WDPN32 PGTW 301500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 09W (SAOLA) WARNING NR 028// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.7N 119.7E INITIAL INTENSITY: 130 KTS GEOGRAPHIC REFERENCE: 282 NM SOUTH-SOUTHWEST OF TAIPEI, TAIWAN MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 46 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 09W (SAOLA) REMAINS A SUPER TYPHOON (STY) BUT IS STARING TO SHOW SIGNS OF WEAKENING ACROSS THE SPECTRUM OF AVAILABLE DATA. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 20NM WIDE STADIUM EYE WITH EYE TEMPERATURES MAINTAINING A VERY CONSISTENT 17C OVER THE PAST SIX HOURS. ANIMATED RADAR DATA AND A 300906Z SSMIS 91GHZ IMAGE CONFIRM THREE IMPORTANT FACTS; THE EYE HAS BEGUN TO SHRINK SINCE AROUND 1100Z, THE NORTHERN EYEWALL HAS ERODED SIGNIFICANTLY OVER THE PAST SIX HOURS AND THE SECONDARY EYEWALL IS BEGINNING TO DOMINATE THE OVERALL STRUCTURE. IN TERMS OF INTENSITY, WE HAVE BEEN LUCKY TO RECEIVE TWO GOLD-STANDARD INTENSITY MEASUREMENTS IN THE LAST THREE HOURS; A 300908Z SMAP PASS REVEALED 118 KNOT 10-MIN WINDS IN THE SOUTHEASTERN QUADRANT, WHICH CONVERT TO 126 KNOT 1-MIN WINDS, AND A 301001Z RCM-3 PARTIAL SAR PASS. WHILE THE SAR DID NOT COVER THE ENTIRETY OF THE STORM, IT DID COVER THE EYE AND THE SOUTHEASTERN QUADRANT, WHERE THE HIGHEST WINDS HAVE BEEN OVER THE PAST 24 HOURS, AND REVEALED A MAXIMUM WIND OF 129 KNOTS. THUS THE INTENSITY IS SET TO 130 KNOTS WITH HIGH CONFIDENCE, REGARDLESS OF THE T7.0 DVORAK BASED ESTIMATES FROM ALL AGENCIES. 130 KNOTS IS ALSO SUPPORTED BY THE ADT, AIDT, DPRINT AND SATCON ESTIMATES. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE, HOWEVER THE ONSET OF THE EYEWALL REPLACEMENT CYCLE (EWRC) IS PROVING TO THE PRIMARY FACTOR IN THE WEAKENING OF THE SYSTEM. INITIAL WIND RADII BASIS: SAR AND SMAP DATA CURRENT STEERING MECHANISM: SOUTHWESTERN EDGE OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T7.0 - 140 KTS RJTD: T7.0 - 140 KTS RCTP: T7.0 - 140 KTS KNES: T7.0 - 140 KTS CIMSS ADT: 132 KTS AT 301130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: EYEWALL REPLACEMENT CYCLE (EWRC) ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: STY 09W WILL CONTINUE TO TRACK TOWARDS THE WEST-NORTHWEST FOR THE NEXT 24 HOURS ALONG THE SOUTHWEST SIDE OF THE STR FAR TO THE NORTHEAST. THE PRIMARY STEERING INFLUENCE RAPIDLY SHIFTS TO A TRANSIENT ANTICYCLONE WHICH PASSES TO THE NORTH IN THE WAKE OF A DEEP, MID-LATITUDE TROUGH THAT WILL SWING EAST THROUGH CENTRAL CHINA OVER THE NEXT DAY. STY 09W WILL TURN WESTWARD BETWEEN TAU 36 AND TAU 48 UNDER THE INFLUENCE OF THIS TRANSIENT ANTICYCLONE. FROM AN INTENSITY PERSPECTIVE, THE SYSTEM WILL SLOWLY BUT STEADILY WEAKEN THROUGH TAU 48 FIRST IN RESPONSE TO THE ONGOING EWRC, FROM WHICH THE SYSTEM WILL NOT HAVE TIME TO RECOVER, AND SECOND IN RESPONSE TO AN EXPECTED UPTICK IN SOUTHERLY WIND SHEAR AFTER TAU 36. AFTER TAU 48, THE INFLUENCE OF A DRY AIR ENTRAINING INTO THE CORE OF THE SYSTEM, INCREASED VERTICAL WIND SHEAR AND DISRUPTION OF THE LOW-LEVEL FLOW DUE TO TERRAIN INTERACTION, WILL LEAD TO A FASTER PACE OF WEAKENING. AS THE SYSTEM QUICKLY WEAKENS AS IT PASSES SOUTH OF HONG KONG, THE STEERING LEVEL WILL STEADILY PROGRESS TO LOWER LEVELS OF THE ATMOSPHERE, WHERE THE STEERING GRADIENT WILL BE MUCH WEAKER AS A WEAKNESS IN THE STEERING PATTERN DEVELOPS. AS THE SYSTEM WEAKENS BELOW TROPICAL STORM STRENGTH, IT WILL COME UNDER THE STEERING INFLUENCE OF THE LOW TO MID-LEVEL SOUTHWESTERLY MONSOONAL FLOW, AND TURN SHARPLY BACK TOWARDS THE EAST-NORTHEAST BY THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS BEGINNING TO SHOW INCREASED UNCERTAINTY, AS THE MODELS DEPICT DIFFERENCES IN THE PATTERN EVOLUTION. THROUGH TAU 48, THE BULK OF THE GUIDANCE IS CONSISTENT WITH THE EARLIER RUN, WITH THE ECMWF CONTINUING TO MARK THE NORTHERN EDGE OF THE ENVELOPE, TAKING THE SYSTEM INLAND EAST OF HONG KONG AROUND TAU 48 AND THEN SKIRTING THE COASTLINE THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE GFS MEANWHILE REMAINS THE SOUTHERN EDGE MARKER, BUT WITH THIS RUN INTRODUCES THE SHARP TURN BACK TO THE EAST AFTER TAU 72, AS DOES THE NAVGEM AND TO A LESSER DEGREE, THE GEFS ENSEMBLE MEAN. THE GFS IS PARTICULARLY FAST IN TURNING THE SYSTEM AND RACING IT OFF TO THE NORTHEAST, NEARING THE SOUTHERN TAIWAN STRAIT BY TAU 120. THE JTWC FORECAST LIES CLOSE TO THE CONSENSUS MEAN THROUGH THE FORECAST. CONFIDENCE IS HIGH TO ABOUT TAU 48, BUT LOW THEREAFTER DUE TO THE LARGE SPREAD DEPICTED IN THE GUIDANCE AFTER TAU 72. INTENSITY GUIDANCE IS IN VERY GOOD AGREEMENT, WITH ALL MODELS INDICATING STEADY WEAKENING THROUGH THE FORECAST PERIOD. THE JTWC FORECAST LIES ON THE HIGHER END OF THE ENVELOPE WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN