MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (DOKSURI) WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 21W (DOKSURI), LOCATED APPROXIMATELY 255 NM WEST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A ROBUST CONVECTIVE MASS CENTRALLY LOCATED OVER A LOW LEVEL CIRCULATION CENTER (LLCC). A 122300Z 91 GHZ SSMIS MICROWAVE IMAGE SHOWS DEEP CONVECTIVE BANDING WRAPPING AROUND THE WESTERN SEMICIRCLE AND INTO A RAGGED MICROWAVE EYE FEATURE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE IMAGE. THE INITIAL INTENSITY OF 45 KNOTS IS HEDGED ON THE UPPER END OF MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM T2.5 TO T3.0 (35-45 KNOTS) FROM RJTD AND PGTW RESPECTIVELY. ENVIRONMENTAL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF LOW (10- 15 KNOTS) VERTICAL WIND SHEAR (VWS) AND IS TRACKING THROUGH VERY WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES (SSTS). THE OUTFLOW PATTERN HAS IMPROVED AS THE SYSTEM NOW HAS A STRONGER EQUATORWARD OUTFLOW CHANNEL AND HAS WEAK POLEWARD OUTFLOW. TS 21W IS TRACKING TO THE WEST-NORTHWEST UNDER THE INFLUENCE OF AN EXTENSION OF THE SUB- TROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 21W WILL CONTINUE TO TRACK WEST-NORTHWESTWARD UNDER THE INFLUENCE OF THE STR THROUGH TAU 72. THE IMPROVING ENVIRONMENT WILL ALLOW FOR A PERIOD OF RAPID INTENSIFICATION OVER THE NEXT 24 HOURS AS THE SYSTEM TRACKS THROUGH VERY WARM SSTS AND LOW VWS. THE SYSTEM IS FORECAST TO REACH A PEAK INTENSITY OF 80 KNOTS AT TAU 48. AFTER TAU 48, THE SYSTEM WILL BEGIN TO INTERACT WITH LAND AND START A GRADUAL WEAKENING TREND, MAKING LANDFALL IN NORTHERN VIETNAM, SOUTH OF HANOI, AROUND TAU 60. DYNAMIC MODEL GUIDANCE IS IN STRONG AGREEMENT LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST. C. PRIOR TO TAU 72, TS 21W WILL REMAIN OVER LAND AND CONTINUE TO TRACK TO THE WEST-NORTHWEST UNDER THE INFLUENCE OF A STR LOCATED OVER CENTRAL CHINA. THE SYSTEM IS FORECAST TO REMAIN OVER LAND AND RAPIDLY WEAKEN, COMPLETELY DISSIPATING BY TAU 96 DUE TO INTERACTION WITH THE RUGGED TERRAIN OF SOUTHEAST ASIA. DYNAMIC MODEL GUIDANCE IS IN GOOD OVERALL GENERAL AGREEMENT, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.// NNNN NNNN