000 AXPZ20 KNHC 180329 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC FRI NOV 18 2011 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 0300 UTC. ...SPECIAL FEATURE... A 1008 MB AREA OF LOW PRES IS EMBEDDED IN THE MONSOON TROUGH NEAR 09N95.5W MOVING W AROUND 8 KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 90 NM OF THE LOW CENTER. SW FLOW IS EXPECTED TO INCREASE TO 20 KT S OF THIS LOW AND THE MONSOON TROUGH LATER TONIGHT...WITH 20-25 KT NE-E FLOW DEVELOPING N OF THE LOW AND MONSOON TROUGH BY SAT EVENING WITH SEAS BUILDING TO 9 FT BY THEN AS WELL. ENVIRONMENTAL CONDITIONS ARE GENERALLY CONDUCIVE FOR GRADUAL DEVELOPMENT OF THIS SYSTEM...AND THIS LOW HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 24 HOURS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 09N79W TO 07N82W TO 12N92W TO 1008 MB LOW PRES NEAR 09N95.5W TO 08N112W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N112W TO 10N121W THEN RESUMES FROM 09N126W TO 08N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 10N TO 13N BETWEEN 99W AND 101W. SIMILAR CONVECTION IS WITHIN 60 NM EITHER SIDE OF THE ITCZ BETWEEN 127W AND 132W...AND ALSO W OF 137W. ...DISCUSSION... AN UPPER LEVEL CYCLONIC CIRCULATION HAS MOVED INTO THE FAR NW PORTION OF THE DISCUSSION AREA NEAR 31N137W. AN ASSOCIATED UPPER LEVEL TROUGH EXTENDS FROM THE CYCLONIC CIRCULATION TO 25N140W. AN UPPER LEVEL RIDGE PRECEDES THE TROUGH WITH AN AXIS ALONG 32N127W TO AN ANTICYCLONIC CIRCULATION NEAR 14N120W. MAINLY WESTERLY ZONAL UPPER LEVEL FLOW COVERS THE WATERS N OF 15N. MID TO HIGH LEVEL MOISTURE CONTINUES TO BE ADVECTED INTO THE W REGION ACROSS THE WATERS W OF 120W WITH THE AID OF 45-65 KT WINDS ALOFT. WATER VAPOR SATELLITE IMAGERY INDICATES STRONG SUBSIDENCE WITH DRY AND STABLE AIR AT THE MID AND UPPER LEVELS ACROSS THE AREA N OF 17N E OF 120W. AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS S OF EL SALVADOR NEAR 10N89W WITH A RIDGE AXIS REACHING FROM THERE TO 12N111W. UPPER LEVEL DIFFLUENCE OVER THIS REGION IS ENHANCING CONVECTION ALONG THE MONSOON TROUGH AS DESCRIBED ABOVE. IN THE DEEP TROPICS...AN UPPER LEVEL CYCLONIC CIRCULATION IS JUST TO THE S OF THE EQUATOR WITH AN ASSOCIATED UPPER TROUGH FROM 00N121W TO 09N120W. DRY AND STABLE AIR COVERS THE WATERS S OF 06N AND W OF 93W. AT THE SURFACE...WEAKENING 1026 MB HIGH PRES IS JUST NW OF THE DISCUSSION WATERS NEAR 33N137W WITH A RIDGE EXTENDING INTO THE AREA NEAR 32N135W TO 16N108W. NW SWELL OF 8-10 FT COVERS THE AREA N OF 27N BETWEEN 119W AND 129W...AND A SHIP WITH CALL-SIGN 'WDC3786' NEAR 30N128W REPORTED SEAS TO 10 FT AT 00 UTC. THIS SWELL WILL SUBSIDE TO LESS THAN 8 FT WITHIN THE NEXT 24 HOURS. A NEW SET OF LARGE NW SWELL WITH PEAK WAVE PERIODS OF 16-18 SECONDS WILL PUSH S OF 30N EARLY SAT MORNING WITH SEAS BUILDING TO 13 FT ALONG 30N BY SAT EVENING. A WEAKENING SURFACE TROUGH IS ANALYZED ALONG THE ITCZ FROM 14N120W TO 10N126W. ISOLATED TO SCATTERED MODERATE CONVECTION IS WITHIN 60-120 NM EITHER SIDE OF THE TROUGH. AN EARLIER SCATTEROMETER PASS CAPTURED NE-E 20 KT WINDS WITHIN 180 NM NW OF THE TROUGH WITH AN AREA OF 8-9 FT SWELL ELSEWHERE FROM 11N TO 15N BETWEEN 118W AND 126W. THE TROUGH IS FORECAST TO WEAKEN AND DISSIPATE DURING THE NEXT 18 HOURS. GAP WINDS...STRONG HIGH PRES IS BUILDING IN BEHIND A COLD FRONT MOVING THROUGH THE SW GULF OF MEXICO RESULTING IN A TIGHT PRES GRADIENT ACROSS SOUTHERN MEXICO. THIS IS RESULTING IN WINDS TO GALE FORCE IN THE GULF OF TEHUANTEPEC AND A GALE WARNING IS NOW IN EFFECT THROUGH FRI AFTERNOON. $$ LEWITSKY