000 AXPZ20 KNHC 172143 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU NOV 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 09N79W TO 1009 MB LOW PRES NEAR 09N94.5W TO 09N112W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N112W TO 11N120W THEN RESUMES FROM 10N126W TO 08N135W TO 09N140W. SCATTERED MODERATE CONVECTION IS FROM 05N TO 09N E OF 85W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 10N TO 13N BETWEEN 94W AND 100W...AND WITHIN 60 NM EITHER SIDE OF THE MONSOON TROUGH BETWEEN 94W AND 99W. SIMILAR CONVECTION IS WITHIN 45 NM EITHER SIDE OF THE ITCZ BETWEEN 130W AND 134W...AND ALSO W OF 138W. ...DISCUSSION... AN UPPER LEVEL CYCLONIC CIRCULATION HAS MOVED INTO THE FAR NW PORTION OF THE DISCUSSION AREA NEAR 31N139W. AN ASSOCIATED UPPER LEVEL TROUGH EXTENDS FROM THE CYCLONIC CIRCULATION TO 24N140W. AN UPPER LEVEL RIDGE PRECEDES THE TROUGH WITH AN AXIS ALONG 32N128W TO AN ANTICYCLONIC CIRCULATION NEAR 13N123W. 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 A 50-70 KT JET CORE. WATER VAPOR SATELLITE IMAGERY INDICATES STRONG SUBSIDENCE WITH DRY AND STABLE AIR AT THE MID AND UPPER LEVELS ACROSS THE AREA N OF 16N E OF 120W. AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS S OF GUATEMALA AND EL SALVADOR NEAR 10N90W WITH A RIDGE AXIS REACHING FROM THERE TO 12N113W. 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 00N120W TO 10N115W. DRY AND STABLE AIR COVERS THE WATERS S OF 06N AND W OF 90W. AT THE SURFACE...1030 MB HIGH PRES IS NW OF THE AREA NEAR 36N146W WITH A RIDGE EXTENDING INTO THE DISCUSSION AREA NEAR 32N135W TO 18N109W. AN 1800 UTC ENVISAT ALTIMETER PASS INDICATED 8-9 FT SEAS IN NW SWELL N OF 26N BETWEEN 120W AND 126W. 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 LATE FRI NIGHT WITH SEAS BUILDING TO 12 FT ALONG 30N BY SAT AFTERNOON. A 1009 MB AREA OF LOW PRES IS EMBEDDED IN THE MONSOON TROUGH NEAR 09N94.5W IS DRIFTING W. ASSOCIATED CONVECTION IS DESCRIBED IN THE SECTION ABOVE. SW FLOW IS EXPECTED TO INCREASE TO 20 KT S OF THIS LOW AND THE MONSOON TROUGH IN LATE TONIGHT AND FRI...WITH 20 KT NE-E FLOW DEVELOPING N OF THE LOW AND MONSOON TROUGH BY SAT AFTERNOON WITH SEAS BUILDING TO 9 FT BY THEN AS WELL. A SURFACE TROUGH IS ANALYZED ALONG THE ITCZ FROM 14N122W TO 08N123W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 08N TO 10N BETWEEN 118W AND 124W. A 1726 UTC ASCAT SCATTEROMETER PASS CAPTURED NE-E 20 KT WINDS FROM 12N TO 16N BETWEEN 119W AND 125W...AND A 1820 UTC ENVISAT ALTIMETER PASS INDICATED 8 FT SEAS IN THAT AREA AS WELL. THE TROUGH IS FORECAST TO WEAKEN AND DISSIPATE BY 24 HOURS WITH WINDS AND SEAS DIMINISHING AND SUBSIDING TOMORROW AFTERNOON. GAP WINDS...STRONG HIGH PRES WILL BUILD IN BEHIND A COLD FRONT MOVING THROUGH THE SW GULF OF MEXICO RESULTING IN A TIGHT PRES GRADIENT ACROSS SOUTHERN MEXICO. THIS WILL RESULT IN WINDS INCREASING TO GALE FORCE IN THE GULF OF TEHUANTEPEC COMMENCING THIS EVENING...THEN DIMINISHING BELOW GALE FORCE BY FRI AFTERNOON. $$ LEWITSKY