WDPN31 PGTW 020900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (NYATOH) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.3N 135.8E INITIAL INTENSITY: 90 KTS GEOGRAPHIC REFERENCE: 560 NM WEST-NORTHWEST OF NAVSTA GUAM MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 30 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAGGED 35NM EYE WITH IMPROVED OVERALL CONVECTIVE STRUCTURE. THIS IMPROVEMENT IS EVIDENT IN ENHANCED INFRARED SATELLITE IMAGERY AND A 020700Z GMI 89GHZ MICROWAVE IMAGE SHOWING DEEP CONVECTIVE BANDING WRAPPING TIGHTLY INTO A WELL-DEFINED MICROWAVE EYE FEATURE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE GMI IMAGE. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW AND KNES DVORAK ESTIMATES AND THE CIMSS ADT ESTIMATE, HEDGED SLIGHTLY HIGHER THAN THE CIMSS SATCON ESTIMATE. ADT ESTIMATES HAVE COME INTO BETTER AGREEMENT OVER THE PAST SIX HOURS WITH RAW T NUMBERS CURRENTLY AT 5.7 (ABOUT 105 KNOTS) USING AN EYE SCENE. UPPER-LEVEL OUTFLOW REMAINS ROBUST WITH A STRONG POLEWARD OUTFLOW CHANNEL. HOWEVER, VERTICAL WIND SHEAR (VWS) VALUES HAVE INCREASED TO 15 KNOTS WITH SIGNIFICANT DRY AIR PRESENT OVER THE WESTERN SEMICIRCLE. INITIAL WIND RADII BASIS: PARTIAL (WESTERN SEMICIRCLE) 020451Z AMSR2 WINDSPEED PRODUCT. CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE POSITIONED TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS RJTD: T4.5 - 77 KTS KNES: T5.0 - 90 KTS CIMSS SATCON: 86 KTS AT 020430Z CIMSS ADT: 90 KTS AT 020740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: DRY AIR ENTRAINMENT. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: AFTER STRUGGLING TO FORM AN EYE OVER THE PAST 12 HOURS, TY 27W HAS FORMED A RAGGED 35NM EYE, WHICH HAS LED TO AN INCREASE IN DVORAK ESTIMATES AND ADT ESTIMATES. TY 27W SHOULD BE ABLE TO INTENSIFY TO A PEAK OF 100 KNOTS BY TAU 12 AS IT TRACKS STEADILY POLEWARD. AFTER TAU 12, THE SYSTEM WILL BEGIN INTERACTING WITH THE WESTERLIES ON THE SOUTHEASTERN PERIPHERY OF A DEEP MAJOR SHORTWAVE TROUGH WITH VWS VALUES INCREASING TO 30-40 KNOTS AND SIGNIFICANT DRY AIR ENTRAINMENT, WHICH WILL LEAD TO A FAIRLY RAPID WEAKENING TREND FROM TAU 24 TO TAU 72. THE SYSTEM SHOULD CONTINUE TO TRACK NORTHEASTWARD THROUGH TAU 48 BUT WILL STALL AND TURN SHARPLY EQUATORWARD UNDER THE LOW-LEVEL NORTHEASTERLIES BY TAU 72. TY 27W WILL DISSIPATE BY TAU 72 DUE TO VERY STRONG VWS EXCEEDING 50 KNOTS AND SIGNIFICANT DRY AIR ENTRAINMENT. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 48 THEN DIVERGES WITH THE BULK OF THE MODELS INDICATING A SHARP EQUATORWARD TRACK CHANGE. HOWEVER, THERE ARE SIGNIFICANT DIFFERENCES IN THE STALL POINT AND TIMING OF THE SOUTHWARD TURN. THE BULK OF THE ECMWF (EPS) AND GFS (GEFS) ENSEMBLE SOLUTIONS SUPPORT THE JTWC FORECAST TRACK SCENARIO, HOWEVER, DUE TO THE UNCERTAINTY IN THE EXACT TIMING OF THE TURN THERE IS MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN