WDPN31 PGTW 230900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (CHAMPI) WARNING NR 010 RELOCATED// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.1N 140.5E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 464 NM SOUTH OF IWO TO, JAPAN MOVEMENT PAST 6 HOURS: NORTHWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A COMPACT SYSTEM THAT HAS BEGUN TO CONSOLIDATE AS CONVECTIVE TOPS DEEPENED AND RAIN BANDS HAVE BECOME MORE DEFINED. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A LOW LEVEL CIRCULATION (LLC) FEATURE IN THE 230416Z ATMS MICROWAVE IMAGE AND LINED UP WITH AN LLC IN THE 230207Z SCATTEROMETRY BULLSEYE PASS. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN OVERALL ASSESSMENT OF BELOW AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE IMPROVED STATE OF THE SYSTEM. INITIAL WIND RADII BASIS: SCATTEROMETRY. QUADRANTS SLIGHTLY EXPANDED FROM RECENT PASS TO REFLECT THE STORM INTENSIFICATION. 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: 44 KTS AT 230045Z CIMSS ADT: 47 KTS AT 230540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: WEAK POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH 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 06W WILL TRACK MORE NORTH-NORTHWESTWARD AS IT GETS STEERED AT A HIGHER LAYER OF ALONG THE WESTERN PERIPHERY OF THE STR, THEN AFTER TAU 48, MORE NORTHWARD AS IT CRESTS THE STR AXIS. AFTER TAU 72, THE CYCLONE WILL ACCELERATE NORTH-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. AFTERWARD, INCREASING VWS AND COOLING SSTS WILL SLOWLY ERODE THE CYCLONE. CONCURRENTLY BY TAU 96, 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 300NM AT TAU 72 AND 345NM AT TAU 120. 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 NOTABLE MODEL DIFFERENCES IN ALONG-TRACK ACCELERATION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN