000 AXPZ20 KNHC 301535 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1630 UTC THU AUG 30 2012 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1500 UTC. ...SPECIAL FEATURES... HURRICANE ILEANA CENTERED NEAR 20.2N 113.7W AT 30/1500 UTC OR 305 MILES SW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MOVING NW AT 7 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB. MAXIMUM SUSTAINED WIND SPEED IS 70 KT WITH GUSTS TO 85 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. SCATTERED MODERATE AND ISOLATED STRONG CONFECTION IS WITHIN 120 NM IN THE NE SEMICIRCLE OF ILEANA. SCATTERED TO NUMEROUS STRONG CONVECTION IS WITHIN 150 NM IN THE SW SEMICIRCLE OF ILEANA. ILEANA IS FORECAST TO BEGIN TO MOVE OVER COOLER SEA SURFACE TEMPERATURES DURING THE NEXT FEW DAYS AND THUS IT IS FORECAST TO WEAKEN TO A TROPICAL STORM FRI NIGHT NEAR 22.5N 116.4W AS IT CONTINUES TO TRACK IN A NW DIRECTION. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 09N78W TO 11N89W TO 11N104W THEN RESUMES FROM 16N114W TO 11N120W TO 11N140W. NO INTERTROPICAL CONVERGENCE ZONE AXIS IS EVIDENT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 300 NM S OF THE MONSOON TROUGH E OF 90W...AND 180-210 NM S OF THE MONSOON TROUGH BETWEEN 90W AND 105W. SIMILAR CONVECTION IS WITHIN 180 NM N OF THE MONSOON TROUGH E OF 105W. ...DISCUSSION... AN UPPER LEVEL TROUGH IS MOVING OVER THE NW COAST OF THE CONUS REACHING FROM THE SAN FRANCISCO BAY AREA OF CALIFORNIA SW INTO THE AREA NEAR 32N127W TO 27N133W. AN UPPER LEVEL WESTERLY JET WITH 50-70 KT WIND SPEEDS IS NEAR OR JUST TO THE W OF THE TROUGH AXIS. AN UPPER LEVEL ANTICYCLONE IS POSITIONED OVER 17N132W WITH AN UPPER RIDGE AXIS REACHING NW OF THE AREA TO 32N150W. MAINLY DRY AND STABLE AIR COVERS THE DISCUSSION WATERS W OF A LINE FROM CENTRAL BAJA CALIFORNIA TO 00N140W. AN UPPER LEVEL ANTICYCLONE IS OVER CENTRAL TEXAS WITH ANTICYCLONIC FLOW ALOFT PRESENT ON THE SW PERIPHERY OF THIS ANTICYCLONE OVER MEXICO. ANOTHER ANTICYCLONE IS E-SE OF ILEANA NEAR 18N108W WITH A RIDGE AXIS EXTENDING N-NW TO ACROSS THE SOUTHERN HALF OF THE BAJA CALIFORNIA PENINSULA. MOST OF THE DEBRIS MOISTURE FROM ILEANA IS ADVECTED SW TO 10N E OF 120W. ADDITIONAL DEBRIS MOISTURE IS ALSO FANNING OUT IN THE UPPER ANTICYCLONIC FLOW N OF ILEANA ACROSS THE SOUTHERN BAJA PENINSULA AND GULF OF CALIFORNIA. AN UPPER LEVEL CYCLONE IS QUASI-STATIONARY OVER THE NW CARIBBEAN NEAR THE CAYMAN ISLANDS WITH AN UPPER TROUGH EXTENDING SW TO ACROSS NICARAGUA. A WEAK UPPER RIDGE IS TO THE S-SE FROM EASTERN PANAMA TO 16N81W. UPPER LEVEL EASTERLY FLOW COVERS THE WATERS E-SE OF ILEANA. AT THE SURFACE...SOUTHWESTERLY MONSOONAL FLOW AT 20-25 KT WINDS WITH SEAS 8 TO 11 FT ARE OBSERVED WITHIN 120 NM EITHER SIDE OF A LINE FROM 19N109W TO 11N116W TO THE SE OF HURRICANE ILEANA. THIS FLOW WILL GRADUALLY WEAKEN TO LESS THAN 20 KT BY SAT MORNING AS ILEANA MOVES POLEWARD. A SMALL AREA OF 8 FT MIXED NE AND S SWELL IS IN THE FAR W CENTRAL PORTION OF THE DISCUSSION AREA FROM 12N TO 16N W OF 136W GENERATED BY EARLY FRESH NE TRADES. THIS SWELL IS FORECAST TO DECAY TO LESS THAN 8 FT BY FRI MORNING. LONG PERIOD SOUTHERLY CROSS-EQUATORIAL SWELL TO 9 FT WITH PEAK WAVE PERIOD OF 15-18 SECONDS COVERS AN AREA BOUNDED BY 00N135W TO 10N130W TO 10N100W TO 00N92W TO 00N135W. THIS SWELL WILL GRADUALLY DECAY TO 8 FT THROUGH SAT MORNING WHILE LONG PERIOD SURF CONTINUES TO REACH AND IMPACT THE COASTLINES OF MEXICO AND CENTRAL AMERICA. GLOBAL MODEL GUIDANCE CONTINUES TO CONSISTENTLY SUGGEST THAT A 1009 MB SURFACE LOW WILL FORM ALONG THE MONSOON TROUGH NEAR 11.5N91W BY FRI MORNING...WITH CYCLONIC WINDS OF 20 TO 25 KT GRADUALLY EXPANDING OUT TO 240 NM IN THE N QUADRANT AND 300 NM IN THE S QUADRANT. ASSOCIATED SEAS OF 8 TO 10 FT WILL MIX WITH LONG PERIOD CROSS EQUATORIAL SW SWELL AT 16 TO 19 SECONDS WHICH WILL COVER THE WATERS S OF CENTRAL AMERICA BETWEEN 90W AND 100W. THIS LOW WILL MOVE TO 13N93W BY SAT MORNING WHILE GRADUALLY INTENSIFYING THROUGH THE WEEKEND. $$ LEWITSKY