000 AXPZ20 KNHC 012206 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC SAT SEP 01 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC. ...SPECIAL FEATURES... TROPICAL STORM ILEANA...CENTERED AT 23.1N 119.7W AT 01/2100 UTC. ILEANA IS MOVING W OR 275 DEG AT 09 KT WITH AN ESTIMATED MINIMUM CENTRAL PRESSURE OF 1003 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SCATTERED MODERATE CONVECTION IS NOTED WITHIN 90 NM NW AND WITHIN 60 NM SE SEMICIRCLES OF CENTER. THE CYCLONE IS MOVING OVER INCREASINGLY COOLER SEAS SURFACE WATERS AND MORE STABLE ATMOSPHERIC CONDITIONS AND IS EXPECTED TO WEAKEN TO A REMNANT LOW PRES TONIGHT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. TROPICAL LOW...A COUPLE OF SURFACE LOWS ARE ANALYZED AT 1800 UTC. ONE LOW PRES IS ALONG THE MONSOON TROUGH AT 12N103.5W AND IS ESTIMATED AT 1010 MB WITH SCATTERED MODERATE TO STRONG CONVECTION CURRENTLY OBSERVED WITHIN 300 NM OVER THE NW QUADRANT OF CENTER. THE SECOND LOW PRESSURE IS ANALYZED AT 16.5N102W AND IS ESTIMATED AT 1007 MB WITH SCATTERED STRONG CONVECTION CURRENTLY NOTED WITHIN 90 NM OF THE CENTER. SHIP DDBB2 AT 17N102W REPORTED 1006.5 MB BUT HISTORY ON THIS SHIPS OBSERVATIONS INDICATE A 2 MB LOW BIAS...THUS THE ANALYZED PRESSURE OF 1007 MB. GLOBAL GUIDANCE SUGGESTS THAT THESE SURFACE LOWS WILL MERGE NEAR 15N107W ON SUN AND CONTINUE NW TO NEAR 18N113W ON MON WITH TROPICAL CYCLONE DEVELOPMENT LIKELY DURING THE 48 HOUR PERIOD. CURRENTLY THE PRESSURE GRADIENT BETWEEN STRONG HIGH PRESSURE BRIDGING SW ACROSS CENTRAL AMERICA AND LOW PRESSURE WITHIN THE BROAD MONSOON TROUGH HAS ENHANCED EASTERLY WINDS TO 20 TO 30 KT WITHIN 120 NM EITHER SIDE OF A LINE FROM 18N105W TO 14N98W. THE GRADIENT IS ALSO TIGHT OVER S SEMICIRCLE OF THE SOUTHERNMOST SURFACE LOW AND S TO SW WINDS ARE AT 20 TO 25 KT WITH SEAS 9 TO 10 FT WITHIN THE AREA FROM 10N TO 12N BETWEEN 98W AND 113W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W FROM THE AT THE PANAMA/COLOMBIAN BORDER ACROSS N PANAMA TURNING THEN CONTINUING NW ALONG THE PACIFIC COASTS OF COSTA RICA...NICARAGUA...EL SALVADOR AND HONDURAS...THEN TURNING SW INTO AN EMBEDDED LOW PRESSURE NEAR 12N103.5W. THE MONSOON TROUGH THEN TURNS NW TO 15N109W...THEN SW TO 10N125W TO BEYOND 10N140W. ISOLATED MODERATE AND STRONG CONVECTION IS OBSERVED TO THE N OF 03N BETWEEN 80W AND 100W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED ELSEWHERE FROM 09N TO 16N BETWEEN 103W AND 114W. ...DISCUSSION... A LONG WAVE UPPER TROUGH DOMINATES THE EASTERN N PACIFIC WITH AN EMBEDDED SHORTWAVE TROUGH BECOMING SLIGHTLY NEGATIVE TILT OVER THE DISCUSSION AREA FROM 32N128W TO 25N125W. IMMEDIATELY TO THE SW AN UPPER LEVEL ANTICYCLONE IS CENTERED AT 22N138W WITH A RIDGE EXTENDING E TO A SHARP CREST AT 24N123W. ANOTHER UPPER ANTICYCLONE IS OVER THE MEXICO/TEXAS BORDER NEAR 31N107W WITH A RIDGE EXTENDING SW TO A SHARP CREST AT 25N120W...WHICH IS JUST N OF THE DISSIPATING TROPICAL CYCLONE ILEANA. SOME OF THE DEBRIS MOISTURE FROM ILEANA CONCENTRATES INTO A 360 NM WIDE PLUME EXTENDING SW TO NEAR 13N135W WHERE IT ALMOST EVAPORATES. SOME OF THE TROPICAL CYCLONE DEBRIS MOISTURE IS STILL EVIDENT ALONG A NARROW LINE FROM EXTREME NORTHERN BAJA CALIFORNIA PENINSULA THEN FANNING OUT ACROSS MOST OF ARIZONA AND WESTERN NEW MEXICO. OTHERWISE THE UPPER LEVELS ARE FAIRLY DRY N OF 20N W OF 123W AND FROM 17N TO 20N W OF 130W. AN UPPER TROUGH ORIGINATING IN THE CENTRAL N ATLANTIC CONTINUES SW ACROSS THE NW CARIBBEAN TO BASE OVER THE TROPICAL E PACIFIC AT 13N88W. AN AREA OF UPPER DIFFLUENCE IS INDUCED OVER THE SW CARIBBEAN AND OVER SOUTHERN PORTIONS OF CENTRAL AMERICA. THE RESULTANT DENSE UPPER DEBRIS MOISTURE IS ADVECTED SW MERGING WITH THE ADDITIONAL DEBRIS MOISTURE ORIGINATING FROM THE TROPICALS LOWS...WITH THE SOUTHERN EXTENT OF THE MOISTURE ALONG 03N BETWEEN 80W AND 110W. ELSEWHERE AT THE LOW LEVELS...SURFACE HIGH PRESSURE IS CENTERED N OF THE AREA NEAR 35N148W AND IS PRODUCING LIGHT TO MODERATE NE FLOW ACROSS THE AREA W OF TROPICAL CYCLONE ILEANA. $$ NELSON