WDPN31 PGTW 230300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SAUDEL) WARNING NR 019// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.0N 142.3E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 861 NM EAST-SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS SIGNIFICANT WAVE HEIGHT: 45 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PINHOLE EYE FEATURE, THOUGH THE EYE IS SLIGHTLY LARGER IN BOTH THE ENHANCED INFRARED (EIR) AND RECENT MICROWAVE IMAGERY. THE MSI SHOWS THE SMALL EYE SURROUNDED BY STRONG VORTICAL HOT TOWERS (VHTS) RAPIDLY DEVELOPING ALONG THE WESTERN FLANK OF THE EYE AND WRAPPING UPSHEAR TO THE EASTERN SIDE. HOWEVER, BEYOND THE DEVELOPING EYEWALL LIES AN OBVIOUS MOAT, DENOTING A WEDGE OF DRY AIR WHICH HAS WRAPPED ITS WAY AROUND THE INNER CORE, AS PART OF THE ONGOING EYEWALL REPLACEMENT CYCLE (ERC). A 222348Z GMI COLOR-ENHANCED 89GHZ IMAGE DEPICTS A FRAGMENTED INNER EYEWALL, OPEN ACROSS THE NORTHERN SEMICIRCLE, WITH A VERY WELL-DEFINED MOAT WRAPPING COUNTER-CLOCKWISE FROM SOUTHEAST TO WEST OF THE MICROWAVE EYE FEATURE, WITH A SECONDARY EYEWALL FORMING OUTBOARD OF THE MOAT. AS THE ERC CONTINUES TO EVOLVE, IT WOULD BE EXPECTED THAT THE EYE WOULD STEADILY ENLARGE AS IT CLEARS OUT, BUT THE MSI TELLS THE OPPOSITE STORY, WITH VHTS REDEVELOPING ALONG THE INNER EYEWALL AND A NEW PINHOLE TYPE EYE TAKING SHAPE. WHETHER THE DRY AIR CAN BE MIXED OUT AND HOW LONG THIS PROCESS TAKES WILL DETERMINE THE FATE OF TY 17W IN THE NEAR-TERM. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE IN THE MSI AND EXTRAPOLATED GMI IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE OVERALL, WITH THE WARM SSTS, HIGH (100 KJ PER CM2) OHC AND STRONG OUTFLOW ALOFT OFFSET BY THE ONGOING ERC AND ASSOCIATED DRY AIR ENTRAINMENT. INITIAL WIND RADII BASIS: SAR DATA CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS RJTD: T5.0 - 90 KTS RCTP: T6.0 - 115 KTS KNES: T6.0 - 115 KTS CIMSS SATCON: 112 KTS AT 222300Z CIMSS ADT: 112 KTS AT 230000Z CIMSS AIDT: 105 KTS AT 230000Z CIMSS D-MINT: 112 KTS AT 222250Z CIMSS D-PRINT: 112 KTS AT 230000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG RADIAL OTHER FACTORS: NORTHWESTWARD OUTFLOW CHANNEL; EYEWALL REPLACEMENT CYCLE (ERC). 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 (TY) 17W (SAUDEL) CONTINUES TO TRACK WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN FLANK OF A EXPANSIVE SUBTROPICAL RIDGE (STR) WHICH EXTENDS FROM SOUTHERN JAPAN TO THE NORTHWEST PACIFIC EAST OF IWO TO. NO SIGNIFICANT CHANGE IN THE TRAJECTORY IS EXPECTED FOR THE NEXT 60 HOURS, AS THE STR REMAINS FIRMLY ENTRENCHED. AROUND TAU 48, THE GLOBAL MODELS AGREE THAT THE RIDGE WILL BEGIN TO REORIENT TO A FLATTER, MORE EAST-WEST ORIENTATION, THOUGH NO SIGNIFICANT CHANGES IN POSITION OR STRENGTH ARE EXPECTED. BEGINNING AROUND TAU 60 HOWEVER, THE GLOBAL MODELS BEGIN TO DIVERGE, THOUGH NOT AS MUCH AS SIX HOURS, ON THE STRENGTH AND IMPACT OF AN UPPER-LEVEL TROUGH MOVING IN FROM THE NORTHWEST. THE GFS CONTINUES TO SHOW A STRONGER, DEEPER TROUGH WHICH INDUCES A BREAK IN THE STR OVER SOUTH KOREA, RESULTING IN A SIGNIFICANT SLOWDOWN AND SLIGHTLY BOWED TRACK FOR TY 17W AS IT MOVES ACROSS THE RYUKYU ISLANDS BEFORE TURNING SOUTHWEST ALONG THE EASTERN FLANK OF A BUILDING STR OVER CHINA AND ULTIMATELY IMPACTING NORTHEASTERN TAIWAN. THE ECMWF ON THE OTHER HAND DEPICTS A MUCH WEAKER TROUGH ALOFT, WHICH HAS MINIMAL IMPACT ON THE STR, LEADING TO A MUCH FASTER, FURTHER SOUTH TRAJECTORY WHICH ALSO ULTIMATELY IMPACTS NORTHEASTERN TAIWAN AFTER TURNING SOUTHWEST ALONG THE EASTERN FLANK OF THE STR OVER CHINA. THE JTWC FORECAST CALLS FOR THE SYSTEM TO SLOW DOWN SIGNIFICANTLY AS IT APPROACHES OKINAWA, REACHING ITS SLOWEST SPEED JUST AFTER PASSING THE RYUKYUS, THEN ACCELERATING SOUTHWESTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, THE ERC SHOULD WRAP UP WITHIN THE NEXT 12 HOURS, AND CONDITIONS WILL REMAIN FAVORABLE FOR ABOUT 24 HOURS AFTER THAT POINT, ALLOWING TY 17W TO REINTENSIFY UP TO A PEAK OF 120 KNOTS. THE ONSET OF INCREASED SHEAR, DECREASING OUTFLOW ALOFT AND DECREASING OHC WILL STEADILY WEAKEN TY 17W AFTER TAU 48 THROUGH THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72, WITH CROSS-TRACK SPREAD INCREASING TO 150NM BETWEEN ECMWF ON THE SOUTHERN EDGE OF THE ENVELOPE AND GFS, GEFS, AND THE AI MODELS ON THE NORTHERN FRINGE. ENSEMBLE GUIDANCE IS ALSO IN GOOD AGREEMENT THROUGH TAU 72, WITH A MEMBER DISPERSION ENVELOPE ROUGHLY ENCOMPASSING THE CENTRAL RYUKYU ISLANDS. THE JTWC FORECAST IS PLACED NEAR THE GFS SOLUTION THROUGH TAU 72, WITH HIGH CONFIDENCE. IN THE LONG-RANGE FORECAST, BOTH THE TRADITIONAL TRACK CONSENSUS AND THE ENSEMBLES SHOW INCREASED UNCERTAINTY. WHILE CROSS-TRACK SPREAD REMAINS CONSISTENT, ALONG-TRACK SPREAD INCREASES SHARPLY AFTER TAU 72, WITH THE ECMWF CONTINUING TO BE THE FASTEST MODEL, THOUGH GFS IS NOW CATCHING UP QUICKLY. BOTH NOW DEPICT LANDFALL BY TAU 120 OVER NORTHEASTERN TAIWAN, WHILE THE CONSENSUS AND JGSM DEPICT LANDFALL IN SOUTHEASTERN CHINA. THE REMAINDER OF THE GUIDANCE, PARTICULARLY THE AI MODELS, LAG FAR BEHIND. ENSEMBLE MEMBER DISPERSION ALSO INCREASES SHARPLY, RESULTING IN INCREASED UNCERTAINTY IN THE LONG-RANGE FORECAST. INTENSITY GUIDANCE HAS SHIFTED SIGNIFICANTLY WEAKER SINCE THE PREVIOUS RUN. THE ONLY MODEL SHOWING ANY INTENSIFICATION NOW IS THE CTCX, WHICH PEAKS OUT AT 120 KNOTS AT TAU 24. THE JTWC FORECAST IS PLACED ON TOP OF THE CTCX TRACKER TO TAU 36, THEN REJOINS THE CLUSTER OF MODELS THROUGH THE REMAINDER OF THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN