000 AXPZ20 KNHC 081010 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC WED APR 08 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0915 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 09N84W TO 04N92W TO 03N108W TO 01N129W TO 00N140W. NO SIGNIFICANT CONVECTION IS NOTED. ...DISCUSSION... GAP WINDS... THE STRONG GAP WIND EVENT CONTINUES IN THE GULF OF TEHUANTEPEC WHERE A STORM WARNING REMAINS IN EFFECT. RECENT OBSERVATIONS FROM THIS AREA INCLUDE...SHIP AT 14.8N 95.1W REPORTING 51 KT WINDS AT 07/2100 UTC...SHIP AT 13.8N 94.5W REPORTING 36 KT WINDS AT 07/0000 UTC...AND HIGH RESOLUTION ASCAT PASS SHOWING WINDS TO GALE FORCE EXTENDING AS FAR SW AS 14N 96W. THE AVERAGE WIND VELOCITY FROM THE SURFACE TO 975 MB FROM THE OPERATIONAL NAM CONTINUES TO HAVE THE BEST HANDLE ON THE INTENSITY OF THE WINDS...AS WELL AS THE GEOMETRY OF THE WIND FIELD FOR THIS EVENT...BASED ON OBSERVATIONS. WHILE SATELLITE IMAGERY CONTINUES TO INDICATE COOLING SEA SURFACE TEMPERATURES DUE TO UPWELLING...REINFORCING COLD AIR ADVECTION AND RESULTING STEEP LOW LEVEL LAPSE RATES WILL CONTINUE TO MAINTAIN AN ENVIRONMENT FAVORABLE FOR MIXING THE LOW LEVEL JET TO THE SURFACE. ALSO...ENHANCED NOCTURNAL DRAINAGE FLOW IN THE PRESENCE OF DEEP LAYER DRY AIR EMBEDDED WITHIN A BROAD UPPER LEVEL RIDGE OVER THE SE PORTION OF THE DISCUSSION AREA WILL MAINTAIN THE LIKELIHOOD OF STORM FORCE WINDS UNTIL 08/1500 UTC. THEREAFTER...THE STRONG SURFACE HIGH OVER THE WESTERN GULF OF MEXICO PARTLY RESPONSIBLE FOR THIS EVENT WILL QUICKLY SHIFT EASTWARD AS PRESSURE FALLS COMMENCE OVER THE SOUTHERN PLAINS OF THE CONUS AND CENTRAL MEXICO. WINDS IN THE GULF OF TEHUANTEPEC ARE FORECAST TO FALL BELOW GALE FORCE BY 08/1800 UTC. MAXIMUM SEA HEIGHTS OF 16 FT ARE LIKELY ONGOING...WITH A LARGE AREA OF NORTHEASTERLY SWELL CONTAINING SEAS OVER 8 FT SPREADING DOWNSTREAM OF THE GULF OF TEHUANTEPEC. THIS AREA WILL INCREASE IN SIZE WHILE SPREADING SOUTHWESTWARD...ALTHOUGH MAXIMUM SEA HEIGHTS IN THIS SWELL FALL DURING THE NEXT COUPLE DAYS. INCREASING TRADE WINDS OVER THE CARIBBEAN REGION ARE FORECAST TO EXTEND INTO THE GULF OF PAPAGAYO AND PANAMA DURING THE NEXT FEW DAYS...WHEN SURFACE WINDS ARE EXPECTED TO OCCASIONALLY REACH 20 KT...AND UP TO 25 KT IN THE GULF OF PAPAGAYO. ALSO...SW TO W WINDS TO 20 KT WILL LIKELY DOWNSLOPE OFF THE BAJA CALIFORNIA MOUNTAINS INTO THE NORTHERN GULF OF CALIFORNIA AS A 110-120 KT MID/UPPER-LEVEL JET MAXIMUM SOUTH OF A CLOSED UPPER LOW NEAR 40N123W PROPAGATES EASTWARD WITH THE UPPER LOW. ELSEWHERE... A SURFACE TROUGH OVER THE NW DISCUSSION AREA EXTENDS FROM 30N126W TO 29N130W. THE ASCAT PASS AROUND 08/0300 UTC INDICATES W WINDS UP TO 20 KT NEAR THE TROUGH. THIS SURFACE TROUGH ARE CURRENTLY BEING SUPPORTED BY THE AFOREMENTIONED CLOSED UPPER LOW CENTERED NEAR 40N123W. ALSO...WAVEWATCH GUIDANCE SUGGESTS THAT NW SWELL CONTAINING SEAS UP TO 11 FT IS MOVING SOUTHEASTWARD ACROSS THE NW DISCUSSION AREA. AS THIS SWELL DEPARTS IT SOURCE REGION...MAXIMUM SEAS WILL SUBSIDE...THOUGH NORTHWESTERLY SWELL OF 8 TO 10 FT WILL OVERTAKE A LARGE PART OF THE DISCUSSION AREA THROUGH LATE THIS WEEK. ALSO...THE DEVELOPMENT OF THE SURFACE TROUGH OVER MEXICO DURING THE NEXT FEW DAYS WILL INCREASE NORTHWESTERLY WINDS NEAR THE COAST OF THE BAJA CALIFORNIA...WHERE WINDS WILL LOCALLY REACH 20 KT. FARTHER TO THE S...TRADES ARE BEING ENHANCED ON THE SOUTHERN PERIPHERY OF A BROAD SURFACE RIDGE OVER THE NW QUARTER OF THE DISCUSSION AREA...WHERE NE WINDS TO 20 KT ARE PRESENT. SATELLITE IMAGERY AND SCATTEROMETER DATA INDICATE TWO INVERTED TROUGHS LOCALLY ENHANCING THESE WINDS...THE WESTERN TROUGH EXTENDING FROM 07N139W TO 02N139W...AND THE EASTERN TROUGH EXTENDING FROM 11N114W TO 03N112W. THE AXIS OF THE SUBTROPICAL JET STREAM STRETCHES ALONG A LINE FROM 20N140W TO 24N124W TO SOUTHERN BAJA CALIFORNIA. THIS JET IS ADVECTING ABUNDANT MID TO UPPER LEVEL MOISTURE EASTWARD ACROSS THE DISCUSSION AREA. SE OF THIS JET...ATMOSPHERIC STABILITY AND DEEP LAYERED DRY AIR IN THE VICINITY OF AN UPPER RIDGE OVER THE SE PORTION OF THE DISCUSSION AREA IS SUPPORTING FAIR WEATHER CONDITIONS THERE. LOOKING FURTHER AHEAD...A SHORTWAVE TROUGH CURRENTLY OVER THE GULF OF ALASKA WILL DIVE SOUTHWARD WHILE DEEPENING...AS A VIGOROUS MID/UPPER-LEVEL JET FORCES IT TO DIG SOUTHWARD. COMPUTER MODEL GUIDANCE IS IN GOOD AGREEMENT THAT AN ASSOCIATED SURFACE COLD FRONT WILL APPROACH THE NORTHEASTERN WATERS BY FRIDAY...WITH STRONG WINDS ON EITHER SIDE OF THE FRONT. GUIDANCE ALSO INDICATES THAT A SURFACE LOW WILL DEVELOP NEAR THE CALIFORNIA COAST BEFORE REDEVELOPING INLAND LATE FRIDAY. THIS WILL SERVE TO STRENGTHEN THE SURFACE PRESSURE GRADIENT NEAR THE FRONT...WITH THE THREAT FOR GALE FORCE WINDS NW OF THE COLD FRONT WHERE LOW LEVEL INSTABILITY WILL BE INCREASED. WAVEWATCH GUIDANCE INDICATES SEAS BUILDING TO 15 FT BY LATE FRIDAY IN THE WAKE OF THE FRONT. $$ COHEN