WDPN31 PGTW 240900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 18.9N 133.1E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 542 NM SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN ASYMMETRIC SYSTEM EXHIBITING AN IRREGULAR CENTRAL DENSE OVERCAST (CDO) STRUCTURE WITH ENHANCED CONVECTIVE BURSTS CONFINED TO THE NORTHERN PERIPHERY OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 240436Z AMSR3 COLOR-ENHANCED 89GHZ MICROWAVE IMAGE REVEALED A PRONOUNCED ASYMMETRY IN THE LOW-LEVEL STRUCTURE AND SIGNIFICANT VERTICAL TILT OF THE VORTEX CORE, INDICATIVE OF MODERATE MID-LEVEL SOUTHERLY VERTICAL WIND SHEAR (VWS). SYNTHETIC MICROWAVE IMAGERY SUGGESTS THE VORTEX TILT HAS INTENSIFIED, WITH THE MID-LEVEL CIRCULATION DISPLACED APPROXIMATELY 30 NM NORTHWEST OF THE INCREASINGLY DISRUPTED AND PARTIALLY EXPOSED LLCC. EARLIER SCATTEROMETRY DATA DEPICTED A VERY ASYMMETRIC WIND FIELD, WITH GALE- FORCE WINDS RESTRICTED TO THE NORTHERN SEMICIRCLE, WHILE WINDS TO THE SOUTH WERE GENERALLY LESS THAN 20-25 KNOTS. ANIMATED WATER VAPOR IMAGERY AND CIRA ADVECTED LAYER TOTAL PRECIPITABLE WATER (TPW) INDICATE A SUBSTANTIAL MID-LEVEL DRY AIR INTRUSION PERSISTING ACROSS THE SOUTHERN QUADRANT OF THE CIRCULATION. THE SYSTEM IS STRUGGLING TO ESTABLISH AXISYMMETRY DUE TO THE DELETERIOUS COMBINATION OF MODERATE VWS AND MID-LEVEL DRY AIR ENTRAINMENT INTO THE CORE. THE INITIAL POSITION IS ASSESSED WITH MODERATE CONFIDENCE BASED ON AN EXTRAPOLATION OF THE AMSR3 DATA NOTED ABOVE. THE INITIAL INTENSITY IS ASSESSED WITH MODERATE CONFIDENCE, BASED ON A BLEND OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS ARE GENERALLY FAVORABLE, WITH THE NOTABLE EXCEPTIONS DISCUSSED ABOVE. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF HONSHU. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS CIMSS SATCON: 44 KTS AT 240416Z CIMSS ADT: 47 KTS AT 240540Z CIMSS AIDT: 39 KTS AT 240540Z CIMSS D-MINT: 49 KTS AT 240418Z CIMSS D-PRINT: 50 KTS AT 240640Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: VORTEX TILT; MODERATE MID-LEVEL SHEAR; DRY AIR ENTRAINMENT ALONG THE SOUTHERN FLANK. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM (TS) 25W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR FOR THE NEXT 36 HOURS. FORWARD TRANSLATIONAL SPEED IS PROJECTED TO DECELERATE SIGNIFICANTLY AFTER TAU 24 AS THE STR WEAKENS AND SHIFTS SLIGHTLY EASTWARD. THE SYSTEM IS EXPECTED TO APPROACH THE STR AXIS BY TAU 48, DECELERATING FURTHER TO 5-6 KNOTS AS IT MOVE INTO A DEEP-LAYER COL REGION LOCATED BETWEEN THE PRIMARY STR TO THE EAST AND A SECONDARY STR OVER CENTRAL CHINA. THE TAU 48 TO TAU 60 TIMEFRAME REPRESENTS THE CRITICAL FORECAST DECISION POINT, AS TS 25W BECOMES WEAKLY STEERED WITHIN THIS COL REGION AT THE RIDGE AXIS. THE BASELINE FORECAST IS PREDICATED ON A MID-LATITUDE SHORTWAVE TROUGH TRANSITING TO THE NORTH PROVIDING SUFFICIENT FORCING TO EXTRACT TS 25W FROM THE COL REGION, FACILITATING A RECURVATURE ROUTE AROUND THE SUBTROPICAL RIDGE AXIS TOWARD THE NORTHEAST. THIS SCENARIO IS SUPPORTED BY ALL OF THE ARTIFICIAL INTELLIGENCE (AI) MODELS AND TO A LESSER EXTENT BY THE ECMWF AND THE GEFS ENSEMBLE MEAN. HOWEVER, SUBSTANTIAL UNCERTAINTY PERSISTS REGARDING THE TRACK SCENARIO. THE TRANSITING MID-LATITUDE TROUGH EXHIBITS MODEST AMPLITUDE AND LIMITED THERMODYNAMIC SUPPORT, RENDERING AN ALTERNATE TRACK REALIZATION PLAUSIBLE. THE ALTERNATE SCENARIO IS BEST EXEMPLIFIED BY THE GFS, WHICH IS CONSISTENT WITH THE OTHER MODELS THROUGH TAU 48. AFTER TAU 60 HOWEVER THE GFS DEPICTS A RAPID SLOWDOWN IN TRACK SPEED, WITH THE SYSTEM BECOMING NEARLY STATIONARY AFTER TAU 72, TO THE SOUTH OF OKINAWA. THE GFS SHOWS THE SYSTEM REMAINING STUCK IN THE COL-REGION, AS THE TROUGH TO THE NORTH IS TOO WEAK TO PULL IT POLEWARD. THE GFS SHOWS TS 25W REMAINING SOUTH OF OKINAWA THROUGH TAU 120 BEFORE EVENTUALLY TURNING SOUTHWARD BEYOND DAY SIX. IN REGARDS TO INTENSITY, TS 25W WILL STRUGGLE TO INTENSIFY OVER THE NEXT 12 TO 24 HOURS UNDER THE NEGATIVE INFLUENCE OF MODERATE MID-LEVEL SHEAR AND DRY AIR ENTRAINMENT. BY TAU 24, NUMERICAL GUIDANCE INDICATES AN IMPROVING THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY ENHANCED UPPER-LEVEL DIVERGENT OUTFLOW, DECREASING VWS, AND REGIONAL MOISTENING, ENABLING CONDITIONS CONDUCIVE TO A PERIOD OF RAPID INTENSIFICATION (RI) BETWEEN TAU 24 AND TAU 48. THE SYSTEM IS PROJECTED TO REACH ITS PEAK INTENSITY NEAR THE RIDGE AXIS BEFORE COMMENCING A STEADY WEAKENING TREND DRIVEN BY INCREASING SHEAR AND DRY AIR ENTRAINMENT. IN THE ALTERNATE SCENARIO, HOWEVER, THE EXTENDED DWELL TIME IN A FAVORABLE ENVIRONMENT WOULD DELAY THE ONSET OF SHEAR DEGRADATION, POTENTIALLY ALLOWING TS 25W TO ATTAIN A HIGHER PEAK INTENSITY ROUGHLY 24 HOURS LATER THAN PREDICTED IN THE BASELINE OUTLOOK. MODEL DISCUSSION: MODEL GUIDANCE IS HIGHLY UNCERTAIN, WITH A LARGE AMOUNT OF PRIMARILY ALONG-TRACK SPEED, WITH THE UNCERTAINTY FOCUSED BETWEEN THE AI-BASED AND THE PHYSICS-BASED MODELS, AND AFTER TAU 60. UP TO TAU 60, THE MODELS ARE TIGHTLY CONFINED TO A NARROW ENVELOPE, SUPPORTING THE JTWC FORECAST WITH HIGH CONFIDENCE. THE ONLY OUTLIERS DURING THIS TIME ARE THE ECMWF WHICH BEGINS TO PULL THE SYSTEM NORTHWARD AFTER TAU 48 AND LIES SOUTH AND EAST OF ALL THE OTHER MODELS BY TAU 60, AND THE NAVGEM-UKMET COMBO WHICH TRACKS THE SYSTEM STRAIGHT NORTHWESTWARD, OPENING UP SOME DISTANCE TO THE SOUTH AND WEST OF THE ENVELOPE. AT THIS POINT, THINGS DIVERGE RAPIDLY AND SIGNIFICANTLY. THE AI-BASED MODELS START TO OUTRACE THE OTHERS AS EARLY AS TAU 72, INCREASING THE RATE OF ACCELERATION THEREAFTER, RESULTING IN THE MOST AGGRESSIVE OF THEM (EXPERIMENTAL GOOGLE DEEP MIND) BEING POSITIONED OVER 500NM NORTHEAST OF THE CONSENSUS MEAN BY TAU 120. WHILE THE CONSENSUS MEAN IS BEING DRAGGED SLOWER BY THE UNREALISTIC NAVGEM-UKMET COMBO PULLING THE SYSTEM TOWARDS TAIPEI, ALL OF THE PHYSICS-BASED MODEL GUIDANCE SHOWS A MUCH SLOWER PROGRESSION NORTHWARD, WITH THE GFS NEVER RECURVING THE SYSTEM. THE EXPERIMENTAL JTWC SUPER-ENSEMBLE MEAN DEPICTS A SLOW RECURVE SCENARIO, WITH ACCELERATION OCCURRING PRIMARILY BEYOND TAU 120. THE JTWC FORECAST IS PLACED NEAR THE AI CONSENSUS THROUGH TAU 60. THEREAFTER IT IS POSITIONED NEAR THE MID-POINT BETWEEN THE AI AND TRADITIONAL CONSENSUS MEAN POSITIONS, ROUGHLY CONSISTENT WITH THE SUPER-ENSEMBLE MEAN. INTENSITY GUIDANCE IS ALSO MIXED, AND HIGHLY DEPENDENT UPON THE TRACK FORECAST, THEREFORE HIGHLY UNCERTAIN. THE HAFS-A IS VERY AGGRESSIVE, REACHING A PEAK APPROACHING 130 KNOTS BY TAU 72, THOUGH TRACK-WISE, IT IS CONSISTENT WITH THE GFS. THE CTCX AND SHIPS GUIDANCE MEANWHILE IS MUCH LESS AGGRESSIVE, REACHING A MAXIMUM OF JUST 75 KNOTS. MEANWHILE, MULTIPLE RI AIDS HAVE TRIGGERED, SOME REACHING AS HIGH AS 140 KNOTS (COAMPS-TC ENSEMBLE), WHILE MULTIPLE ENSEMBLE-BASED RI PROBABILITY ESTIMATES EXCEED 80 PERCENT BETWEEN TAU 24 AND 48. THE JTWC FORECAST SPECIFICALLY CALLS FOR RI DURING THE 24-48 HOUR POINT, AND MOST CLOSELY TRACKS THE OPERATIONAL GOOGLE DEEPMIND INTENSITY GUIDANCE. HOWEVER, CONFIDENCE IN BOTH THE TRACK AND INTENSITY IS LOW AFTER TAU 72 DUE TO HIGHLY UNCERTAIN NATURE OF THE FORECAST AND POTENTIAL ALTERNATE SCENARIO. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN