WDPN33 PGTW 142100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (NANMADOL) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 23.1N 139.8E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 131 NM SOUTHWEST OF IWO TO MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 19 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS CONTINUING IMPROVEMENT AND CONSOLIDATION OF BROAD FLARING CONVECTIVE BANDING WRAPPING AROUND THE SYSTEM INTO A DEEPENING LOW LEVEL CIRCULATION CENTER (LLCC). SATELLITE IMAGERY ALSO REVEALS THAT 16W HAS MADE THE LEFT TURN WHILE INCREASING TRACK SPEED AS IT TRANSITS WEST-NORTHWEST. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON AN EARLIER EXTRAPOLATED 131141Z METOP-C ASCAT, ALONG WITH A COMBINATION OF AGENCY FIX POSITIONS FROM PGTW, KNES, AND RJTD. THE INITIAL INTENSITY IS PLACED WITH HIGH CONFIDENCE BASED ON THE IMPROVED SATELLITE DEPICTION, ALONG WITH THE PGTW DVORAK ESTIMATE OF T3.0, WITH THE LATEST CIMSS SATCON VALUE COMING IN AT 53 KNOTS. THEREFORE, THE CURRENT INTENSITY IS UPGRADED TO 50 KNOTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: THE SUBTROPICAL RIDGE TO THE NORTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T3.5 - 55 KTS KNES: T4.0 - 65 KTS CIMSS SATCON: 53 KTS AT 141810Z CIMSS ADT: 47 KTS AT 141740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 0-5 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: DEEP TROPICAL MOISTURE INFLOW ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH 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 16W (NANMADOL) IS FORECAST TO TRACK NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) WHICH WILL REMAIN THE DOMINATE STEERING FEATURE TO THE NORTH. THE ENVIRONMENTAL FACTORS ARE CONDUCIVE FOR FURTHER DEVELOPMENT CHARACTERIZED BY LOW (0-5 KTS) VERTICAL WIND SHEAR (VWS), WARM (29-30C) SEA SURFACE TEMPERATURES (SSTS) AND MODERATE RADIAL OUTFLOW. THESE FACTORS WILL ALLOW 16W TO CONTINUE A STEADY INCREASE IN INTENSIFICATION BEFORE REACHING A POTENTIAL MAXIMUM INTENSITY OF 105 KNOTS BY TAU 72, WHILE THE SYSTEM ROUNDS THE SUBTROPICAL RIDGE AXIS AND TURNS NORTH-NORTHWEST. BETWEEN TAU 72 AND TAU 96 TS 16W WILL BEGIN TO SLOW IN TRACK SPEED, AS MANY MODEL TRACKERS INDICATE A POSSIBLE RECURVE SCENARIO WITH SOME SPREAD OF 125 NM. ADDITIONALLY, THE JTWC FORECAST CALLS FOR A DECREASE IN INTENSITY TO 80 KNOTS LIKELY DUE TO THE AFFECT OF LAND INTERACTION ALONG WITH AN INCREASE IN VERTICAL WIND SHEAR (VWS), AS DECAY SHIPS GUIDANCE INDICATES UP TO 15 KNOTS. BETWEEN TUA 96 AND TAU 120, THE SYSTEM IS FORECAST TO CONTINUE TO RECURVE AS 16W MOVES POLEWARD OF THE RIDGE AXIS AND BECOMES EMBEDDED IN AN APPROACHING UPPER LEVEL TROUGH WHICH WOULD INCREASE ITS TRACK SPEED TO THE NORTHEAST. HOWEVER, THERE IS UNCERTAINTY IN THE TIMING OF THE INTERACTION WITH THE APPROACHING UPPER LEVEL TROUGH AND HOW FAST THE SUBTROPICAL RIDGE TO THE EAST ERODES. THESE FACTORS WILL HAVE A LARGE IMPACT ON THE TRACK MOTION AND TRACK SPEED BY THE END OF THE FORECAST. MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT THROUGH TAU 72 WITH ONLY AN 80NM SPREAD IN SOLUTIONS. BY TAU 96 THE CONSENSUS SPREAD INCREASES TO 125NM. BEYOND TAU 96, UNCERTAINTY INCREASES WITH DIFFERENCES IN THE TIMING AND POSITION OF A POSSIBLE RECURVATURE WITH MODEL TRACKERS DIVERGING GREATLY. FOR EXAMPLE, THE LATEST GFS NUMERICAL MODEL GUIDANCE SHOWS A SLOW DOWN IN TRACK SPEED TO A POSSIBLE QUASI-STATIONARY SOLUTION TO THE SOUTHWEST OF JAPAN. WHILE OTHER MODELS SUCH AS ECMWF, UKMO, AND GALWEM TAKE A SHARPER TURN TOWARDS HONSHU WHILE INCREASING IN TRACK SPEED BY TAU 120. GIVEN THESE TWO POSSIBLE SCENARIOS UNCERTAINTY REMAINS HIGH IN THE TRACK FORECAST FROM TAU 96 THROUGH TAU 120. RELIABLE INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH ALL MEMBERS SHOWING A STEADY INTENSIFICATION THROUGH TAU 72. HOWEVER, RAPID INTENSIFICATION IS A POSSIBILITY OVER THE NEXT 36 TO 72 HOURS, AND WILL CONTINUE TO BE MONITORED FOR THE POSSIBILITY WITH AN ADJUSTMENT IN THE MAXIMUM INTENSITY AS MORE GUIDANCE BECOMES AVAILABLE. FROM TAU 96 THROUGH 120, THE FORECAST INTENSITY CONFIDENCE IS LOW GIVEN THE UNCERTAINTY AND DIFFERENCES IN THE TIMING AND SPEED OF THE INTERACTION WITH LARGE SCALE STEERING FEATURES AS WELL AS LAND INTERACTION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN