WDPN32 PGTW 290300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.8N 133.7E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 668 NM SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A POORLY ORGANIZED MEDIUM-SIZED SYSTEM WITH CONVECTION CONCENTRATED SOUTHWARD OF A BROAD AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION (LLC). THE NORTHWEST QUADRANT IS VOID OF ANY DEEP CONVECTION AND THE MSI LOOP SHOWS COLD DRY AIR STRATOCUMULUS LINES FEEDING INTO THE LLC. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTLY EXPOSED LLC AND LINED UP WITH A MICROWAVE LLC IN THE 282240Z GPM 37GHZ AND 89GHZ IMAGE. THE INITIAL INTENSITY OF 40 KTS IS ALSO PLACED AT WITH MEDIUM CONFIDENCE BASED ON THE ASSESSMENT OF THE 282117Z SMAP DATA AND SUPPORTED BY CIMSS SATCON DVORAK ESTIMATE OF 42KTS AND REFLECTS THE SLIGHT 6-HR IMPROVEMENT. ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH WARM SST IN THE PHILIPPINE SEA, LOW VWS, AND STRONG POLEWARD OUTFLOW ALOFT OFFSET BY UPPER LEVEL SUBSIDENCE ALONG THE NORTHWEST QUADRANT DUE TO PRESSURE FROM THE SUBTROPICAL HIGH TO THE NORTHWEST AND THE INFLUX OF COLD DRY AIR AT THE LOW LEVELS. INITIAL WIND RADII BASIS: SMAP DATA. CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER NEAR EQUATORIAL RIDGE (NER) CENTERED EAST OF GUAM. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 42 KTS AT 282214Z CIMSS ADT: 33 KTS AT 282330Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM 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 KHANUN WILL CONTINUE ON A NORTH-NORTHWESTWARD TRACK UNDER THE STEERING INFLUENCE OF THE NER EAST OF GUAM. AFTER TAU 36, A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST WILL ASSUME STEERING AND DRIVE THE SYSTEM ON A MORE NORTHWESTWARD TRAJECTORY TOWARD OKINAWA, PASSING JUST WEST OF THE ISLAND AROUND TAU 60 PRIOR TO DRIFTING INTO THE EAST CHINA SEA AND MAKING LANDFALL SOUTH OF SHANGHAI AROUND TAU 96. THE MARGINALLY FAVORABLE ENVIRONMENT WILL FUEL A SLOW INTENSIFICATION TO 65KTS BY TAU 36. AFTERWARD, INCREASING POLEWARD OUTFLOW AS THE STEERING MECHANISM SWITCHES TO THE STR WILL PROMOTE SIGNIFICANT A MORE GRADUAL TO A PEAK OF 85KTS BY TAU 72. AFTER TAU 72, A BUILDING STR TO THE NORTH WILL ONCE AGAIN PROMOTE SUBSIDENCE LEADING TO GRADUAL WEAKENING TO 70 KTS AT LANDFALL. AFTER LANDFALL, INTERACTION WITH THE RUGGED CHINESE INTERIOR WILL MOSTLY BE RESPONSIBLE FOR THE RAPID EROSION, AND BY TAU 120, TC 06W WILL BE REDUCED TO 45KTS, POSSIBLY WEAKER, AS IT TRACKS FURTHER INLAND. MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT WITH A GRADUAL SPREAD TO A MERE 190NM BY TAU 72 THEN TO 486 NM BY TAU 120 WITH UKMET THE NOTABLE LEFT-OF-TRACK OUTLIER. IN VIEW OF THIS, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK THAT IS LAID JUST TO THE RIGHT OF THE MODEL CONSENSUS TO OFFSET UKMET UP TO TAU 72 THEN MEDIUM CONFIDENCE AFTERWARD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN