WDPN31 PGTW 231500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (CHAMPI) WARNING NR 011// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 18.2N 140.7E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 397 NM SOUTH OF IWO TO MOVEMENT PAST 6 HOURS: NORTHWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM HAS SLIGHTLY EXPANDED, OTHERWISE, IT MAINTAINED OVERALL CONVECTIVE AND WRAP SIGNATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A LOW LEVEL HOOK FEATURE IN THE 231037Z AMSUB IMAGE. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES, SUPPORTED BY A 231127Z METOP-C ASCATUHR SHOWING 34-50KTS NEAR THE CENTER, AND REFLECTS THE SUSTAINED EIR SIGNATURE. INITIAL WIND RADII BASIS: WITH MINOR ADJUSTMENT ALONG THE NORTHEAST QUADRANT TO REFLECT INCREASED CONVECTIVE ACTIVITY. CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF THE MID-LAYER REFLECTION OF THE STR TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 53 KTS AT 230940Z CIMSS ADT: 57 KTS AT 231140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: WEAK POLEWARD 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: TS 06W WILL CONTINUE TO TRACK GENERALLY NORTHWARD UNDER THE STEERING INFLUENCE OF THE STR UP TO TAU 48 WHEN IT CRESTS THE STR AXIS. AFTERWARD, THE CYCLONE WILL ACCELERATE NORTH-NORTHEASTWARD, THEN NORTHEASTWARD ON THE POLEWARD SIDE OF THE STR AXIS. THE MARGINALLY FAVORABLE ENVIRONMENT, ASSESSED ABOVE, WILL FUEL A GRADUAL INTENSIFICATION TO A PEAK OF 65KTS BY TAU 72 AS POLEWARD OUTFLOW INCREASES DUE TO THE INITIAL EXPOSURE TO THE PREVAILING WESTERLIES. THE PEAK MAY BE HIGHER AND OCCUR NEAR TAU 78. AFTERWARD, INCREASING VWS AND COOLING SSTS WILL SLOWLY ERODE THE CYCLONE. CONCURRENTLY BY TAU 72, IT WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT ENTERS THE COLD BAROCLINIC ZONE AND MERGES WITH THE BAIYU FRONTAL BOUNDARY SOUTHEAST OF JAPAN. BY TAU 120, TS CHAMPI WILL COMPLETE ETT AND EMBED INTO THE GRADIENT FLOW AS A STRONG GALE-FORCE COLD CORE LOW WITH AN EXPANDING WIND FIELD. MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT WITH GRADUAL SPREADING TO 140NM AT TAU 48 AND 300NM AT TAU 96. JGSM IS THE SOLE OUTLIER ON THE LEFT MARGIN OF THE MODEL ENVELOPE. THIS LENDS MEDIUM CONFIDENCE TO THE NEAR- TO MID-TERM PORTION OF THE JTWC TRACK FORECAST THAT IS LAID JUST TO THE RIGHT OF AND SLIGHTLY FASTER THAN THE MODEL CONSENSUS (CONW). ON THE OTHER HAND, THERE IS LOW CONFIDENCE IN THE EXTENDED POTION OF THE FORECAST TO ACCOUNT FOR THE LARGE SPREAD ALONG- AND ACROSS-TRACK IN THE MODELS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72 - 96 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72 - 96 HR: LOW// NNNN