000 AXPZ20 KNHC 300227 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC TUE APR 30 2013 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0130 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 09N73W TO 05N79W TO 09N85W TO 08N110W...WHERE IT TRANSITIONS TO THE INTERTROPICAL CONVERGENCE ZONE...CONTINUING ON TO LOW PRES NEAR 09N130W 1007 MB...TO BEYOND 05N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 120 NM S OF MONSOON TROUGH BETWEEN 86W AND 97W. SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM EITHER SIDE OF ITCZ BETWEEN 103W AND 122W. SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION NOTED FROM 06N TO 12N BETWEEN 123W AND 133W...AND FROM 01.5N TO 05N BETWEEN 122W AND 125W. ...DISCUSSION... AN UPPER LEVEL BLOCKING PATTERN PERSISTS ACROSS THE NE PACIFIC THIS EVENING. WATER VAPOR IMAGERY INDICATES A BROAD MIDDLE TO UPPER LEVEL CYCLONE CENTERED NEAR 290N139W...AND IS DRIFTING W AROUND THE SOUTHERN PERIPHERY OF AN UPPER LEVEL ANTICYCLONE TO ITS N ALONG 40N. DRY AIR AND MODERATE TO STRONG SUBSIDENCE PREVAIL N OF 20N. A SURFACE RIDGE IS ANCHORED BY A 1031 MB HIGH CENTERED NORTH OF THE DISCUSSION AREA NEAR 42N139W. THE COMBINATION OF THE BROAD AREA OF DRY STABLE AIR AND HIGH PRES CENTERED WELL N OF THE AREA CONTINUES TO KEEP CONDITIONS RELATIVELY QUIET FOR THE NEAR TERM OVER A MAJORITY OF THE BASIN N OF 15N W OF 110W. A WEAK IMPULSE OF MID-LEVEL ENERGY IS EXPECTED TO SLIDE SOUTH ALONG THE CALIFORNIA COAST TONIGHT AND TUE WITH STRONG NORTHERLY WINDS SPREADING INTO NE PORTIONS OF THE DISCUSSION AREA...RESULTING IN SEAS BUILDING TO 10 FT BY EARLY WEDNESDAY IN THE VICINITY OF 30N126W. SEAS ABOVE 8 FT WILL GENERALLY SPREAD S TO 26N BETWEEN 118W AND 137W IN NORTH SWELL BY 48 HOURS. THE REMAINDER OF THE WEATHER ACROSS THE AREA S OF 20N W OF 110W REMAINS FOCUSED ON A 1007 MB SURFACE LOW EMBEDDED WITHIN THE ITCZ AXIS ANALYZED ALONG 09N130W...WHERE AN AFTERNOON PARTIAL ASCAT PASS SUGGESTED A LOW CENTER DEVELOPING. THE BROAD MIDDLE TO UPPER LEVEL CYCLONE MENTIONED ABOVE EXTENDS A TROUGH SE INTO THE TROPICS NEAR 14N140W...WHERE A SHORTWAVE TROUGH IS MOVING THROUGH THE BASE. A SHORTWAVE RIDGE HAS DEVELOPED NE OR AHEAD OF THIS SHORTWAVE TROUGH...PROVIDING DIVERGENCE ALOFT FOR DEEP CONVECTION MENTIONED ABOVE OCCURRING ALONG AND E OF THE LOW CENTER AT 130W. BURSTS OF DEEP CONVECTION IN THIS VICINITY DURING THE PAST 12 TO 18 HOURS HAVE AIDED IN THE WWD SHIFT OF THE UPPER RIDGE ACROSS THIS AREA FROM RECENT DAYS...NOW CENTERED ALONG 117W AND S OF 23N. THE PRESSURE GRADIENT BETWEEN THE HIGH WELL N OF THE AREA AND THE DEVELOPING LOW ALONG THE SURFACE TROUGH IS PRODUCING AN AREA OF 20-25 KT NE TO E WINDS ACROSS THE N SEMICIRCLE OF THE LOW TO 13N. CONVECTION ACROSS THE AREA WILL PERSIST OVERNIGHT UNDER FAVORABLE MIDDLE TO UPPER LEVEL CONDITIONS...THEN GRADUALLY WEAKEN W OF THE LOW LATE TUESDAY... AS THE LOW GRADUALLY COLLAPSES. E OF 110W...RELATIVELY TRANQUIL CONDITIONS ARE NOTED IN OBSERVATIONAL DATA...RECENT SCATTEROMETER PASSES...AND LATEST GLOBAL MODEL DATA. OF NOTE...STRONG SW SWELL FROM A SOUTHERN HEMISPHERE LOW PRESSURE SYSTEM CONTINUES SPREADING NORTHEASTWARD REACHING THE MEXICAN AND CENTRAL AMERICAN COAST WITH WAVE PERIODS IN THE RANGE OF 15 TO 18 SECONDS. THIS LONG PERIOD SWELL EVENT IS EXPECTED TO PERSIST THROUGH LATE THURSDAY. $$ STRIPLING