WDPN31 PGTW 251500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 010// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.4N 128.2E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 307 NM SOUTH OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) AND PROXY VISIBLE (PROXYVIS) SATELLITE IMAGERY INDICATES THAT TROPICAL STORM (TS) 25W IS UNDERGOING STEADY CONVECTIVE CONSOLIDATION AND MATURATION. DEEP CONVECTION CONTINUES TO PULSE, BUT HAS DEMONSTRATED PERSISTENCE DESPITE MODERATE SOUTHERLY VERTICAL WIND SHEAR (VWS) OVER THE PAST SIX HOURS, CHARACTERIZED BY PERSISTENT OVERSHOOTING TOPS CONCENTRATED NEAR THE INNER CORE. ANIMATED WATER VAPOR IMAGERY AS WELL AS CIMSS AND CIRA ATMOSPHERIC MOTION VECTORS (AMVS) INDICATE A SPLIT IN THE OUTFLOW-LEVEL ENVIRONMENTAL FLOW AROUND THE CORE AND ASSOCIATED VORTEX. THIS CONFIGURATION SUGGESTS SIGNIFICANTLY REDUCED LOCAL VERTICAL SHEAR DIRECTLY OVER THE VORTEX CORE, ALTHOUGH SATELLITE OBSERVATIONS ARE RESTRICTED TO OUTFLOW LEVELS AND NUMERICAL SOUNDINGS CONTINUE TO DEPICT MODERATE, ALBEIT RELAXING, MID-LEVEL SHEAR. A 250853Z WSF-M 37GHZ IMAGE PROVIDED INITIAL CONFIRMATION OF A COMPACT LOW-LEVEL CIRCULATION CENTER (LLCC) EMBEDDED BENEATH DEEP CONVECTION, AND APPROACHING VERTICAL ALIGNMENT. A 251224Z ASCAT-C PASS REVEALED A SMALL BUT WELL-ORGANIZED LLCC WITH STRENGTHENING WINDS AND AN EXPANDING WIND FIELD; HOWEVER, A SLIGHT TILT PERSISTS, WITH CONVECTIVE BURSTING CONFINED PRIMARILY TO THE UPSHEAR-LEFT QUADRANT RELATIVE TO THE SURFACE CIRCULATION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE ASCAT-C DATA. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON A BLEND OF SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW, SUPPORTED BY THE ASCAT PASS. ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH DECREASING SHEAR, HIGH SSTS (29-30C), ELEVATED OCEAN HEAT CONTENT (OHC), AND MODERATE TO STRONG POLEWARD OUTFLOW ALOFT. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF AN EXPANSIVE DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T3.0 - 45 KTS RCTP: T3.0 - 45 KTS CIMSS ADT: 51 KTS AT 251150Z CIMSS AIDT: 44 KTS AT 251150Z CIMSS D-PRINT: 52 KTS AT 251240Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: MODERATE, BUT DECREASING, MID-LEVEL SOUTHEASTERLY SHEAR. 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: TS 25W HAS TRACKED NORTHWESTWARD AT A STEADY 12-13 KNOTS OVER THE PAST SIX HOURS ALONG THE SOUTHWESTERN FLANK OF THE LARGE STR TO THE SOUTH OF JAPAN. OVER THE NEXT 12 HOURS, 25W WILL BEGIN TO DECELERATE AND TURN GRADUALLY NORTHWARD AS IT ENTERS A COL REGION/WEAKNESS IN THE RIDGE. FROM TAU 12 TO TAU 36, 25W WILL GRADUALLY CROSS THE RIDGE AXIS, MAINTAINING A REDUCED TRANSLATION SPEED OF 5-6 KNOTS AS IT PASSES EAST OF MIYAKOJIMA AND THE SOUTHERN RYUKYUS. BY TAU 48, 25W WILL REACH ITS CLOSEST POINT OF APPROACH (CPA) TO OKINAWA AND BEGIN TO ACCELERATE AS THE STR DRIFTS SOUTHWESTWARD AND ELONGATES ALONG A SOUTHWEST-NORTHEAST AXIS. A PASSING MID-LATITUDE TROUGH TO THE NORTH SHOULD EXERT SUFFICIENT FORCING AND EXTEND FAR ENOUGH EQUATORWARD TO CAPTURE 25W AS IT TRACKS PAST THE NORTHERN RYUKYUS, PROMOTING FURTHER ACCELERATION FROM TAU 72 THROUGH THE END OF THE FORECAST. BY TAU 120, 25W WILL BE POSITIONED SOUTH OF TOKYO AND COMMENCE EXTRATROPICAL TRANSITION (ETT). REGARDING INTENSITY: GIVEN IMMINENT VERTICAL AXISYMMETRIZATION AND AN INCREASINGLY FAVORABLE ENVIRONMENT, 25W IS PROJECTED TO MAINTAIN A STEADY INTENSIFICATION RATE WITHIN THE NEXT 12 HOURS. THE FORECAST STOPS JUST SHY OF EXPLICITLY PREDICTING RAPID INTENSIFICATION (RI); HOWEVER, DUE TO ITS COMPACT CORE, 25W MAY OUTPACE CONSENSUS GUIDANCE AND ATTAIN A HIGHER RATE OF INTENSIFICATION THROUGH TAU 48. AFTER PASSING OKINAWA, 25W WILL ENCOUNTER INCREASING ENVIRONMENTAL SHEAR, INITIATING A GRADUAL WEAKENING TREND. THE RATE OF WEAKENING WILL ACCELERATE AFTER TAU 72 AS NORTHWESTERLY SHEAR INCREASES SHARPLY, SSTS COOL, AND 25W BEGINS ETT. TRACK GUIDANCE REMAINS POLARIZED INTO TWO DISTINCT REGIMES. THE ALTERNATIVE SCENARIO REFLECTED IN SELECT DYNAMICAL GUIDANCE (GALWEM, NAVGEM, GFS, HAFS-A, AND CTCX) CONTINUES TO DEPICT RECURVATURE ARRESTED BY A QUASI-STATIONARY MEANDER NEAR OKINAWA WITHIN THE STR COL REGION. GEFS AND MOGREPS PARTIALLY EXHIBIT THIS TENDENCY, WHEREAS THE FULL SUITE OF AI GUIDANCE ALONGSIDE DETERMINISTIC ECMWF CONSISTENTLY DEPICTS A PROGRESSIVE RECURVATURE SCENARIO, WHICH THE JTWC FORECAST CONTINUES TO FAVOR. MODEL DISCUSSION: THE OVERALL ORIENTATION OF TRACK GUIDANCE HAS NOT CHANGED SIGNIFICANTLY, WITH A CONTINUED BIFURCATION AMONG THE MODEL SUITES. THIS REPRESENTS A STRUCTURAL DICHOTOMY BETWEEN THE MAJORITY OF PHYSICS-BASED DYNAMICAL MODELS (EXCLUDING ECMWF) VERSUS THE AI SUITES AUGMENTED BY ECMWF AND ECEPS. WHILE CONSENSUS BETWEEN ECMWF AND AI GUIDANCE BOLSTERS CONFIDENCE IN THE PRIMARY RECURVING SOLUTION, PERSISTENCE IN THE ALTERNATIVE QUASI-STATIONARY SCENARIO WARRANTS MEASURED FORECAST CONFIDENCE, OWING LARGELY TO THE MARGINAL AMPLITUDE AND DYNAMICAL FORCING ASSOCIATED WITH THE APPROACHING MID- LATITUDE SHORTWAVE. IN SUMMARY, NAVGEM STALLS 25W SOUTHWEST OF OKINAWA, WHILE THE HIGH-SPEED OUTLIER WINDBORNE AI TRANSLATES THE SYSTEM NORTHEASTWARD AT OVER 30 KNOTS, PRODUCING AN ALONG-TRACK SPREAD EXCEEDING 1000 NM BY TAU 120. GFS AND ITS CORRESPONDING CLUSTER GENERALLY STALL THE SYSTEM EAST OF OKINAWA. THE REMAINING AI MODELS CLUSTER NEAR THE JTWC FORECAST POSITION AT TAU 120, WHILE ECMWF AND ECEPS LAG APPROXIMATELY 150 NM BEHIND. ENSEMBLES EXHIBIT EXTREME ALONG-TRACK DISPERSION, WITH ENVELOPE EXTENTS RANGING FROM TAIWAN TO HOKKAIDO. THE JTWC FORECAST HEAVILY FAVORS THE AI CONSENSUS MEAN THROUGH THE FORECAST PERIOD, WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE THEREAFTER. INTENSITY GUIDANCE REMAINS DIVERGENT: CTCX AND COTC INDICATE LITTLE TO NO INTENSIFICATION, WHEREAS HAFS-A AND THE RI AIDS (RIDE, RIPA, RI35) PROJECT A PEAK INTENSITY BETWEEN 100-115 KNOTS. THE REMAINDER OF THE GUIDANCE, INCLUDING GOOGLE DEEPMIND, CAPS INTENSITY NEAR 85 KNOTS. THE JTWC FORECAST ALIGNS CLOSELY WITH THE DEEPMIND TRACKER, THOUGH A HIGHER PEAK (NEARING HAFS-A SOLUTIONS) REMAINS DYNAMICALLY PLAUSIBLE SHOULD INNER-CORE VORTEX ALIGNMENT COMPLETE RAPIDLY. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN