000 AGXX40 KNHC 300728 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 230 AM EST FRI JAN 30 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO... CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. ...PAIR OF FRONTS FORECAST TO BRING GALES TO PORTIONS OF THE REGION... TWO FORECAST CHALLENGES EXIST THROUGH EARLY NEXT WEEK...(1) THE REINFORCEMENT OF THE SURFACE FRONT EXTENDING FROM THE SW N ATLC INTO THE BAY OF CAMPECHE...(2) A SUBSTANTIALLY STRONGER COLD FRONT POISED TO TRAVERSE THE FORECAST AREA EARLY NEXT WEEK. ...CURRENT CONDITIONS... THE LONGWAVE TROUGH OVER MUCH OF THE EASTERN TWO-THIRDS OF THE CONUS IS BEING EJECTED EASTWARD WITH THE APPROACH OF AN UPPER LEVEL JET MAXIMUM THAT IS DEPARTING A HIGH-AMPLITUDE UPPER RIDGE OVER THE W CONUS. IN RESPONSE...THIS UPPER TROUGH IS DIGGING SOUTHWARD INTO THE GULF OF MEXICO...PROVIDING THE UPPER SUPPORT FOR THE REINFORCEMENT OF THE FRONT CURRENTLY DRAPED FROM THE SW N ATLC INTO THE GULF OF MEXICO. SATELLITE TRENDS ALREADY INDICATE THAT THE FRONT HAS STARTED ITS SOUTHEASTWARD SURGE ACROSS THE GULF...WITH THE 30/0100 UTC ASCAT PASS INDICATING THAT N TO NE WINDS HAVE INCREASED TO 20 KT N OF THE FRONT. THIS SURGE IS BEING AIDED BY SURFACE HIGH PRESSURE BUILDING SOUTHEASTWARD INTO TEXAS IN RESPONSE TO INCREASED SUBSIDENCE W OF THE UPPER TROUGH. ELSEWHERE...TRADE WINDS CONTINUE TO DECREASE ACROSS THE CARIBBEAN AS A RIDGE OVER THE CENTRAL ATLC MOVES EASTWARD AND THE AFOREMENTIONED FRONT APPROACHES. HOWEVER...WAVEWATCH GUIDANCE INDICATES SEA HEIGHTS OF UP TO 10 FT IN E SWELL OVER THE SW CARIBBEAN LINGERING FROM THE RECENT STRONGER TRADE WINDS. ...TODAY AND TONIGHT... THE FRONT IS FORECAST TO SURGE SOUTHEASTWARD ACROSS THE THE GULF OF MEXICO AND WESTERN N ATLC TODAY...ENTERING THE NW CARIBBEAN THIS EVENING....FOLLOWED BY STRONG N TO NE GRADIENT WINDS. GALE FORCE WINDS ARE EXPECTED ACROSS WESTERN PORTIONS OF 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 31/1200 UTC. SEAS WILL BUILD TO 8 TO 12 FT ACROSS A LARGE PART OF THE GULF BY LATE TONIGHT. ACROSS THE SW N ATLC... SOUTHWESTERLY FLOW WILL CONTINUE TO INCREASE AHEAD OF THE FRONT...WITH WIND SPEEDS REACHING 30 KT. WINDS WILL THEN SHIFT TO THE NW IN THE WAKE OF THE FRONT...WITH SIMILAR WIND SPEEDS. GALE FORCE SUSTAINED WINDS ARE NOT EXPECTED IN THE SW N ATLC AREA WITH THIS FIRST FRONT...AS TIME-HEIGHT SECTIONS INDICATE THAT THE LOW LEVEL JET ASSOCIATED WITH THE FRONT WILL LIKELY HAVE PASSED BEFORE THE STRONGER LOW-LEVEL MIXING ARRIVES BEHIND THE FRONT. ALSO...IN THE WAKE OF THE FRONT...SEAS WILL BUILD UP TO 12 FT BY LATE TONIGHT ACROSS PORTIONS OF THE SW N