WDPN31 PGTW 241500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (CHAMPI) WARNING NR 015// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.8N 139.7E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 313 NM SOUTH-SOUTHWEST OF IWO TO MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM IS STEADILY IMPROVING IN OVERALL STRUCTURE, THOUGH STILL STRUGGLING SOMEWHAT WITHIN A RELATIVELY WEAK OUTFLOW ENVIRONMENT. BASED ON A SERIES OF SSMIS 89 GHZ MICROWAVE IMAGES BETWEEN 0630Z - 0934Z, DEEP CONVECTION HAS CONTINUED TO DEVELOP AND BY THE 0934Z PASS, HAS COMPLETELY SURROUNDED THE LOW LEVEL CIRCULATION CENTER (LLCC), AND THE 37 GHZ IMAGE CONFIRMS THE PRESENCE OF A DISTINCT MICROWAVE EYE FEATURE. A 241137Z ASCAT-B BULLSEYE PASS LENT HIGH CONFIDENCE TO THE INITIAL POSITION, INTENSITY AND WIND RADII AND PROVIDED GOOD SUPPORT TO AGENCY AND SUBJECTIVE DVORAK INTENSITY ESTIMATES. THE OVERALL ENVIRONMENT IS STEADILY IMPROVING, WITH A POLEWARD OUTFLOW MECHANISM BEGINNING TO DEVELOP, ADDING TO THE ALREADY MODERATE TO STRONG EQUATORWARD OUTFLOW. LOW-LEVEL WATER VAPOR IMAGERY AND HWRF MODEL CROSS-SECTIONS REVEAL THE AIRMASS TO THE WEST HAS MOISTENED OVER THE PREVIOUS 12 HOURS, WHICH IS ALLOWING FOR CONTINUED CONSOLIDATION OF THE CORE, AS CONFIRMED IN THE RECENT MICROWAVE IMAGERY. WITH THE CONTINUED IMPROVEMENT IN THE UPPER-LEVEL PATTERN, THE STAGE IS SET FOR A PERIOD OF MARKED INTENSIFICATION. INITIAL WIND RADII BASIS: SCATTEROMETER DATA. CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T3.0 - 45 KTS RCTP: T2.5 - 35 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 46 KTS AT 241134Z CIMSS ADT: 41 KTS AT 241140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: WEAK POLEWARD OUTFLOW CHANNEL DEVELOPING. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 06W IS FORECAST TO CONTINUE TRACKING NORTH-NORTHWESTWARD THROUGH TAU 24, THEN TURN NORTHWARD BY TAU 36 AS IT APPROACHES THE STR AXIS. BY TAU 48, THE SYSTEM IS EXPECTED TO HAVE ROUNDED THE RIDGE AND BEGIN ACCELERATING NORTHEASTWARD. BY AROUND TAU 60, TS 06W WILL BEGIN TO UNDERGO EXTRATROPICAL TRANSITION (ETT) AS IT MOVES OVER RAPIDLY COOLING WATERS NORTH OF THE 28TH LATITUDE AND BEGINS TO INTERACT WITH THE BAIU BOUNDARY. THE SYSTEM IS EXPECTED TO COMPLETE ETT NO LATER THAN TAU 96, BUT LIKELY AS EARLY AS TAU 84, TO THE EAST OF NORTHERN HONSHU, AS IT BECOMES EMBEDDED UNDER THE STRONG MID-LATITUDE WESTERLY FLOW ALOFT. WITH THE ENVIRONMENTAL CONDITIONS SHOWING SIGNS OF STEADY IMPROVEMENT, THE DEVELOPMENT OF DUAL CHANNEL OUTFLOW IN THE NEAR-TERM, WARM SSTS (29-30 C) AND LOW VWS, THE JTWC INTENSITY FORECAST CALLS FOR STEADY INTENSIFICATION TO A PEAK OF 75 KTS BETWEEN TAU 36 AND TAU 48. AFTER TAU 48, THE SYSTEM WILL CROSS OVER MUCH COOLER WATERS (LESS THAN 26C), AND ENCOUNTER DRAMATICALLY INCREASING VWS, WHICH WILL SERVE TO OFFSET THE ROBUST POLEWARD OUTFLOW ASSOCIATED WITH THE DIVERGENT 200MB FLOW, AND INDUCE RAPID DECAY OF THE SYSTEM AS IT RACES NORTHEAST AND COMPLETES ETT. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN OVERALL GOOD AGREEMENT ON THE OVERALL SCENARIO, BUT IS BEGINNING TO SHOW INCREASING SPREAD WITHIN THE CONSENSUS MEMBERS IN THE EARLY PORTIONS OF THE FORECAST. TAU 48 SPREAD HAS INCREASED TO 105 NM, WHILE SPREAD AT TAU 96 HAS DECREASED TO 210 NM. ALONG TRACK UNCERTAINTY COMPRISES THE MAJORITY OF THE SPREAD AT TAU 96, AS WOULD BE EXPECTED WITH THE RECURVING SYSTEM UNDERGOING ETT. THE JTWC FORECAST LIES SLIGHTLY RIGHT OF THE MULTI-MODEL CONSENSUS MEAN THROUGH THE DURATION OF THE FORECAST, WITH ONLY THE GFS AND NAVGEM DETERMINISTIC SOLUTIONS BEING FURTHER RIGHT. THE JTWC INTENSITY FORECAST IS SLIGHTLY LOWER THAN THE MULTI-MODEL CONSENSUS THROUGH TAU 72, WITH A FAIRLY LARGE SPREAD IN POTENTIAL PEAK INTENSITY, AS DENOTED BY THE HWRF SOLUTION INDICATING A PEAK OF 95 KTS. BASED ON THE OVERALL ENVIRONMENT, THERE REMAINS THE POSSIBILITY OF A HIGHER PEAK INTENSITY, HOWEVER THE SYSTEM HAS ONLY LIMITED TIME BEFORE THE IMPACT OF SIGNIFICANT SHEAR AND DECREASING SSTS EMPLACE A CAP ON THE PEAK INTENSITY. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN