000 AXPZ20 KNHC 142141 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC FRI OCT 14 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 2015 UTC. ...SPECIAL FEATURES... TROPICAL STORM IRWIN CENTERED NEAR 18.0N 106.9W AT 14/2100 UTC OR 185 MI W-SW OF MANZANILLO MEXICO MOVING S OR 180 DEG AT 4 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC FORECAST /ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS. NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 90 NM IN THE SW SEMICIRCLE OF IRWIN...WITH SCATTERED MODERATE CONVECTION FROM 16N TO 19N BETWEEN 105W AND 110W...AND ALSO FROM 19N TO 21N BETWEEN 107W AND 109W. LITTLE CHANGE IN STRENGTH IS EXPECTED THROUGH 72 HOURS AS IRWIN MOVES S-SW...WITH WEAKENING TO A TROPICAL DEPRESSION FORECAST FROM 96-120 HOURS AS IRWIN TURNS MORE TO THE W-NW AND ENCOUNTERS COOLER WATERS AND DRIER AND MORE STABLE AIR ALOFT. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM A 1005 MB LOW PRES OVER GUATEMALA NEAR 16N89W TO 14N100W THEN RESUMES WELL TO THE SW OF TROPICAL STORM IRWIN FROM 1010 MB LOW PRES NEAR 12N123W TO 09N140W. NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 12N TO 16N BETWEEN 96W AND 99W. SOUTH OF THE MONSOON TROUGH...SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS N OF 12N BETWEEN 88W AND 93W. SCATTERED MODERATE CONVECTION IS FROM 10N TO 12N BETWEEN 98W AND 103W. ...DISCUSSION... A COLD FRONT IS IN THE NW PORTION OF THE WATERS EXTENDING FROM 30N136W TO 27N140W. A 1534 UTC WINDSAT SCATTEROMETER PASS INDICATED 20-25 KT NW WINDS BEHIND THE FRONT WITH HIGHER WINDS W OF THE AREA. SEAS ARE ALSO RUNNING UP TO 10 FT IN NW SWELL IN THIS SAME AREA. BY 24 HOURS...A RATHER SIGNIFICANT 1006 MB AREA OF LOW PRES WILL BE JUST N OF THE AREA NEAR 31N138W WITH A WEAKENING COLD FRONT EXTENDING FROM THE LOW INTO THE AREA FROM 30N134W TO 20N140W. MODEL GUIDANCE CONTINUES THE 20-25 KT WINDS BEHIND THE FRONT WHILE SEAS BUILD TO BETWEEN 9-14 FT IN NW SWELL. THE SWELL WILL ALSO PROPAGATE S REACHING TO 20N BETWEEN 110W AND 117W IN 24 HOURS. THE LOW WILL WEAKEN TO 1008 MB AS IT MOVES TO NEAR 31N136W IN 48 HOURS WITH THE REMNANT FRONT REACHING FROM THE LOW INTO THE AREA FROM 30N130W TO 25N131W TO 18N140W. WINDS WILL DIMINISH TO LESS THAN 20 KT IN 48 HOURS WHILE LINGERING NW SWELL RANGES FROM 8-12 FT BEHIND THE FRONT. 1010 MB LOW PRES IS EMBEDDED IN THE MONSOON TROUGH NEAR 12N123W. AN EARLIER WINDSAT SCATTEROMETER PASS JUST MISSED THE LOW ALTHOUGH MODEL GUIDANCE CONTINUES TO INDICATE 20 KT SOUTHERLY WINDS WITHIN 90 NM IN THE SE SEMICIRCLE OF THE LOW AND S OF THE MONSOON TROUGH WITH SEAS OF 8-11 FT IN MERGING SW AND NW SWELL. THE LOW DISSIPATES IN 24 HOURS WHILE THE LEFT-OVER AREA OF SWELL MERGES WITH THE BROAD AREA OF MIXED SWELL ASSOCIATED WITH T.S. IRWIN. AN EARLIER WINDSAT SCATTEROMETER PASS INDICATED 20-25 KT NORTHERLY WINDS IN AND DOWNSTREAM OF THE GULF OF TEHUANTEPEC AROUND A BROAD AREA OF 1005 MB LOW PRES CENTERED OVER CENTRAL GUATEMALA ALONG WITH 8-11 FT SEAS IN THE GULF OF TEHUANTEPEC. AN AREA OF SW 20-25 KT WINDS EXIST S-SE OF THE MONSOON TROUGH OFF THE COASTS OF CENTRAL AMERICA ELSEWHERE N OF 07N E OF 95W...AND FROM 03N TO 07N BETWEEN 78W AND 90W WHERE SEAS ARE UP TO 14 FT IN THIS AREA OF PERSISTENT SW FETCH. THESE WINDS AND SEAS WILL PERSIST OVER THE SAME GENERAL AREA FROM 24-48 HOURS AS THE BROAD AREA OF LOW PRES REMAINS NEARLY STATIONARY. AS THIS LOW PRES AREA OVER GUATEMALA LINGERS...VERY HEAVY RAINFALL WILL CONTINUE OVER PORTIONS OF THE PACIFIC COASTS OF SOUTHEASTERN MEXICO...GUATEMALA...EL SALVADOR...SOUTHERN HONDURAS AND NICARAGUA RESULTING IN LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. THE REMAINDER OF THE DISCUSSION WATERS ARE DOMINATED BY MERGING NW AND SW SWELL. THIS SWELL WILL GRADUALLY SUBSIDE FROM THE NW TO SE THROUGH THE NEXT 24-48 HOURS...WHILE THE NEW SET OF NW SWELL ENTERING THE AREA MOVES SE. $$ LEWITSKY