ATLC. ...SATURDAY AND SUNDAY... THE FRONT WILL CONTINUE MOVING ACROSS THE W AND CENTRAL ATLC THIS WEEKEND AND WILL WEAKEN FROM S TO N AS THE BULK OF THE UPPER SUPPORT LIFTS N OF THE FORECAST AREA. AS A RESULT...WINDS AND SEAS IN THE WAKE OF THE FRONT WILL RELAX ACROSS THE GULF AND W ATLC. A SURFACE RIDGE WILL TRANSLATE ACROSS THE N GULF INTO THE SW N ATLC THIS WEEKEND. IN RESPONSE...SOUTHERLY RETURN FLOW WILL INCREASE ACROSS THE GULF OF MEXICO...AND TRADE WINDS WILL PICK UP AGAIN ACROSS THE CARIBBEAN. ALSO...NORTHWESTERLY SWELL ASSOCIATED WITH SEA HEIGHTS UP TO 18 FT WILL LIKELY ENTER THE FAR NORTHERN WATERS BEHIND THE FRONT. ...MONDAY AND TUESDAY... OPERATIONAL MODELS CONTINUE TO COME INTO AGREEMENT WITH REGARD TO A MAJOR STORM SYSTEM TO IMPACT THE FORECAST AREA EARLY NEXT WEEK. THE UPPER LEVEL PATTERN LATE THIS WEEKEND ONCE AGAIN FEATURES A LONGWAVE UPPER TROUGH OVER THE CONUS. THIS WILL BE FOLLOWED BY BUCKLING OF THE UPPER FLOW EARLY NEXT WEEK AS A HIGH-AMPLITUDE UPPER 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 FORECAST TO COUPLE WITH THE SUBTROPICAL JET STREAM...BRINGING SUBSTANTIAL UPPER LEVEL DIVERGENCE INTO THE GULF REGION. THIS WILL HELP SPIN UP A SURFACE LOW OVER THE N GULF THAT WILL RACE NORTHEASTWARD WHILE QUICKLY DEEPENING. THE LOW WILL ALSO PULL A STRONG COLD FRONT INTO THE NW GULF ON MONDAY...ENTERING THE W ATLC AND W CARIBBEAN ON TUESDAY... FOLLOWED BY AREAS OF GALE FORCE WINDS. THE SYSTEM INDICATED BY THE ECMWF HAS COME MORE IN LINE WITH THE MORE PROGRESSIVE SYSTEM OFFERED BY THE OPERATIONAL GFS AND MEMBERS OF THE GFS ENSEMBLE GUIDANCE...LIKELY WITH THE ABSENCE OF MID/UPPER-LEVEL RIDGING OVER THE WESTERN N ATLC. THUS...THE FORECAST GENERALLY FOLLOWS THE GFS...WHICH ALSO INDICATES SOMEWHAT OF A WEAKER LOW. THAT SAID...EXPECT POST FRONTAL GALES ACROSS PORTIONS THE GULF ON MONDAY AS COLD AIR INFILTRATES THE GULF. GALES ARE EXPECTED BOTH AHEAD OF AND BEHIND THE FRONT IN THE SW N ATLC ON TUE...AS BOTH THE GFS AND ECMWF TIME-HEIGHT SECTIONS INDICATE GALE FORCE WINDS ASSOCIATED WITH THE LOW-LEVEL JET LIKELY MIXING TO THE SURFACE. ALSO OF CONCERN IS THE STRONG S FLOW OVER THE N GULF AS THE INCIPIENT LOW DEEPENS MONDAY MORNING. THE GFS APPEARS TO BE OVERDOING THE MAGNITUDE OF THESE WINDS GIVEN THE LOW LEVEL STABILITY GENERATED BY WARM AIR ADVECTION AHEAD OF THE LOW OVER RELATIVELY COOL WATERS. SEAS ARE EXPECTED BUILD UP TO 14 FT IN THE GULF OF MEXICO BY MON NIGHT AND UP TO 18 FT OVER THE SW N ATLC BY TUE NIGHT. ATLANTIC... NONE. CARIBBEAN... NONE. GULF OF MEXICO... GALE WARNING GMZ082 TODAY AND TONIGHT. FORECASTER COHEN. TROPICAL PREDICTION CENTER.