MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (KUJIRA) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 15W (KUJIRA), LOCATED APPROXIMATELY 150 NM NORTH OF MINAMI TORI SHIMA, HAS TRACKED NORTHWESTWARD AT 21 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTIVE BANDING WRAPPING INTO THE CENTER FROM THE NORTH AND WEST. A 272301Z ASCAT-C PASS REVEALS A WELL-DEFINED CIRCULATION WITH AN AREA OF 40-44KT WINDS TO THE EAST WITH WEAKER WINDS ELSEWHERE. BASED ON THE ASCAT AND PARTIALLY-EXPOSED LLCC, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 40 KTS BASED ON THE AFOREMENTIONED ASCAT DATA AND 272014Z SMAP DATA SHOWING 35 KT 10-MINUTE AVERAGE WINDS (APPROXIMATELY 39 KT 1-MINUTE AVERAGE WINDS). FURTHERMORE, THE INITIAL INTENSITY IS HEDGED BETWEEN DVORAK CURRENT INTENSITY ESTIMATES OF T2.5-3.0(35-45 KTS, RJTD/PGTW), AN ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.5 (35 KTS), AND A 272145Z SATCON ESTIMATE OF 47 KTS WITH GOOD CONFIDENCE. ALL WIND RADII HAVE BEEN UPDATED WITH RECENT ASCAT DATA. UPPER LEVEL ANALYSIS REVEALS IMPROVED POLEWARD OUTFLOW ENHANCED BY THE APPROACHING SHORTWAVE TROUGH AND DIMINISHED EQUATORWARD OUTFLOW DUE TO CONVERGENT FLOW FROM AN UPPER LOW POSITIONED SOUTHWEST OF THE SYSTEM. SUPPORTED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS) AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES, THE SYSTEM IS TRANSITING THROUGH AN OVERALL MARGINALLY FAVORABLE ENVIRONMENT. TS 15W IS TRACKING NORTHWESTWARD UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 15W IS FORECAST TO TRACK NORTH-NORTHWESTWARD THROUGH TAU 12 WITH STEADY INTENSIFICATION THEN TURN GENERALLY NORTHWARD AS IT BEGINS TO ROUND THE STR. THROUGH TAU 36, THE SYSTEM SHOULD CONTINUE TO INTENSIFY DUE TO ENHANCED POLEWARD OUTFLOW ASSOCIATED WITH THE SHORTWAVE TROUGH DIGGING SOUTH OF JAPAN, PEAKING THE SYSTEM TO 65 KTS BY TAU 36. EXTRATROPICAL TRANSITION (ETT) IS EXPECTED TO BEGIN NEAR TAU 36 AS TS 15W RECURVES INTO THE MIDLATITUDE WESTERLIES. FOLLOWING THIS, TS 15W WILL STEADILY WEAKEN AS IT ENCOUNTERS INCREASING VWS (25-35 KTS) AND TRACKS OVER COOLING SEA SURFACE TEMPERATURES. THE SYSTEM IS EXPECTED TO COMPLETE ETT NEAR TAU 72, IF NOT SOONER, AS IT GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED WITHIN THE MIDLATITUDE WESTERLIES. NUMERICAL MODEL GUIDANCE AND THE ECMWF ENSEMBLE SOLUTIONS REMAIN IN EXCELLENT AGREEMENT THROUGHOUT THE FORECAST PERIOD. THUS, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN