000 AGXX40 KNHC 110759 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 359 AM EDT WED MAR 11 2009 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO... CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... A GENERALLY QUIET WEATHER PATTERN IS FORECAST ACROSS THE GULF OF MEXICO THROUGH LATE WEEK...WITH A PERSISTENT SURFACE RIDGE EXTENDING INTO THE E GULF FROM A SURFACE HIGH OVER THE SW N ATLC. THE RETURN FLOW W OF THE HIGH WILL YIELD SE WINDS OF 15 TO 20 KT ACROSS MUCH OF THE GULF...EXCEPT 5 TO 10 KT CLOSEST TO THE HIGH ACROSS THE NE GULF. THE STRONGEST WINDS WILL BE FOUND ACROSS THE NW GULF AND NEAR THE COAST OF THE YUCATAN PENINSULA. ALSO...AN UPPER RIDGE WILL PREVAIL ACROSS THE GULF AND SE CONUS THROUGH LATE WEEK...WITH GENERALLY FAIR WEATHER CONDITIONS EXPECTED. HOWEVER...THIS RIDGE WILL BREAK DOWN BY LATE THIS WEEK AS A SHORTWAVE TROUGH OVER THE W CONUS PUSHES EASTWARD. A SURFACE FRONT WILL CORRESPONDINGLY APPROACH THE N GULF BY WEDNESDAY NIGHT AS A COLD FRONT BEFORE BECOMING STATIONARY AS THE UPPER FLOW BECOMES ZONAL. THEN...A SHORTWAVE TROUGH OVER THE SW CONUS WILL BE EJECTED EASTWARD CAUSING THE FRONT TO PROGRESS SOUTHEASTWARD ACROSS THE W GULF ON SUNDAY BEFORE WEAKENING. HOWEVER...IN THE ABSENCE OF HIGHLY-AMPLIFIED SYNOPTIC FEATURES OVER THE CONUS...NO PARTICULARLY STRONG SOUTHWARD FRONTAL SURGES ARE EXPECTED THROUGH SATURDAY. HOWEVER...ON SUNDAY...THE SHORTWAVE TROUGH WILL SUPPORT A SOUTHEASTWARD PROGRESSION OF THE FRONT...WITH A SOUTHWARD SURGE FOLLOWED BY N WINDS OF 20 TO 25 KT OVER THE FAR W GULF ON SUNDAY. THROUGH SUNDAY...SEAS OF 4 TO 6 FT WILL BE PRESENT ACROSS MUCH OF THE W GULF...WITH SEAS OF 2 TO 4 FT ACROSS THE E GULF. CARIBBEAN... THE SURFACE PRESSURE GRADIENT ACROSS THE CARIBBEAN CONTINUES TO SLOWLY WEAKEN AS THE SURFACE HIGH IN THE SW NORTH ATLC WEAKENS. IN RESPONSE...THE STRONG TRADE WIND FLOW IS FORECAST TO WEAKEN DURING THE NEXT FEW DAYS...WITH THE STRONGEST WINDS FOUND NEAR THE COAST OF COLOMBIA. HOWEVER...NE TO E WINDS OF 20 TO 30 KT WILL PERSIST ACROSS PORTIONS OF THE SW AND E CARIBBEAN THROUGH LATE WEEK BEFORE DIMINISHING EVEN FURTHER THIS WEEKEND WITH THE APPROACH OF THE COLD FRONT OVER THE NW GULF OF MEXICO. CORRESPONDINGLY...WAVEWATCH LOWERS THE MAX SEA HEIGHTS FOUND NEAR THE COAST OF COLOMBIA FROM 12 FT CURRENTLY TO 10 FT BY FRIDAY. LIKEWISE...THE AREA OF GREATER THAN 8 FT SEAS OVER PORTIONS OF THE SW AND E CARIBBEAN HEIGHTS WILL CONTRACT THROUGH LATE WEEK. ATLANTIC... MAIN FORECAST CHALLENGE DURING THE NEXT FEW DAYS WILL BE STRONG WINDS AND LARGE SWELLS ASSOCIATED WITH THE 994 MB SURFACE LOW NORTH OF THE AREA NEAR 33N53W AS OF 11/0600 UTC. AS FAR AS GLOBAL MODEL GUIDANCE IS CONCERNED...GLOBAL MODELS ARE IN EXCELLENT AGREEMENT WITH REGARD TO THE INTENSITY...POSITION... AND TIMING OF THIS LOW...ALONG WITH THE OVERALL GEOMETRY AND STRENGTH OF THE ASSOCIATED WIND FIELD. FOR THE MOST PART...THE GLOBAL MODELS ARE INDICATING HIGH-END GALE FORCE / LOW-END STORM FORCE WINDS IN THE W SEMICIRCLE OF THE LOW...WHERE THE SURFACE PRESSURE GRADIENT IS BEING STEEPENED BY A SURFACE RIDGE OVER THE W ATLC. THE HIGH-RES QUIKSCAT PASS AROUND 10/2300 UTC SHOWED THE STRONGEST WINDS OF 45 TO 55 KT GENERALLY CONFINED TO THE NW QUADRANT OF THE LOW...GENERALLY IN A SWATH FROM 90 NM TO 180 NM AWAY FROM THE LOW. HOWEVER...ISOLATED 50 KT WINDS ARE FOUND AS FAR SOUTH AS 33N...AS THIS SWATH PIVOTS CYCLONICALLY AROUND THE LOW GIVEN ITS SOUTHEASTWARD TRACK. IN FACT...THE CONTINUED SOUTHEASTWARD TRACK OF THE LOW WILL FURTHER ENHANCE CYCLONIC PROPAGATION OF THIS SWATH INTO THE SW QUADRANT. THE OPERATIONAL GFS INITIALIZES WELL IN A QUICK COMPARISON TO THIS QUIKSCAT PASS...AND TAKES BOUNDARY LAYER WINDS NEAR STORM FORCE INTO THE NORTHERN FRINGES OF THE DISCUSSION AREA. FURTHERMORE... AS THE CYCLONE CONTINUES TO MATURE THROUGH ITS WARM OCCLUSION STAGES AND AS THE OCCLUDED FRONT WRAPS CYCLONICALLY AROUND THE LOW...THE WARM SECLUSION PROCESS WILL TAKE PLACE NEAR THE LOW. IN TURN...INCREASING STATIC INSTABILITY WILL LIKELY INCREASE BANDED CONVECTION IN THE VICINITY OF THE LOW AS WITH THE PREVIOUS LOW IN THIS AREA...FURTHER DEEPENING THE LOW AND INCREASING WINDS OVER THE SOUTHWESTERN SEMICIRCLE. TIME HEIGHT ANALYSES AND CROSS SECTION ANALYSES ACROSS THE WESTERN SEMICIRCLE SHOW SOME POTENTIAL FOR 50 KT WINDS NEAR 900 MB TO COINCIDE WITH STEEPER LOW LEVEL LAPSE RATES DRIVEN BY COLD AIR ADVECTION IN THE WESTERN SEMICIRCLE AND MIX TO THE SURFACE. CONFIDENCE IN THIS SCENARIO IS INCREASING GIVEN THE RECENT UPSWING IN BANDED CONVECTION IN GOES-12 SATELLITE IMAGERY NEAR THE LOW CENTER...AND THIS TREND IS EXPECTED TO CONTINUE WITH WARM SECLUSION CONTINUING. THE UPPER PATTERN ALSO SUPPORTS THE STORM FORCE WIND THREAT...WITH A DISTINCT POSITIVE ISENTROPIC POTENTIAL VORTICITY ANOMALY MAKING AN EQUATORWARD INTRUSION IN THE VICINITY OF THE LOW. GIVEN ALL OF THESE FACTORS...A STORM WARNING IS BEING ISSUED FOR LOCATIONS N OF 30N BETWEEN 56W AND 59W IN THE ATLC FROM 06Z-18Z TODAY...WHILE THE GALE WARNING CONTINUES FOR SURROUNDING LOCATIONS. GIVEN THE JUXTAPOSITION OF THE DYNAMIC FETCH REGION AND ENHANCED WINDS IN THE SW SEMICIRCLE OF THE LOW...WAVEWATCH GUIDANCE IS INDICATING LARGE ACROSS LOCATIONS E OF 60W TRACKING SOUTHWARD AS NW TO N SWELL ACROSS THE SW N ATLC AND TROPICAL N ATLC DURING THE NEXT FEW DAYS. SEA HEIGHTS TO 26 FT COULD BE FOUND BY THIS AFTERNOON W OF THE LOW...WITH SEAS OF 8 TO 13 FT AFFECTING MUCH OF THE NORTHERN TROPICAL N ATLC BY TONIGHT. ATLANTIC... GALE AND STORM WARNINGS IN W SEMICIRCLE OF LOW CENTER N OF AREA. CARIBBEAN... NONE. GULF OF MEXICO... NONE. FORECASTER COHEN. TROPICAL PREDICTION CENTER.