WDPN31 PGTW 261500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI) WARNING NR 025// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.2N 110.8E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 161 NM EAST-NORTHEAST OF DA NANG, VIETNAM MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 32 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL STORM (TS) 22W CONTINUES TO STRUGGLE UNDER HIGH EASTERLY VERTICAL WIND SHEAR (VWS), WITH CORE CONVECTION BECOMING MORE LINEAR AND DISPLACED OVER THE WESTERN QUADRANT. A 261104Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE IMAGE REVEALS A DEFINED, BROAD LOW-LEVEL CIRCULATION CENTER, WITH CURVED CONVECTIVE BANDING OVER THE WESTERN QUADRANT. DESPITE THE HIGH VWS, DEEP CONVECTION IS PERSISTING DUE TO MODERATE WESTERLY OUTFLOW. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SSMIS IMAGE. THE INITIAL INTENSITY IS ASSESSED AT 55 KNOTS, CONSISTENT WITH THE DEGRADED CONVECTIVE STRUCTURE, IS BASED ON THE LOWER END OF THE AGENCY DVORAK ESTIMATES AND RECENT CIMSS ADT, AIDT OBJECTIVE ESTIMATES. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.0 - 65 KTS RJTD: T3.5 - 55 KTS KNES: T3.5 - 55 KTS DEMS: T4.0 - 65 KTS CIMSS ADT: 53 KTS AT 261200Z CIMSS AIDT: 57 KTS AT 261200Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 25-30 KTS SST: 27-28 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: TROPICAL STORM (TS) 22W WILL CONTINUE TRACKING WESTWARD THROUGH TAU 12 ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE NORTH. THE SYSTEM WILL WEAKEN STEADILY DUE TO PERSISTENT HIGH (25-30 KNOTS) VERTICAL WIND SHEAR. AFTER TAU 12, THE STR WILL WEAKEN AS UPPER-LEVEL WESTERLIES SHIFT INTO SOUTHERN CHINA WEAKENING THE STR TO THE NORTH WHILE ANOTHER STR OVER THE BAY OF BENGAL EFFECTIVELY BLOCKS ANY FURTHER WESTWARD PROGRESSION. CONSEQUENTLY, THE SYSTEM WILL SLOW SIGNIFICANTLY AND STALL NEAR THE COAST OF CENTRAL VIETNAM, WHICH WILL RESULT IN FURTHER WEAKENING DUE TO FRICTIONAL EFFECTS. AFTER TAU 36, TS 22W WILL TRACK EASTWARD ALONG THE NORTHERN PERIPHERY OF A BELT OF LOW-LEVEL WESTERLIES THAT FEED INTO THE APPROACHING TROPICAL CYCLONE (23W), WITH STEADY DEVELOPMENT AND POSSIBLE DISSIPATION BY TAU 120. MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ONLY THROUGH TAU 12, WITH INCREASING HIGH UNCERTAINTY AFTER TAU 12 AS THE SYSTEM WEAKENS AND THE PRIMARY STEERING INFLUENCE TO THE NORTH WEAKENS. PROBABILISTIC GUIDANCE REVEALS A SIMILAR DEGREE OF UNCERTAINTY BUT ALSO CONFIRMS THE RAPID WEAKENING OF THE SYSTEM THROUGH THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN