WDPN31 PGTW 041500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 035// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 25.2N 140.6E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 695 NM EAST OF KADENA AB MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 50 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TYPHOON (TY) 12W (DOLPHIN) CONTINUES TO OUTPERFORM EXPECTATIONS, MAINTAINING A COMPACT INNER CORE OF DEEP CONVECTION AND A SYMMETRIC BUT THIN EYEWALL AND A 17NM WIDE EYE FEATURE. THE EYE IS SUFFICIENTLY CLOUD-FREE TO MAINTAIN A 17C EYE TEMPERATURE WHILE MULTIPLE MESOVORTICES ARE VISIBLE, EVEN IN THE SHORTWAVE INFRARED (SWIR) LOOP. RELATIVELY DRY MID-LEVEL AIR IS CLEARLY ENTRAINED ALONG THE EASTERN SIDE OF THE CIRCULATION, NOW WRAPPING AROUND TO THE WESTERN FLANK, PRODUCING A CLEAR MOAT FEATURE. THESE FEATURES WERE BECOMING EVIDENT IN A 040748Z WSF-M 89GHZ MICROWAVE IMAGE, ALONG WITH A THINNING AND EROSION OF THE NORTHWESTERN EYEWALL, LIKELY DUE TO ELEVATED NORTHWESTERLY UPPER-LEVEL SHEAR AND SOME DRY MID-LEVEL AIR IN THAT QUADRANT. A 040842Z RCM-3 SAR PASS REVEALED A VMAX (PEAK) OF 115 KNOTS, AND A VMAX (MEAN) OF 106 KNOTS, SUPPORTING THE 0600Z INTENSITY ESTIMATE OF 115 KNOTS WITH HIGH CONFIDENCE. THE SAR ALSO DEPICTED A PATCH OF LIGHTER (40-50 KNOTS) WINDS IN THE SOUTHEASTERN QUADRANT, WHICH IS BACKED UP BY THE SAME FEATURE IN THE 041152Z ASCAT-B PASS. BOTH SENSORS ALSO INDICATED THE CONTINUED EXPANSION OF THE ALREADY VERY LARGE WIND FIELD. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 17NM WIDE EYE IN THE EIR. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN EXTRAPOLATION OF THE EARLIER SAR DATA, SUPPORTED BY AN AVERAGING OF THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES AND THE CIMSS ADT AND AIDT-V2 ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS REMAIN OVERALL FAVORABLE, CHARACTERIZED BY STRONG RADIAL OUTFLOW ALOFT AND LOW DEEP-LAYER SHEAR. WHILE SSTS IN THE REGION ARE THE HIGHEST OF ANYWHERE IN THE WESTERN NORTH PACIFIC, THE WARM LAYER IS THIN, WITH LOW OHC AND THE EXPANSIVE WIND FIELD IS INDUCING OCEANIC UPWELLING ACROSS A VAST EXPANSE. THIS IS LEADING TO AN OVERALL REDUCTION IN SSTS NEAR THE CORE OF THE SYSTEM AND CERTAINLY IN THE EASTERN AND NORTHERN PORTIONS, MARGINALLY OFFSETTING THE OTHERWISE FAVORABLE CONDITIONS. ADDITIONALLY, MODEL-BASED SOUNDINGS SUGGEST A LAYER OF ENHANCED (10-15 KTS) NORTHWESTERLY SHEAR IN THE MID- TO UPPER-LEVELS. INITIAL WIND RADII BASIS: SCATTEROMETER AND SAR DATA. CURRENT STEERING MECHANISM: SOUTHEASTERN FLANK OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED OVER THE NORTH-CENTRAL SEA OF JAPAN (SOJ). AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS RJTD: T6.0 - 115 KTS RCTP: T5.5 - 102 KTS KNES: T5.5 - 102 KTS CIMSS ADT: 109 KTS AT 041230Z CIMSS AIDT: 110 KTS AT 041230Z CIMSS D-PRINT: 91 KTS AT 041230Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG RADIAL OTHER FACTORS: MODERATE EASTWARD OUTFLOW CHANNEL ALONG 33N LATITUDE, AT THE BASE OF AN UPPER-LEVEL TROUGH TO THE NORTHEAST; UPWELLING OF COOLER SUBSURFACE WATERS. 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: TY 12W CONTINUES TO EXHIBIT OCCASIONAL TROCHOIDAL MOTION, PARTICULARLY AFTER IT PASSED OVER NORTH IWO TO ISLAND, BRIEFLY TRACKING WEST-SOUTHWESTWARD BEFORE RECENTLY RESUMING A MORE WEST- NORTHWESTWARD TRACK. THE TRACK MADE GOOD OVER THE PAST SIX HOURS HAS BEEN JUST SOUTH OF DUE WEST, AT 12 KNOTS, MOVING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYER STR WHICH IS CENTERED ANOMALOUSLY NORTH IN THE SEA OF JAPAN. EVEN THOUGH EVEN THOUGH TROCHOIDAL OSCILLATIONS ARE EXPECTED TO CONTINUE, THE OVERALL TRACK WILL REMAIN WEST-NORTHWESTWARD AT A FAIRLY STEADY 10-12 KNOTS THROUGH TAU 48, WITH THE SYSTEM PASSING VERY CLOSE TO MINAMI DAITO JIMA BY THIS POINT IN THE FORECAST. BY TAU 48, A DEEP UPPER-LEVEL TROUGH WILL MOVE INTO NORTHEASTERN MANCHURIA. THE TROUGH WILL CONTINUE MOVING EASTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD. WHILE IT DOES NOT EXTEND SOUTH BEYOND THE KOREAN PENINSULA, THE TROUGH WILL ERODE THE STR FROM THE WEST AND ALLOW FOR DEVELOPMENT OF A WEAKNESS IN THE RIDGE TO DEVELOP OVER KOREA. THIS WILL WEAKEN THE STEERING GRADIENT, ALLOWING TY 12W TO SLOW AS IT APPROACHES THE RYUKYU ISLANDS. TRACK SPEEDS SLOW TO JUST 4-5 KNOTS AFTER THE SYSTEM MOVES INTO THE EAST CHINA SEA. BY THE END OF THE FORECAST PERIOD, THE SYSTEM WILL BEGIN A GRADUAL TURN TOWARDS THE NORTHWEST AS IT BEGINS TO BE STEERED BY A BUILDING RIDGE OVER SOUTHERN JAPAN. TY 12W IS FORECAST TO MAKE LANDFALL ON OKINAWA NEAR TAU 72 BEFORE MOVING INTO THE EAST CHINA SEA. REGARDING INTENSITY, THE SYSTEM APPEARS TO HAVE REACHED A STEADY STATE, ACHIEVING BALANCE BETWEEN COMPETING ENVIRONMENTAL FACTORS. THE FORECAST CALLS FOR THE SYSTEM TO WEAKEN SLIGHTLY OVER THE NEXT 12 HOURS AND THEN MAINTAIN INTENSITY THROUGH TAU 36 BEFORE EMBARKING ON A STEPWISE WEAKENING TREND THROUGH LANDFALL AT OKINAWA DUE PRIMARILY TO MARGINALLY LOWER SSTS FROM OCEANIC UPWELLING AS WELL AS A REDUCTION IN OUTFLOW ALOFT. AFTER TAU 72, THE SYSTEM WILL WEAKEN MORE RAPIDLY AS IT SLOWS DOWN AND UPWELLING BECOMES MORE SIGNIFICANT. WHILE THE INTENSITY IS FORECAST TO STEADILY DECREASE, THE WIND FIELD CONVERSELY IS EXPECTED TO CONTINUE ITS EXPANSION, WITH GALE- FORCE WINDS EXPECTED TO COVER AN ALMOST 600NM DIAMETER SWATH OF THE EAST CHINA SEA BY TAU 120. MODEL DISCUSSION: TRACK GUIDANCE IS IN STRONG AGREEMENT THROUGH TAU 48, WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD. BEYOND THIS POINT HOWEVER, THE CONSENSUS MEMBERS BEGIN TO DIVERGE CONSIDERABLY. THE GFS, JGSM AND NAVGEM CONTINUE TO BE THE PRIMARY OUTLIERS, FIRST DIPPING THE SYSTEM SOUTH OF OKINAWA AS EARLY AS TAU 60, BEFORE TURNING SHARPLY NORTHWARD DIRECTLY ON TOP OF OKINAWA AND ENDING UP NORTH OF OKINAWA BY TAU 120. WITH THIS MODEL RUN, THE ECMWF AND GEFS MEAN ALSO DIVERGE FROM THE PACK, AFTER TAU 72 WHERE THE RUN THE SYSTEM SOUTHWESTWARD TO NEAR THE COAST OF CHINA BY TAU 120. THE REMAINDER OF THE CONSENSUS, INCLUDING THE CONSENSUS MEAN, AND THE AI MODELS CONTINUE TO BE CONSTRAINED TO A TIGHTLY DEFINED ENVELOPE WHICH SHOWS A WEST-NORTHWESTWARD, DECELERATING TRACK, FROM TAU 72 TO TAU 120. THE JTWC FORECAST IS PLACED NEAR THE AI CONSENSUS MEAN THROUGH THE FORECAST PERIOD. INTENSITY GUIDANCE IS MIXED, WITH A FAIRLY WIDE RANGE IN FORECASTED INTENSITIES; THE CTCX MODEL CONTINUES TO SUPPORT INTENSIFICATION, UP TO 135 KNOTS BY TAU 36, WHILE THE HAFS-A DEPICTS A RAPID WEAKENING TO JUST 75 KNOTS BY TAU 48 FOLLOWED BY RAPID INTENSIFICATION UP TO A PEAK NEAR 100 KNOTS JUST PRIOR TO LANDFALL ON OKINAWA. THE HWRF, EXPERIMENTAL GOOGLE DEEPMIND (GDM) AND CONSENSUS MEAN DEPICT A MORE LIKELY SCENARIO OF A GENERALLY FLAT OR SLIGHT WEAKENING TREND THROUGH TAU 72 FOLLOWED BY MORE RAPID WEAKENING THEREAFTER. THE JTWC FORECAST IS PLACED NEAR THE HAFS-A AND GDM TRACKERS WITH MEDIUM TO LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN