WDPN31 PGTW 220900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 14.0N 126.6E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 328 NM EAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTIVE BANDING OVER THE WESTERN SEMICIRCLE WRAPPING INTO THE SOUTHERN QUADRANT OF AN EXPOSED, BROAD LOW-LEVEL CIRCULATION CENTER. AS REVEALED IN A 220148Z MHS 89GHZ MICROWAVE IMAGE, THE BULK OF THE DEEP CONVECTIVE BANDING IS DISPLACED OVER THE SOUTHWESTERN QUADRANT DUE TO NORTHEASTERLY VERTICAL WIND SHEAR. A RECENT SCATTEROMETER IMAGE DEPICTS AN ELONGATED CENTER, WHICH SUPPORTS THE INITIAL POSITION, WITH A SWATH OF 35-40 KNOT WINDS OVER THE SOUTHERN SEMICIRCLE AND WEAKER WINDS ELSEWHERE. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE NORTHEASTERLY VERTICAL WIND SHEAR OFFSET BY MODERATE WESTWARD VENTING, WHICH IS SUSTAINING DEEP CONVECTION AND CURVED BANDING OVER THE WESTERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI AND THE AFOREMENTIONED SCATTEROMETER IMAGE. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY SUBJECTIVE DVORAK ESTIMATES RANGING FROM 2.0 TO 2.5 (30-35 KNOTS). INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH-NORTHEAST. 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: 40 KTS AT 220233Z CIMSS ADT: 34 KTS AT 220530Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: TROPICAL STORM (TS) 22W IS FORECAST TO TRACK WEST-NORTHWESTWARD THROUGH TAU 24 ALONG THE SOUTHWESTERN PERIPHERY OF THE STR, TOWARD A BREAK IN THE STR PRODUCED BY A MIDLATITUDE SHORTWAVE TROUGH DIGGING INTO THE EAST CHINA SEA. AFTER TAU 24, THE STR WILL REBUILD TO THE NORTH TURNING THE SYSTEM ONTO A MORE WESTWARD TRAJECTORY. THE SYSTEM WILL INTENSIFY SLIGHTLY BEFORE LANDFALL UNDER THE MARGINALLY FAVORABLE CONDITIONS. LANDFALL OVER EASTERN LUZON WILL OCCUR NEAR TAU 30, WITH SIGNIFICANT WEAKENING COMMENCING. AFTER TAU 36, TS 22W WILL WEAKEN AND DECOUPLE WHILE CROSSING THE RUGGED TERRAIN OF LUZON, WITH A LIKELY LEESIDE JUMP. THIS WILL RESULT IN AN APPARENT DIP IN THE FORECAST TRACK AS A NEW PRESSURE CENTER FORMS AND STRENGTHENS OFF THE WEST COAST OF LUZON NEAR TAU 48. AFTER TAU 48, THE SYSTEM WILL RESUME A WESTWARD TRACK UNDER THE STR TO THE NORTH WITH STEADY INTENSIFICATION TO ABOUT 60 KNOTS BY TAU 96. MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD, WITH AN 80NM TO 90NM CROSS- TRACK SPREAD FROM TAU 72 TO TAU 120. PROBABILISTIC GUIDANCE INDICATES A WIDER SPREAD OF SOLUTIONS FROM NORTHERN HAINAN ISLAND TO ABOUT 17N LATITUDE SUGGESTING A LIKELY LANDFALL OVER CENTRAL VIETNAM JUST AFTER TAU 120. RELIABLE INTENSITY GUIDANCE SHOWS A PEAK INTENSITY AT TAU 84 RANGING FROM 55 KNOTS (HAFS-A) TO AS HIGH AS 71 KNOTS (HWRF). FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN