000 AXPZ20 KNHC 201619 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC THU MAY 20 2010 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...TROPICAL WAVES... TROPICAL WAVE ALONG 84W N OF 02N IS MOVING W AT 10 KT. LONG TERM ANIMATIONS OF SATELLITE AND VARIOUS MODEL FIELDS SUGGEST THAT THIS WAVE MAY BE A BIT FURTHER W...ALONG 88W. THE DOWNSTREAM ENVIRONMENT IS CHARACTERIZED BY ELONGATED LOW TO MID LEVEL TROUGHING EXTENDING FROM THE ITCZ ALONG 100W...NE INTO EXTREME S MEXICO. THIS PATTERN HAS SIGNIFICANTLY EFFECTED THE TYPICAL DUE WWD MOTION OF WAVES MOVING INTO THE FAR EPAC. CLUSTERS OF MODERATE TO STRONG CONVECTION WERE NOTED N OF 05N BETWEEN 80W AND 87W...AND E OF WAVE. DUE TO THE TROUGHING DOWNSTREAM OF THIS WAVE...VERY SLOW W TO NW MOTION IS EXPECTED DURING THE NEXT 24 HOURS WHILE UPPER LEVEL CONDITIONS REMAIN FAVORABLE FOR CONTINUED MODERATE TO DEEP CONVECTION. TROPICAL WAVE ANALYZED ALONG 105/106W WITH A WEAK LOW TO MID LEVEL CYCLONIC CIRCULATION INDICATED IN SATELLITE IMAGERY NEAR 08.5N105W. CONVECTION NEAR THE WAVE REMAINS MODEST THIS MORNING AS THE HAVE IS ENTERING THE WRN PERIPHERY OF THE UPPER RIDGE ACROSS THE REGION. ADDITIONALLY...MID LEVEL SHEAR IS PULLING ASSOCIATED MOISTURE OFF TO THE NE. TROPICAL WAVE ANALYZED ALONG 126/127W WITH A 1009 MB LOW NEAR 08N126.5W. THIS WAVE IS JUST S OF INCREASING WLY SHEAR ALOFT...WITH AN APPROACHING S/W JUST UPSTREAM. THE MID AND UPPER LEVELS NEAR THIS WAVE APPEAR RELATIVELY DRY IN WATER VAPOR IMAGERY. HOWEVER LOW LEVEL MOISTURE AS DEPICTED IN TPW ANIMATIONS IS ELONGATED IN A RELATIVELY NARROW BAND TYPICAL OF THE ITCZ. ONLY MODEST CONVECTION IS TO BE EXPECTED WITH THIS WAVE NEXT 24 HOURS. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS WAS ANALYZED ALONG 10N78W TO 07N85W TO 08.5N108W TO 07N112W TO 08N126W TO 06N140W. SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120 NM N OF AXIS E OF 80W...AND WITHIN 210 NM N OF AXIS BETWEEN 87W AND 102W. ...DISCUSSION... A WEAKENING COLD FRONT IS GRAZING THE NW WATERS AND IS USHERING IN HIGH PRES BEHIND IT STEMMING FROM A 1029 MB HIGH NEAR 35N143W. THERE IS A TIGHT PRES GRADIENT IN PLACE BETWEEN THE RIDGING OVER MUCH OF THE FORECAST AREA N OF 20N AND TROUGHING FROM THE SOUTHERN PLAINS THROUGH CENTRAL MEXICO. NW TO N WINDS ALONG THE W COAST OF BAJA CALIFORNIA ARE IN THE 20-25 KT RANGE ACCORDING TO AN EVENING WINDSAT PASS...WHILE SHIP DGSE REPORTED 27 KT NEAR 23N111W AT 0600 UTC. THE STRONG PRES GRADIENT OVER NE WATERS WILL BE MAINTAINED THROUGH THE FORECAST PERIOD AS THE ENERGY ASSOCIATED WITH THE AFOREMENTIONED COLD FRONT MOVES INTO THE SW U.S. AND REINFORCES THE TROUGHING OVER THE CONTINENT WHILE THE SUBTROPICAL HIGH CONTINUES TO BUILD BEHIND THE COLD FRONT. LOOK FOR 20-25 KT WINDS TO EXPAND W TO NEAR 127W OVERNIGHT TONIGHT AND REMAIN IN PLACE THROUGH FRI. ALSO...LOOK FOR NE TRADE WINDS TO EXPAND N BEYOND 25N OVER THE NEXT FEW DAYS AS A RESULT OF THE INCREASED PRES GRADIENT BETWEEN THE BUILDING SUBTROPICAL HIGH AND THE ITCZ TO THE S. AN UPPER LEVEL ANTICYCLONE WAS CENTERED NEAR 14N92W AND GRADUALLY SHIFTING W...WITH A RIDGE AXIS EXTENDING W TO 120W AND A WEAKENING PORTION SE THROUGH NRN NICARAGUA. THE DIFFLUENT CONDITIONS INDUCED BY THE RIDGE ALOFT IS ENHANCING THE AFOREMENTIONED MODERATE TO STRONG CONVECTION TO THE E OF THE TROPICAL WAVE ALONG 83W. THE RIDGE ALSO EXTENDS SW OF THE ANTICYCLONE CENTER TOWARD 12N120W AND THEN TURNS S TOWARD ANOTHER ANTICYCLONE NEAR 08N126W. MEANWHILE...A 50-70 KT W-SW UPPER JET PARALLELS THE RIDGE AXIS WITH ITS JET CORE APPROXIMATELY 510 NM N OF THIS RIDGE. THE JET IS TRANSPORTING CONVECTIVE DEBRIS FROM THE ITCZ NORTHEASTWARD INTO SOUTHERN MEXICO. A 1009 MB LOW PRES CENTER IS EMBEDDED IN THE ITCZ NEAR 08N125W...UNDER THE WESTERN ANTICYCLONE. DESPITE FAVORABLE CONDITIONS ALOFT AND AVAILABLE LOW LEVEL MOISTURE...THERE IS NO SIGNIFICANT CONVECTION CURRENTLY ASSOCIATED WITH THIS LOW. CROSS-EQUATORIAL LONG PERIOD SW SWELL HAS REACHED MUCH OF THE PACIFIC COASTLINE WITHIN THE FORECAST AREA WITH WAVE HEIGHTS IN THE 4-6 FT RANGE...WITH THE EXCEPTION OF THE W COAST OF BAJA CALIFORNIA WHERE NW WIND WAVES HAVE DRIVEN SEAS UP TO 6-8 FT. THE HIGHEST ENERGY WAVE FIELD...WITH SWELL UP TO 20 SECONDS AND SIGNIFICANT WAVE HEIGHTS TO 11 FT...IS CURRENTLY PROPAGATING THROUGH SW WATERS PRIMARILY SW OF A LINE FROM 00N98W TO 20N130W. THIS WAVE TRAIN IS EXCEPTED TO REACH THE MEXICAN AND CENTRAL AMERICAN COAST BY FRI MORNING AND WILL INCREASE WAVES TO 10 FT IN 20 SECOND SWELL IN THE COASTAL WATERS FRI INTO THE WEEKEND...MAKING FOR DANGEROUS SURF CONDITIONS ESPECIALLY ON SOUTH FACING BEACHES. SEAS ARE EXPECTED TO RISE ABOVE 8 FEET OVER THE ENTIRE FORECAST AREA BY SAT MORNING AS THE SW SWELL SPREADS NORTH THROUGH THE REGION. $$ SCHAUER/STRIPLING