WDPN32 PGTW 151500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (CHAMPI) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 11.0N 157.4E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 750 NM EAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS EXPLOSIVE DEEP CONVECTION PERSISTING ALONG THE WESTERN SIDE OF THE CIRCULATION WITH EXPANDING UPPER-LEVEL OUTFLOW. THE OVERSHOOTING CLOUD TOPS HAVE REACHED TEMPERATURES AS COLD AS -97 DEGREES CELSIUS. THE SYSTEM IS LIKELY STILL TILTED SOUTHWESTWARD WITH HEIGHT AND BATTLING MODERATE NORTHEASTERLY VERTICAL WIND SHEAR (VWS). HOWEVER, THE SYSTEM MAY BE BRIEFLY OVERCOMING THE EFFECTS OF VWS AS GRAVITY WAVES EMANATE RADIALLY FROM THE DEEP CONVECTION. MOST NOTABLY, THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS BECOME EMBEDDED IN THE NASCENT CENTRAL DENSE OVERCAST (CDO), WITH CURVED BANDING BEGINNING TO DEVELOP ALONG THE NORTHERN PERIPHERY. A 151025Z ASCAT-C PASS REVEALED AN ELONGATED LLCC WITH GALE-FORCE WINDS CONFINED TO THE SOUTHERN SEMICIRCLE. BASED ON THESE DATA AND THE IMPROVED CONVECTIVE STRUCTURE, 29W HAS BEEN UPGRADED TO A 35-KT TROPICAL STORM (TS) WITH HIGH CONFIDENCE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE, EXTRAPOLATED FROM THE SCATTEROMETER DATA AND HEDGED TOWARD THE NORTHEAST SIDE OF THE RAGGED CDO. THE ENVIRONMENT IS GENERALLY FAVORABLE FOR ADDITIONAL INTENSIFICATION, CHARACTERIZED BY VERY WARM SEA SURFACE TEMPERATURES (SST) OF 29-30 DEGREES CELSIUS, MODERATE UPPER-LEVEL DIVERGENCE FOCUSED ALONG THE WESTERN PERIPHERY, AND PLENTIFUL DEEP-LAYER MOISTURE. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: SOUTHERN FLANK OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) CENTERED NEAR 30N 160E AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.5 - 35 KTS CIMSS ADT: 41 KTS AT 151140Z CIMSS AIDT: 35 KTS AT 151140Z CIMSS D-MINT: 38 KTS AT 151148Z CIMSS D-PRINT: 40 KTS AT 151240Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 15-20 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE INTENSITY FORECAST HAS BEEN ADJUSTED UPWARD BY 5-10 KTS FROM TAU 12 TO TAU 72. FORECAST DISCUSSION: TS 29W IS MOVING WEST TO WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR. THIS RIDGE WILL ERODE FROM TAU 24 TO TAU 48 AS A TROUGH PASSES WELL TO THE NORTH. MEANWHILE, A SHARP MID-LEVEL TROUGH APPROACHING THE KOREAN PENINSULA WILL SUPPORT THE DEVELOPMENT OF A NEW STR OVER HONSHU. THIS RIDGE WILL SETTLE EAST OF HONSHU NEAR TAU 72 AND BECOME THE PRIMARY STEERING MECHANISM FOR TS 29W, MAINTAINING A WEST-NORTHWESTWARD TRAJECTORY THROUGH TAU 120. THE RECENT EXPLOSIVE CONVECTION AND ONGOING VORTEX CONSOLIDATION MAY FORESHADOW SIGNIFICANT INTENSIFICATION ONCE AXISYMMETRIZATION IS ACHIEVED. VWS WILL EASE TOWARD TAU 60, WHILE TS 29W TRAVERSES VERY WARM SST OF 29-30 DEGREES CELSIUS. THE FORECAST CALLS FOR THE SYSTEM TO BECOME SUFFICIENTLY ORGANIZED TO BEGIN RAPID INTENSIFICATION (RI) NEAR TAU 36, REACHING TYPHOON STRENGTH SHORTLY THEREAFTER AND PEAKING AT 125 KTS AT TAU 96. ALTHOUGH THE ENVIRONMENT BECOMES EVEN MORE FAVORABLE AFTER TAU 72, CHARACTERIZED BY WARMER SST, HIGHER OHC, AND 5-10 KTS OF VWS, THE FORECAST CONSERVATIVELY LEVELS OFF THE INTENSITY AFTER TAU 96 TO ACCOUNT FOR DIFFICULT-TO-PREDICT FLUCTUATIONS IN INTENSITY CAUSED BY INTERNAL TROPICAL CYCLONE DYNAMICS. MODEL DISCUSSION: THE OVERALL TRACK GUIDANCE REMAINS TIGHT BUT HAS SHIFTED SOUTHWARD ONCE AGAIN. THE BULK OF THE DYNAMICAL AIDS LIES ON THE POLEWARD SIDE OF THE GUIDANCE ENVELOPE, WHILE THE AI MODELS LEAN TOWARD A MORE WESTWARD TRAJECTORY. GOOGLE DEEPMIND HAS ALSO SHIFTED SOUTHWARD AND NOW TAKES THE SYSTEM 30 NM SOUTH OF GUAM. THE MULTI-MODEL CONSENSUS (CONW) AND ECMWF ARE AIMED AT CENTRAL TO NORTHERN GUAM, WHILE GFS AND NAVGEM TARGET THE CHANNEL BETWEEN ROTA AND GUAM. THE AI-MODEL MEAN CLIPS THE SOUTHERN TIP OF GUAM. NEARLY ALL MODELS TRACK THE SYSTEM SOUTH OF ROTA, WITH THE CROSS-TRACK SPREAD AMONG THE RELIABLE AIDS NEAR THE CPA TO GUAM MEASURING 70 NM. THE JTWC FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS FORECAST, POSITIONED BETWEEN CONW AND THE AI-MODEL MEAN BUT HEDGED CLOSER TO THE AI-MODEL MEAN. IF CURRENT TRENDS CONTINUE, SUBSEQUENT FORECASTS MAY NEED TO SHIFT THE TRACK FARTHER SOUTH. THE INTENSITY AIDS HAVE TRENDED STRONGER THIS CYCLE. DEEPMIND NOW DEPICTS VERY AGGRESSIVE INTENSIFICATION, BRINGING TS 29W TO 115-130 KTS BY TAU 60. HAFS-A AND GFS ARE SLOWER TO INTENSIFY THE SYSTEM FOR THE FIRST 60 HOURS. HOWEVER, HAFS-A EVENTUALLY STRENGTHENS TS 29W TO 155 KTS AT THE END OF THE FORECAST PERIOD. THE COAMPS-TC AND DEEPMIND ENSEMBLES PEG THE RI PROBABILITY NEAR 80 PERCENT, WITH 75-85 PERCENT OF THE MEMBERS ACHIEVING SUPER TYPHOON INTENSITY BY TAU 96. THE JTWC INTENSITY FORECAST HAS BEEN INCREASED BY 5-10 KTS FROM TAU 12 THROUGH TAU 72, WHILE THE TAU 96 AND TAU 120 FORECAST INTENSITIES REMAIN UNCHANGED. THE FORECAST LIES NEAR THE CENTER OF THE GUIDANCE ENVELOPE THROUGH TAU 48, THEN TRENDS TOWARD THE UPPER END OF THE ENVELOPE BY TAU 96 AND TAU 120. IF TS 29W CONTINUES TO CONSOLIDATE AT THE CURRENT RATE, SUBSEQUENT INTENSITY FORECASTS MAY NEED TO BE FURTHER INCREASED. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN