WDPN31 PGTW 030900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 27.0N 129.0E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 71 NM EAST-NORTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL STORM (TS) 22W. CONVECTION PERSISTS ONLY ALONG THE SOUTHERN SEMICIRCLE DUE TO THE PRESENCE OF DRY AIR AND MODERATE NORTHWESTERLY VERTICAL WIND SHEAR. THE UPPER-LEVEL OUTFLOW IS WEAK AND PRIMARILY EQUATORWARD AS THE SYSTEM STRUGGLES TO COUNTERACT THE EFFECTS OF SHEAR AND AN OVERHEAD TROUGH. THE ENVIRONMENT IS MARGINAL, WITH TS 22W TRAVERSING WATERS WITH SEA SURFACE TEMPERATURES (SST) OF 27-29 DEGREES CELSIUS AND EXPERIENCING 15-20 KTS OF VWS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MSI. A 030003Z ASCAT-B PASS REVEALED AN EXTENSIVE AREA OF 35-40 KT WINDS ALONG THE EASTERN PERIPHERY, WITH A BROAD CORE OF LIGHT WINDS NEAR THE CENTER. AS THE CONVECTIVE STRUCTURE HAS NOT APPRECIABLY CHANGED SINCE THAT OBSERVATION, THE INITIAL INTENSITY HAS BEEN HELD AT 40 KTS WITH HIGH CONFIDENCE. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE SOUTHEAST OF JAPAN AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 42 KTS AT 030457Z CIMSS ADT: 35 KTS AT 030540Z CIMSS AIDT: 38 KTS AT 030540Z CIMSS D-MINT: 35 KTS AT 030458Z CIMSS D-PRINT: 36 KTS AT 030540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 15-20 KTS SST: 27-29 CELSIUS OUTFLOW: WEAK EQUATORWARD OTHER FACTORS: DRY AIR ON THE NORTH SIDE ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK FROM TAU 60 TO TAU 120 HAS SHIFTED WESTWARD BY 30-50 NM, NOW PLACING MOST OF OKINAWA WITHIN THE NORTHEAST QUADRANT OF THE CIRCULATION FROM TAU 48 TO TAU 72. FORECAST DISCUSSION: THE CENTER OF TS 22W HAS JOGGED SLIGHTLY WEST-NORTHWESTWARD OVER THE PAST SIX HOURS. THE SYSTEM WILL RESUME A GENERAL NORTHWESTWARD MOTION FOR THE NEXT 24 HOURS. A FAST-MOVING TROUGH PASSING OVER THE KOREAN PENINSULA WILL ALLOW A RIDGE TO BUILD OVER MAINLAND CHINA, INDUCING A NORTHEASTERLY SURGE OF COOL, DRY AIR EXTENDING FROM THE SURFACE TO 500 MB. THIS DEVELOPMENT WILL CAUSE TS 22W TO SLOW AND STALL BETWEEN TAU 24 AND TAU 36. AS THE RIDGE EXTENDS SOUTHEASTWARD, THE CIRCULATION WILL REVERSE COURSE AND TURN SOUTHEASTWARD. BY TAU 72, TS 22W WILL BE PICKED UP BY DEEP-LAYER SOUTHWESTERLY FLOW ASSOCIATED WITH BROAD CYCLONIC ROTATION DOMINATING THE REGION SOUTH OF HONSHU, TURNING EASTWARD AND THEN NORTHEASTWARD. THE FORECAST DEPICTS A SLIGHT WEAKENING TREND THROUGH TAU 24-36, FOLLOWED BY A NEAR-STEADY INTENSITY TREND THROUGH TAU 120. ENVIRONMENTAL CONDITIONS WILL REMAIN SIMILAR UNTIL THE SYSTEM STALLS AND ENCOUNTERS THE NORTHEASTERLY WIND SURGE NEAR TAU 24. THIS SURGE WILL SLIGHTLY WEAKEN THE SYSTEM BY INTRODUCING ADDITIONAL DRY AIR AND HIGHER VWS. AS TS 22W MOVES EQUATORWARD, THE VWS WILL EASE, AND THE MOISTURE PROFILE WILL IMPROVE. HOWEVER, THE BROAD CIRCULATION WILL REQUIRE TIME TO REORGANIZE, LIMITING THE POTENTIAL FOR SIGNIFICANT REINTENSIFICATION. THE FORECAST 34-KT WIND RADII DEPICT THE OUTER EXTENT OF GALE-FORCE WINDS. THROUGH TAU 60, SUCH WINDS WILL NOT EXTEND CONTINUOUSLY TO THE CENTER. DUE TO THE BROAD NATURE OF THE CIRCULATION, THE 34-KT WINDS BEGIN APPROXIMATELY 30-60 NM FROM THE CENTER. MODEL DISCUSSION: SIGNIFICANT UNCERTAINTIES EXIST IN THE LONG-TERM TRACK AND INTENSITY FORECAST DUE TO DIFFERENCES IN THE STRENGTH OF THE RIDGE THAT WILL EXTEND SOUTHEASTWARD, THE ORIENTATION OF THE SOUTHWESTERLY FLOW, AND POTENTIAL INTERACTION WITH THE DEVELOPING TROPICAL DISTURBANCE 97W TO THE EAST. THESE UNCERTAINTIES ARE REFLECTED IN THE INCREASING CROSS-TRACK SPREAD, WHICH EXPANDS FROM 150 NM AT TAU 60 TO 215 NM AT TAU 96 AND 300 NM AT TAU 120. TRACK GUIDANCE HAS ALSO SHIFTED WESTWARD, NECESSITATING A CORRESPONDING WESTWARD ADJUSTMENT TO THE JTWC FORECAST TRACK. AI-BASED MODELS PREFER A SHARPER 180-DEGREE REVERSAL, WHILE THE DYNAMICAL MODELS DEPICT A WIDER TURN. THEREFORE, THE JTWC FORECAST TRACK IS PLACED NEAR THE MULTI-MODEL CONSENSUS THROUGH TAU 72 WITH MEDIUM CONFIDENCE AND NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE THEREAFTER WITH LOW CONFIDENCE. THE JTWC INTENSITY FORECAST IS SET NEAR GFS, HAFS-A, AND THE EXPERIMENTAL GOOGLE DEEPMIND GUIDANCE WITH MEDIUM CONFIDENCE IN THE NEAR TERM AND LOW CONFIDENCE THEREAFTER. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN