WDPN31 PGTW 250900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.7N 129.3E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 358 NM SOUTH-SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN ASYMMETRIC LOW-LEVEL CIRCULATION CENTER (LLCC), WITH VIGOROUS CONVECTION DEVELOPING NEAR THE CENTER OF A ROUGHLY CIRCULAR CENTRAL DENSE OVERCAST (CDO) FEATURE. A RECENT 250444Z ATMS 89GHZ MICROWAVE PASS RESOLVED STRUCTURAL DETAILS OF THE VORTEX BENEATH THE CDO CANOPY. THERE APPEARS TO BE A RELATIVELY STRONG MID-LEVEL VORTEX ASSOCIATED WITH THE DEEP CONVECTION AND OVERSHOOTING TOPS, WHILE THE SURFACE LLCC REMAINS TILTED TO THE SOUTHEAST, ALTHOUGH VERTICAL DECOUPLING HAS DIMINISHED COMPARED TO 24 HOURS AGO. GFS AND ECMWF MODEL-DERIVED SOUNDINGS AND ENVIRONMENTAL PROFILES SUGGEST RELATIVELY LIGHT DEEP- LAYER SHEAR, WITH MODERATE MID-LEVEL SHEAR TEMPORARILY RETARDING VERTICAL ALIGNMENT. ANIMATED WATER VAPOR IMAGERY DEPICTS A BOW-SHAPED BAND OF UPPER-LEVEL OUTFLOW EXPANDING EASTWARD FROM THE CENTER OF 25W, SUGGESTING THAT AT THE MID- AND UPPER-LEVELS, SHEAR IS RELAXING IN THE VICINITY OF THE CORE AND ENVIRONMENTAL VENTILATION IS DIMINISHING, FAVORING PROGRESSIVE SYSTEM ORGANIZATION. THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE DUE TO THE LACK OF RECENT HIGH-RESOLUTION MICROWAVE IMAGERY AND THE OBSCURED LLCC. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF THE OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH THE PRIMARY INHIBITING FACTOR BEING THE TILTED NATURE OF THE VORTEX. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T2.5 - 35 KTS RCTP: T3.0 - 45 KTS CIMSS SATCON: 44 KTS AT 250640Z CIMSS ADT: 47 KTS AT 250540Z CIMSS AIDT: 41 KTS AT 250540Z CIMSS D-MINT: 40 KTS AT 250444Z CIMSS D-PRINT: 45 KTS AT 250540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: HIGH MID-LEVEL SOUTHERLY SHEAR; DRY AIR WRAPPING INTO THE CORE ALONG THE SOUTHEASTERLY FLANK. ANALYSIS CONFIDENCE: INITIAL POSITION: LOW 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: TS 25W CONTINUES TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN FLANK OF THE LARGE STR POSITIONED TO THE NORTHEAST. TRANSLATION SPEED WILL DECREASE OVER THE NEXT 12 HOURS AS THE SYSTEM APPROACHES THE AXIS OF THE RIDGE AND THE ASSOCIATED COL REGION BETWEEN THE STR TO THE EAST AND A SECONDARY STR OVER CENTRAL CHINA. BETWEEN TAUS 24 AND 48, THE SYSTEM WILL SLOWLY ROUND THE RIDGE AXIS AND GRADUALLY TURN NORTHEASTWARD TO THE EAST OF THE SOUTHERN RYUKYU ISLANDS. BEYOND TAU 48, THE STR TO THE EAST PROGRESSES RAPIDLY NORTHEASTWARD WHILE ELONGATING ALONG A SOUTHWEST-TO-NORTHEAST AXIS. SIMULTANEOUSLY, A MID-LATITUDE SHORTWAVE TROUGH PASSES OVER JAPAN, AND THIS SYNOPTIC EVOLUTION WILL ALLOW TS 25W TO ACCELERATE NORTHEASTWARD, ROUGHLY PARALLELING THE NORTHERN RYUKYUS AND THE JAPANESE MAIN ISLANDS FROM TAU 48 ONWARDS. REGARDING INTENSITY, 25W REMAINS TEMPORARILY CONSTRAINED BY MODERATE TO STRONG MID-LEVEL SHEAR AND DRY MID-LEVEL AIR ENTRAINMENT. MODEL FIELDS, HOWEVER, SUGGEST THAT DRY AIR WILL DILUTE/MIX OUT AND SHEAR WILL CONTINUE TO DECREASE OVER THE NEXT 12 TO 18 HOURS, ALLOWING THE VORTEX TO VERTICALLY ALIGN AND BECOME SYMMETRIC. ONCE THIS OCCURS, 25W WILL INTENSIFY RAPIDLY AS IT ROUNDS THE RIDGE AXIS. PEAK INTENSITY IS EXPECTED AROUND TAU 36 AND WILL PERSIST THROUGH TAU 60, AS COMPETING DYNAMICAL FORCING (INCREASING SHEAR COUNTERBALANCED BY ROBUST POLEWARD OUTFLOW) GOVERNS THE CORE REGION. NORTHWESTERLY SHEAR WILL RAPIDLY INCREASE AFTER TAU 72, USHERING IN SIGNIFICANT DRY AIR AND CONVERGENT FLOW ALOFT, RESULTING IN RAPID WEAKENING THROUGH THE REMAINDER OF THE FORECAST PERIOD. THERE REMAINS CONSIDERABLE UNCERTAINTY IN THE FORECAST, THOUGH AVAILABLE MODEL GUIDANCE IS STARTING TO CONVERGE TOWARD GREATER CONSENSUS. GUIDANCE REMAINS BIFURCATED INTO TWO SCENARIOS; THE SECONDARY SCENARIO IS CONFINED TO SELECT DYNAMICAL GUIDANCE (GFS, UKMET, HAFS-A, COAMPS-TC, AND NAVGEM), WHICH DEPICTS 25W BECOMING QUASI-STATIONARY IN THE VICINITY OF OKINAWA AROUND TAU 72-96 PRIOR TO TURNING EQUATORWARD. THE FACT THAT THE ECMWF, ECMWF ENSEMBLE (ECEPS), AND GFS ENSEMBLE (GEFS) HAVE SHIFTED TO THE PRIMARY RECURVATURE SCENARIO LENDS INCREASED CONFIDENCE IN THAT SOLUTION, THOUGH THE QUASI-STATIONARY OUTCOME CANNOT BE EXCLUDED. INTENSITY IS TIGHTLY COUPLED TO TRACK; A STALLED SYSTEM WOULD REMAIN OVER FAVORABLE SSTS AND LOW SHEAR LONGER, REACHING A HIGHER PEAK INTENSITY APPROXIMATELY 24 HOURS LATER THAN CURRENTLY FORECAST. MODEL DISCUSSION: TRACK GUIDANCE IS STEADILY CONVERGING WITH EACH SUCCESSIVE CYCLE. THE ECMWF, ECEPS, GEFS, AND GALWEM NOW ALIGN WITH ARTIFICIAL INTELLIGENCE/MACHINE LEARNING (AI/ML) CONSENSUS IN DEPICTING A RECURVING TRACK. FURTHERMORE, THE DETERMINISTIC ECMWF OUTPACES BOTH THE AI CONSENSUS AND EC-AIFS TRACKERS FROM TAU 96 ONWARDS. WHILE GFS REMAINS IN THE SLOW/STALLED CLUSTER, IT HAS TRENDED PROGRESSIVELY FARTHER NORTHEASTWARD BEFORE STALLING WITH EACH RECENT CYCLE. THESE SHIFTS PROVIDE INCREASED CONFIDENCE IN THE JTWC FORECAST TRACK. HOWEVER, ALONG-TRACK SPREAD REMAINS SIGNIFICANT, REACHING 900 NM BETWEEN THE NAVGEM SOUTHWEST OF OKINAWA AND THE DEEPMIND AND WINDBORNE AI SOLUTIONS SOUTHEAST OF TOKYO BY TAU 120. THE AI CONSENSUS STRONGLY COINCIDES WITH EC-AIFS AND DETERMINISTIC ECMWF GUIDANCE, AND THE JTWC FORECAST HEAVILY FAVORS THIS CLUSTER THROUGH THE PERIOD. CONFIDENCE IS MEDIUM THROUGH TAU 72 AND LOW THEREAFTER; PERSISTENCE OF THESE TRENDS MAY WARRANT UPGRADING LONG- RANGE CONFIDENCE TO MEDIUM IN SUBSEQUENT BULLETINS. INTENSITY GUIDANCE HAS ALSO NARROWED SPREAD OVER THE PAST 24 HOURS, WITH PEAK PROJECTIONS CONFINED LARGELY TO 80-105 KNOTS. HAFS-A AND CTCX REMAIN THE MOST AGGRESSIVE SOLUTIONS AND DELAY THE PEAK BY APPROXIMATELY 24 HOURS. THE JTWC INTENSITY FORECAST ALIGNS CLOSELY WITH GOOGLE DEEPMIND GUIDANCE THROUGH TAU 60, REMAINING 10-15 KNOTS HIGHER THEREAFTER. CONFIDENCE IS MEDIUM THROUGH TAU 72 AND LOW THEREAFTER. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN