WDPN31 PGTW 170300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.0N 150.4E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 449 NM NORTHEAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY CONSOLIDATING TROPICAL STORM (TS) 24W, WITH VORTICAL HOT TOWERS EMBEDDED WITHIN A COMPACT CENTRAL DENSE OVERCAST AND SPIRAL BANDING DEVELOPING ALONG THE NORTHERN AND SOUTHEASTERN PERIPHERIES. THE COLDEST CLOUD TOP TEMPERATURES MEASURED NEAR -88 DEGREES CELSIUS. UPPER-LEVEL OUTFLOW HAS IMPROVED SIGNIFICANTLY, VENTING RADIALLY OUTWARD. TS 24W IS LOCATED NEAR THE SOUTHERN END OF A MERIDIONALLY ORIENTED SURFACE TROUGH, WHILE AN UPPER-LEVEL TROUGH POSITIONED NEAR THE FAR NORTHERN MARIANA ISLANDS SUPPRESSES CONVECTION ALONG THE WESTERN PERIPHERY. THE SYSTEM REMAINS IN A FAVORABLE ENVIRONMENT OF VERY WARM SEA SURFACE TEMPERATURES (SST), LOW VERTICAL WIND SHEAR (VWS), AND IMPROVING OUTFLOW ALOFT. A TIMELY 162235Z ASCAT-B PASS REVEALED AN ASYMMETRIC, COMPACT STORM-FORCE WIND CORE, WITH GALE-FORCE WINDS EXTENDING UP TO 150 NM OUTWARD. THE SCATTEROMETER DATA AND THE CONTINUED IMPROVEMENT IN THE CONVECTIVE STRUCTURE SUPPORT RAISING THE INITIAL INTENSITY TO 50 KTS WITH HIGH CONFIDENCE. THIS ASSESSMENT IS HIGHER THAN THE SUBJECTIVE AND OBJECTIVE ESTIMATES, WHICH MAY TEND TO UNDERREPRESENT THE INTENSITY OF A RAPIDLY CONSOLIDATING, COMPACT INNER CORE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE ROTATING MOTION OF THE HOT TOWERS IN MSI AND THE ASCAT-B WIND FIELD. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: SOUTHERN EXTENSION OF A SUBTROPICAL RIDGE (STR) CENTERED NEAR 38N 165E AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T3.0 - 45 KTS RCTP: T2.5 - 35 KTS CIMSS SATCON: 41 KTS AT 162011Z CIMSS ADT: 39 KTS AT 162330Z CIMSS AIDT: 44 KTS AT 170030Z CIMSS D-MINT: 41 KTS AT 162010Z CIMSS D-PRINT: 38 KTS AT 162300Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 24W IS ACCELERATING POLEWARD ALONG THE WESTERN PERIPHERY OF A STR CENTERED EAST OF HONSHU. FROM TAU 24 TO TAU 48, THE RIDGE WILL BUILD WESTWARD, RESULTING IN A SLOWER, MORE WESTWARD TRAJECTORY. FROM TAU 48 TO TAU 72, THE SYSTEM WILL TURN POLEWARD AS IT ROUNDS THE STR, CROSS THE RIDGE AXIS, AND ACCELERATE NORTHEASTWARD AS IT COMES UNDER THE INFLUENCE OF DEEP-LAYER MID-LATITUDE WESTERLY FLOW. TS 24W WILL REMAIN IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW VWS, VERY WARM SST, AND MODERATE DIVERGENCE ALOFT. HOWEVER, AFTER A 20-KT INCREASE IN INTENSITY OVER THE PAST 18 HOURS, RECENT SATELLITE IMAGERY INDICATES THAT DEVELOPMENT MAY BE SLOWING AS THE ASYMMETRIC STRUCTURE TEMPORARILY CONSTRAINS FURTHER INTENSIFICATION. THEREFORE, THE FORECAST CALLS FOR A SLOWER RATE OF INTENSIFICATION OVER THE NEXT 24 HOURS. FROM TAU 24 TO TAU 48, MODERATE VWS WILL LIMIT ADDITIONAL INTENSIFICATION. BY TAU 48, A POLEWARD OUTFLOW CHANNEL WILL OPEN AS THE SYSTEM APPROACHES THE STR AXIS, SUPPORTING A SECOND ROUND OF MODEST INTENSIFICATION. ONCE THE VORTEX ROUNDS THE AXIS AT TAU 72, GRADUAL WEAKENING WILL COMMENCE AS INCREASING VWS MORE THAN OFFSETS THE DEVELOPMENTAL BENEFITS OF ENHANCED POLEWARD OUTFLOW. TS 24W WILL UNDERGO EXTRATROPICAL TRANSITION TOWARD THE END OF THE FORECAST PERIOD AS IT ENCOUNTERS A STRONGER BAROCLINIC ENVIRONMENT. MODEL DISCUSSION: THE TRACK GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH TAU 120, THOUGH ALONG-TRACK SPREAD BEGINS TO INCREASE AFTER TAU 72. THE AI MODELS LIE FARTHER WEST THAN THE PHYSICS-BASED MODELS. THE JTWC FORECAST TRACK IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS (CONW) WITH HIGH CONFIDENCE THROUGH TAU 72. AFTER TAU 72, TRACK CONFIDENCE DECREASES TO MEDIUM AS THE AI MODELS DIVERGE SLIGHTLY FROM THE CONSENSUS, WITH THE FORECAST TRACK FAVORING A BLEND OF THE AI SOLUTIONS AND THE CONSENSUS. HAFS-A, GFS, AND ECMWF ARE THE EASTERNMOST SOLUTIONS AT TAU 96 AND TAU 120. THE INTENSITY AIDS HAVE BECOME HIGHLY DIVERGENT THIS CYCLE. MULTIPLE RAPID INTENSIFICATION (RI) AIDS HAVE AGAIN TRIGGERED. HOWEVER, GIVEN THE SLOWING IMPROVEMENT IN THE SATELLITE PRESENTATION, THESE AIDS ARE DISCOUNTED. THE DYNAMICAL MODELS ARE MIXED, WITH GFS AND HAFS-A SHOWING A NEAR-STEADY INTENSITY THROUGH TAU 120 AND COAMPS-TC DEPICTING MODEST INTENSIFICATION TO TYPHOON INTENSITY. GIVEN THAT THESE AID SOLUTIONS REPRESENT A SIGNIFICANT DEPARTURE FROM THE PRIOR CYCLE, ONLY MINIMAL CHANGES WERE MADE TO THE JTWC INTENSITY FORECAST. TWO DISTINCT SCENARIOS ARE POSSIBLE. IF THE SYSTEM MAINTAINS A COMPACT CORE THROUGH THE NEXT 72 HOURS, IT COULD ATTAIN A MUCH HIGHER PEAK INTENSITY THAN CURRENTLY FORECAST. THIS PATHWAY WAS DEPICTED IN THE PRIOR HAFS-A SOLUTION. THE ALTERNATE SCENARIO, TOWARD WHICH THIS FORECAST LEANS, IS THAT THE COMPACT CORE BROADENS INTO THE LARGER PRE-EXISTING CIRCULATION. THIS EVOLUTION WOULD LIMIT THE SYSTEM'S PEAK INTENSITY. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN