WDPN31 PGTW 250900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MINDULLE) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.6N 137.6E INITIAL INTENSITY: 90 KTS GEOGRAPHIC REFERENCE: 467 NM WEST OF AGRIHAN MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 32 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A QUICKLY DEVELOPING SYSTEM WITH A NASCENT EYE FEATURE BEGINNING TO SHOW ITSELF BY THE 0600Z HOUR. SUBSEQUENT IMAGERY INDICATES THE DEVELOPMENT OF A RAGGED, COLD, CLOUD-FILLED EYE BY THE 0700Z HOUR, INDICATIVE OF THE ONSET OF THE LONG-AWAITED RAPID INTENSIFICATION PHASE. THE SYSTEM HAS BECOME MUCH MORE SYMMETRICAL AND MOIST OVER THE PAST SIX HOURS, WITH THE MOST RECENT TOTAL PRECIPITABLE WATER (TPW) LOOPS INDICATING THE PREVIOUS DRY-SLOT TO THE SOUTH IS NO LONGER PRESENT, REMOVING ONE LAST IMPEDIMENT TO THE RAPID INTENSIFICATION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE NASCENT EYE IN THE ENHANCED INFRARED AND MSI. THE INITIAL INTENSITY IS ASSESSED AT 90 KNOTS WITH MEDIUM CONFIDENCE BASED ON THE AVERAGE OF AGENCY CURRENT INTENSITY ESTIMATES BETWEEN T5.0-5.5 (77-102 KNOTS). THE OBJECTIVE ADT AND SATCON ESTIMATES CONTINUE TO BE UNREALISTICALLY LOW AND ARE DISCOUNTED. TYPHOON 20W IS MOVING RELATIVELY SLOWLY NORTHWESTWARD THROUGH A COMPLEX STEERING ENVIRONMENT, WITH A NEAR-EQUATORIAL RIDGE TO THE SOUTH, A STRONG SUBTROPICAL RIDGE (STR) CENTERED NEAR SHANGHAI WITH AN EXTENSION EXTENDING EAST ALONG THE 30TH LATITUDE TO NEAR 150E AND A DEVELOPING MID-LEVEL RIDGE TO THE EAST OF THE MARIANAS. THE NET RESULT IS A GENERAL SLOW-DOWN IN THE FORWARD TRACK MOTION. THE ENVIRONMENT IS HIGHLY CONDUCIVE TO RAPID INTENSIFICATION WITH VERY WARM (31C) SSTS, ROBUST RADIAL OUTFLOW AND LOW VWS. OCEAN HEAT CONTENT (OHC) REMAINS HIGH FOR THE NEAR-TERM. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: COMPLEX STEERING ENVIRONMENT, WITH A NEAR-EQUATORIAL RIDGE TO THE SOUTH, A STRONG SUBTROPICAL RIDGE (STR) CENTERED NEAR SHANGHAI WITH AN EXTENSION EXTENDING EAST ALONG THE 30TH LATITUDE TO NEAR 150E AND A DEVELOPING MID-LEVEL RIDGE TO THE EAST OF THE MARIANAS. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS RJTD: T5.0 - 90 KTS RCTP: T5.0 - 90 KTS KNES: T5.5 - 102 KTS CIMSS SATCON: 78 KTS AT 250404Z CIMSS ADT: 61 KTS AT 250540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TYPHOON 20W IS ENTERING A COMPLEX STEERING ENVIRONMENT, CHARACTERIZED BY THE INTERACTIONS BETWEEN MULTIPLE RIDGE COMPLEXES. THE STRONG STR CENTERED NEAR SHANGHAI IS EXTENDING EAST ALL THE WAY TO THE 150E LONGITUDE LINE, AND WILL SERVE AS A BRAKE ON THE POLEWARD MOTION THROUGH TAU 48. AT THE SAME TIME A BUILDING MID- TO HIGH-LEVEL RIDGE WILL BUILD TO THE EAST, AND AS IT STRENGTHENS, WILL PUSH TY 20W SLOWLY TOWARDS THE NORTHWEST. THE COMPETING NATURE OF THE STEERING PATTERN WILL RESULT IN SLOW (04 KNOTS OR LESS) MOVEMENT GENERALLY TOWARDS THE NORTHWEST, THOUGH PERIOD OF NEAR-QUASISTATIONARY MOTION OVER THE NEXT 24 TO 48 HOURS IS NOT OUT OF THE REALM OF POSSIBILITY, ESPECIALLY IF THE RIDGE TO THE NORTH BUILDS MORE THAN CURRENTLY ANTICIPATED. BY TAU 72 A SERIES OF TRANSITORY MID-LATITUDE TROUGHS WILL BREAK THE RIDGE TO THE NORTH, ALLOWING TY 20W TO BREAK OUT, AND ACCELERATE NORTHEASTWARD ALONG THE NORTHWEST PERIPHERY OF THE STR TO ITS SOUTHEAST AND AHEAD OF AN APPROACHING DEEP MID-LATITUDE TROUGH. THE SYSTEM IS EXPECTED TO RAPIDLY INTENSIFY OVER THE NEXT 24 TO 36 HOURS AS IT REMAINS OVER RELATIVELY HIGH OHC WATERS, PEAKING AT 130 KNOTS BY TAU 36. BY THAT POINT IT WILL BEGIN MOVING OVER A POOL OF LOWER OHC WATERS, LEADING TO UPWELLING OF SIGNIFICANTLY COOLER WATERS, WHICH WILL SERVE TO IMPEDE ADDITIONAL INTENSIFICATION EVEN IN THE PRESENCE OF OTHERWISE NEAR-IDEAL CONDITIONS. AFTER MAKING ITS TURN NORTHEAST, INCREASING MID-LEVEL VWS AND DECREASING SSTS WILL LEAD TO STEADY WEAKENING THROUGH THE REMAINDER OF THE FORECAST PERIOD. MODEL DISCUSSION: THE SPREAD IN THE TRACK GUIDANCE HAS SHOWN A MARKED INCREASE SINCE THE PREVIOUS RUN, ESPECIALLY AFTER TAU 36. IN THE NEAR-TERM THE GUIDANCE IS IN GOOD AGREEMENT ON BOTH TRACK AND SPEED. AFTER TAU 36, THE UKMET, UKMET ENSEMBLE, ECMWF AND NAVGEM DEPART FROM THE REMAINDER OF THE GUIDANCE AND SHOW A SHARP TURN TO THE WEST-NORTHWEST, TAKING THE SYSTEM TO NEAR 133E BEFORE RECURVING AND COMING INTO TIGHTER AGREEMENT WITH THE REST OF THE PACK. THE GFS AND ITS ENSEMBLE MEANWHILE INDICATE A SHARPER AND FASTER TURN, INSIDE THE REMAINDER OF THE GUIDANCE, WITH A SPREAD OF 140 NM AT TAU 72 INCREASING TO 350 NM BY TAU 120. THE JTWC TRACK LIES CLOSE TO THE BULK OF GUIDANCE THROUGH TAU 48, THEN SHIFTS WEST OF THE CONSENSUS IN LIGHT OF THE EUROPEAN TRACKERS THROUGH THE REMAINDER OF THE FORECAST. INTENSITY GUIDANCE IS A MIXED BAG, WITH THE HWRF BEING A SIGNIFICANT OUTLIER, DECREASING INTENSITY FROM THE START BEFORE INTENSIFYING ONCE AGAIN, BUT ONLY REACHING A PEAK OF 100 KNOTS. CLEARLY BASED ON RECENT SATELLITE TRENDS, THIS IS NOT A REALISTIC SCENARIO. THE REMAINDER OF THE MESOSCALE MODELS ALSO DEPICT A MUCH WEAKER STORM PEAKING NEAR 115 KNOTS. MEANWHILE, THE RAPID INTENSIFICATION PREDICTION AID (RIPA) AND ITS CONSTITUENTS HAVE TRIGGERED ON THIS RUN, WHICH SUPPORTS THE SHIPS GUIDANCE. THE JTWC FORECAST LIES CLOSE TO THE RIPA THROUGH TAU 24, THEN LEVELS OFF WELL ABOVE THE CONSENSUS THROUGH TAU 96. DUE TO THE UNCERTAINTIES ASSOCIATED WITH THE RAPID INTENSIFICATION, THE POTENTIAL OF EYEWALL REPLACEMENT CYCLES AND THE IMPACT OF THE LOW OHC POOL THAT LIES ALONG THE TRACK, THERE IS LOW CONFIDENCE IN THE INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN