000 AXPZ20 KNHC 160952 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC FRI APR 16 2010 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 0945 UTC. ...ITCZ... THE ITCZ AXIS EXTENDS FROM 03N77W TO 08N95W TO 07N135W TO 04N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 30 NM EITHER SIDE OF A LINE FROM 05N89W TO 06N95W...AND ALSO WITHIN 120 NM EITHER SIDE OF A LINE FROM 03N118W TO 06N131W...AND WITHIN 15 NM EITHER SIDE OF LINE 07N118W TO 08N122W...AND WITHIN 30 NM OF 06N139W. ...DISCUSSION... A COMPLEX UPPER LEVEL CYCLONE DOMINATES THE THE NE PACIFIC DRIVING A SERIES OF SHORT WAVE TROUGHS SOUTHEASTWARD OVER THE NW PORTION OF THE DISCUSSION AREA. CURRENTLY...A BAND OF DRY UPPER AIR IS INDICATED NW OF LINE 26N140W TO 32N123W. AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 11N127W WITH AN UPPER RIDGE EXTENDING W TO BEYOND 09N140W...AND AN UPPER RIDGE ALSO EXTENDING NE THROUGH 27N122W TO WELL BEYOND 34N113W. ITCZ CONVECTION IS ENHANCED UNDER THE RIDGE FROM 115W TO 145W...BUT THE RESULTANT DEBRIS MOISTURE REMAINS OVER WITHIN THE AREA FROM 10N TO THE EQUATOR. DEBRIS MOISTURE FROM FORMER ITCZ CONVECTION WELL W OF THE AREA CONCENTRATES INTO A TROPICAL PLUME ADVECTED NE INTO THE AREA ALONG THE PERIPHERY OF THE UPPER RIDGE... ROUGHLY WITHIN 300 NM EITHER SIDE OF LINE 20N140W TO 27N113W WITH SOME OF THE MOISTURE CONTINUING N UNDER THE RIDGE CREST OVER THE SW CONUS. AN UPPER CYCLONE IS OVER W TEXAS NEAR 31N104W WITH AN UPPER TROUGH EXTENDING SSE ACROSS OLD MEXICO ALONG 26N103W TO A BASE OVER THE TROPICAL PACIFIC AT 07N94W. AN UPPER RIDGE EXTENDS W FROM S AMERICA OVER THE DEEP TROPICS E OF 88W TO A SHARP CREST AT 07N88W. VERY DRY UPPER AIR IS ADVECTED SE BEHIND THE UPPER TROUGH OVER THE AREA FROM 25N TO 05N BETWEEN 110W AND 95W. ITCZ CONVECTION IS ENHANCED JUST E OF THE UPPER TROUGH AND UNDER THE W END OF THE TROPICAL RIDGE...ROUGHLY ALONG 06N BETWEEN 87W AND 95W...WITH THE DEBRIS MOISTURE ADVECTED NE ACROSS COSTA RICA AND PANAMA AND OVER THE SW CARIBBEAN SEA. AT THE SURFACE...HIGH PRES 1018 MB IS CENTERED AT 25N124W AND IS BEGINNING TO SLOW THE EASTERN PROGRESSION OF A COLD FRONT NOW EXTENDING ALONG 32N129W TO 23N140W. THE TIGHT GRADIENT BETWEEN THE RIDGE AND FRONT HAS RELAXED SOME THE PAST FEW HOURS AND NOW SUPPORTING SOUTHERLY SURFACE WINDS AT 20 TO 25 KT. THIS FRONT IS EXPECTED TO DISSIPATE OVER THE DISCUSSION AREA TODAY. BUT...THE UPPER CYCLONE N OF THE AREA WILL SEND ANOTHER SURFACE COLD FRONT INTO THE AREA TONIGHT ACCOMPANIED BY AT LEAST 20 TO 25 KT SURFACE WINDS ON EITHER SIDE OF THE FRONT. EXPECT THE SURFACE HIGH TO AGAIN BLOCK...OR AT LEAST SLOW THIS SECOND FRONT AS WELL...WITH FRONTAL WAVE LOW FORMATION ALONG THE FRONT NEAR 28N130W LATE SAT. FURTHER S...NE TRADES OF 20 KT ARE OBSERVED FROM 08N TO 13N BETWEEN 113W AND 135W WITH THIS AREA OF STRONGEST TRADES EXPECTED TO SHIFT SLIGHTLY NW ON SAT BEFORE THE TRADES RELAX TO LESS THAN 20 KT SUN. THE PRESSURE GRADIENT BETWEEN THE AFOREMENTIONED SURFACE HIGH PRESSURE...AND A TROUGH OVER THE SIERRA MADRE OCCIDENTAL...IS PRODUCING NW SURGES TO 20 KT WITHIN 180 NM W OF THE NORTHERN BAJA PENINSULA...EXPECTED TO PERSIST THROUGH SAT. LONG PERIOD NW SWELL AND CROSS EQUATORIAL LONG PERIOD SW SWELL HAS BEEN PROPAGATING N ACROSS THE DISCUSSION AREA FOR SEVERAL DAYS RESULTING IN CONFUSED SEAS WHERE THE DIFFERENT WAVE GROUPS INTERSECT. TO FURTHER COMPLICATE THE SEA STATE...NE TRADE GENERATED SWELLS ARE ALSO OBSERVED FROM THE ITCZ TO 20N W OF 100W. $$ NELSON