...EXPECT POST FRONTAL GALES IN THE WAKE OF THE FRONT...THOUGH THEIR COVERAGE WILL LIKELY NOT SPAN THE ENTIRE GULF. RIGHT NOW...BEST CHANCE OF GALE FORCE WINDS WILL BE ACROSS PORTIONS OF THE N AND W GULF FOR MON AFTERNOON AND EVENING...AND ACROSS THE SW N ATLC ON TUE. ALSO OF CONCERN IS THE STRONG S FLOW OVER THE N GULF AS THE INCIPIENT LOW QUICKLY DEEPENS MONDAY MORNING...WITH THE OPERATIONAL GFS SHOWING A GALE POTENTIAL. FEEL THAT THE GFS IS OVERDOING THE WINDS GIVEN THE LOW LEVEL STABILITY INHIBITING MIXING WITH THE WARM AIR ADVECTION AHEAD OF THE LOW OVER RELATIVELY COOL WATERS. SEAS BUILD UP TO 15 FT IN THE GULF OF MEXICO AND UP TO 10 FT OVER THE SW N ATLC MON NIGHT WITH WIND WAVES DRIVEN BY SOUTHWESTERLY FLOW AHEAD OF THE FRONT. ATLANTIC... NONE. CARIBBEAN... NONE. GULF OF MEXICO... NONE. FORECASTER COHEN. TROPICAL PREDICTION CENTER.