WDPN31 PGTW 230300 COR MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (CHAMPI) WARNING NR 009A CORRECTED// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.0N 140.1E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 279 NM WEST-NORTHWEST OF NAVSTA GUAM MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 11 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES A CENTRAL COLD COVER (CCC) HAS COMPLETELY OBSCURED THE LOW-LEVEL CENTER (LLC) UNDER A MASS OF CONVECTION. A 222055Z SSMIS 91GHZ MICROWAVE IMAGE SHOWS NO ORGANIZED STRUCTURE TO THE MID-LEVEL VORTEX REMAINS SLIGHTLY DISPLACED FROM THE LLC WITH A SW TO NE TILT. THE EMBEDDED LLC UNDER THE CCC IS INDICATIVE OF SLOW GROWTH FOR THE SYSTEM. THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE WITH DRIER AIR TO THE WEST, ALONG WITH WEAK RADIAL OUTFLOW ALOFT. THE CONVECTIVE STRUCTURE HAS IMPROVED SLIGHTLY OVER THE NORTHWEST AND NORTHEAST SECTOR OF THE LLC AS SEEN ON THE LATEST MSI. HOWEVER, THE DRY AIR TO THE WEST WILL CONTINUE TO ALLOW ONLY SLOW DEVELOPMENT. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 42 KTS AT 222128Z CIMSS ADT: 41 KTS AT 222340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: WEAK RADIAL OTHER FACTORS: DRY LOW TO MID-LEVEL AIR MASS TO THE WEST AND SOUTH ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: LOW INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 06W CONTINUES TO TRACK NORTHWESTWARD AROUND THE PERIPHERY OF THE SUBTROPICAL RIDGE TO THE NORTHEAST. A TURN TOWARD THE NORTH BY 48 HOURS AND THEN NORTHEAST BY 72 HOURS AND MODERATE ACCELERATION IS EXPECTED AS THE CYCLONE ROUNDS THE RIDGE NEAR THE BAIU FRONTAL BOUNDARY SOUTHEAST OF JAPAN. THE JTWC INTENSITY FORECAST ASSUMES THAT THE VORTEX WILL BE ABLE TO MIX OUT THE DRY AIR IN A LOW SHEAR ENVIRONMENT DURING THE NEXT 36-48 HOURS, AS SUGGESTED BY THE HWRF AND GFS MODELS, ALLOWING MODEST INTENSIFICATION DURING THE 36-72 HOUR PERIOD TO A PEAK OF AROUND 60 KT. MODERATE NORTHERLY SHEAR AFTER 36 HOURS IS EXPECTED TO BE A LIMITING FACTOR, ESPECIALLY GIVEN THE CYCLONE'S SMALL SIZE, WHICH MAKES IT MORE SUSCEPTIBLE TO SHEAR. THE TIMING ULTIMATELY WILL BE THE HARDEST TO ASCERTAIN WITH ANY CLARITY UNTIL THE SYSTEM IS INFLUENCED BY THE BOUNDARY. THE CYCLONE'S FORWARD SPEED WILL VARY LARGELY IN PART DUE TO THE SENSITIVITY OF TIMING AND POSITION OF THE DEEP-LAYER STEERING FLOW BETWEEN THE SUBTROPICAL RIDGE AND THE BAIU FRONT. THE INTENSITY FORECAST ALSO DEPENDS ON THIS EVOLUTION. EVENTUAL ABSORPTION INTO THE BAIU BOUNDARY REMAINS MOST PLAUSIBLE ALONG WITH THE ASSOCIATED TRANSITION DUE TO COOLER SEA SURFACE TEMPERATURES (SSTS) AND INCREASED SHEAR, LEADING TO A RAPID EXTRATROPICAL TRANSITION BEGINNING AROUND TAU 96 THROUGH 120. MODEL DISCUSSION: THE SYSTEM'S ALONG-TRACK FORWARD SPEED DURING THE 72-120 HOUR VARIES EXTREMELY IN THE MODEL GUIDANCE DURING THE LATER TAUS, WITH THE VARIANCE BETWEEN NAVGEM AND GFS AT WELL OVER 850 NM BY TAU 120. THE JTWC TRACK FORECAST LIES CLOSE TO THE MULTI-MODEL CONSENSUS, BETWEEN THE LEFTWARD, SLOW ECMWF ENSEMBLE AND THE RIGHTWARD, FAST GFS. THE JTWC INTENSITY FORECAST IS SLIGHTLY BELOW THE MULTI-MODEL CONSENSUS THROUGH 48 HOURS, THEN CLOSE TO CONSENSUS THEREAFTER. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM 4. JUSTIFICATION FOR CORRECTION: ADJUSTED INITIAL RADII BASIS AND FOR CONFIDENCE LINE.// NNNN