WDPN32 PGTW 232100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (NORU) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.2N 129.3E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 504 NM EAST-NORTHEAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CENTRAL COLD COVER (CCC) WITH A SYMMETRIC REGION OF COLD UPPER-LEVEL CLOUDS OBSCURING THE LOW-LEVEL CIRCULATION CENTER, WHICH IS TUCKED UNDER THE NORTHERN EDGE OF THE CCC. A RECENTLY RECEIVED 231708Z AMSR2 89GHZ COLOR COMPOSITE MICROWAVE IMAGE REVEALS TIGHTLY-WRAPPED LOW-LEVEL BANDING WRAPPING INTO A WELL-DEFINED CENTER WITH CURVED CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE. BASED ON THIS IMAGE, THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE AND IS ABOUT 18NM TOO FAR NORTH. CCC INDICATES ARRESTED DEVELOPMENT THUS THE INITIAL INTENSITY IS HELD AT 45 KTS WITH MEDIUM CONFIDENCE. THE AFOREMENTIONED 231708Z AMSR2 WINDSPEED IMAGE INDICATED PEAK WINDS OF 35 KNOTS OVER THE SOUTH QUADRANT, WHICH FALLS WITHIN THE RANGE OF DVORAK INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH MODERATE WESTWARD OUTFLOW, ENHANCED BY AN UPPER-LOW OVER THE SOUTH CHINA SEA, AND LOW VERTICAL WIND SHEAR (VWS). INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS KNES: T3.0 - 45 KTS CIMSS SATCON: 40 KTS AT 231718Z CIMSS ADT: 35 KTS AT 231750Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 0-5 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM 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 18W IS FORECAST TO TRACK WEST-SOUTHWESTWARD ALONG THE SOUTHWEST PERIPHERY OF THE STR THROUGH TAU 24 THEN TURN MORE WESTWARD AS IT APPROACHES LUZON WITH LANDFALL NEAR TAU 36. DUE TO THE FAVORABLE CONDITIONS, END OF THE CCC (ARRESTED DEVELOPMENT) STAGE AND DECREASE IN VWS OVER THE PAST 12 HOURS, TS 18W IS EXPECTED TO INTENSIFY QUICKLY PRIOR TO LANDFALL TO AN INTENSITY OF 65 TO 70 KNOTS. AFTER TRANSITING ACROSS LUZON, TS 18W WILL RE-EMERGE OVER THE SOUTH CHINA SEA AND WILL COMMENCE A RE-INTENSIFICATION PHASE AS IT TRACKS WESTWARD TOWARD AND OVER VIETNAM AND SOUTHEAST ASIA. PEAK INTENSITY IS EXPECTED BETWEEN TAU 72 AND TAU 96, WHEN LANDFALL OCCURS. RAPID WEAKENING WILL OCCUR AS THE SYSTEM TRACKS INLAND. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD WITH A 70NM TO 110NM SPREAD IN SOLUTIONS FROM TAU 72 TO TAU 96 LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. RAPID INTENSIFICATION IS POSSIBLE PRIOR TO LANDFALL WITH THE TRIGGERING OF RAPID INTENSIFICATION (RI) GUIDANCE AND UP TO 85 PERCENT PROBABILITY OF RI INDICATED IN THE 231200Z COAMPS-TC ENSEMBLE GUIDANCE. COAMPS-TC ALSO SHOWS A 20 TO 50 PERCENT PROBABILITY OF RI IN THE SOUTH CHINA SEA, WHICH IS LIKELY DURING THE 251800Z TO 270600Z PERIOD. HWRF INDICATES A PEAK OF 90 KNOTS AT TAU 84 (270600Z) AS WELL. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN