MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (BAVI) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 09W (BAVI), LOCATED APPROXIMATELY 331 NM WEST- SOUTHWEST OF KADENA AB, OKINAWA, HAS TRACKED NORTH-NORTHEASTWARD AT 06 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY AND ANIMATED RADAR IMAGERY REVEAL A PARTIALLY-EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION OVER THE EASTERN SEMICIRCLE OF THE SYSTEM. A 212313Z SSMIS 89 GHZ PARTIAL MICROWAVE IMAGE SHOWS SHALLOW BANDING WRAPPING INTO THE CENTER FROM THE WEST AND CONFIRMS THE DEEP CONVECTION TO THE SOUTH AND EAST. SET AT 35 KTS, THE INITIAL INTENSITY IS BASED ON A SATELLITE CONSENSUS ESTIMATE OF 34 KTS AND MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T1.5-T2.0 (25-30 KTS) BY PGTW, RJTD, AND KNES. FURTHERMORE, A 220055Z PARTIAL ASCAT-B IMAGE DEPICTS A SWATH OF 35- 39 KT WINDS SURROUNDED BY 30-34 KT WINDS IN THE EASTERN QUADRANT, PLACING GOOD CONFIDENCE IN THE INITIAL INTENSITY. TS 09W REMAINS IN A HIGHLY FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR, WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES, AND HIGH OCEAN HEAT CONTENT VALUES. ADDITIONALLY, THE SYSTEM IS SUPPORTED BY EXCELLENT EQUATORWARD OUTFLOW AND DEVELOPING POLEWARD OUTFLOW WHICH IS BEING ENHANCED BY AN UPPER LOW TO THE NORTHEAST. A SUBTROPICAL RIDGE (STR) TO THE EAST WITH A SLIGHT WEAK EXTENSION TO THE NORTH IS ACTING AS THE PRIMARY STEERING FEATURE. CURRENTLY, TS 09W IS TRACKING NORTH-NORTHWESTWARD ALONG ITS PERIPHERY. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. AS A PASSING SHORTWAVE TROUGH DIGS OVER THE EAST CHINA SEA, THE WEAK STR EXTENSION IS EXPECTED TO ERODE WHICH WILL CAUSE THE STR TO REORIENT. BY TAU 24, TS 09W IS FORECAST TO TURN NORTHEASTWARD AND TRACK ALONG THE PERIPHERY OF THE REORIENTED STR. THE FAVORABLE ENVIRONMENT WILL CONTINUE TO INTENSIFY THE SYSTEM THROUGHOUT THIS PERIOD. AFTER TAU 48, TS 09W IS EXPECTED TO SLOW AS IT TURNS TO NORTHWARD FOLLOWING TROUGH PASSAGE. THE TROUGH PASSAGE IS EXPECTED TO ENHANCE POLEWARD OUTFLOW, ALLOWING THE SYSTEM TO INTENSIFY TO 95 KTS BY TAU 72. DYNAMIC MODEL GUIDANCE IS IN FAIR AGREEMENT, GRADUALLY INCREASING TO A SPREAD OF 150 NM BY TAU 72 AS THE SYSTEM RECURVES TO THE NORTH. C. IN THE EXTENDED FORECAST, A STR WILL BUILD OVER WESTERN JAPAN AFTER THE TROUGH PROPAGATES EASTWARD. AT THIS POINT, TS 09W WILL TURN NORTHWARD ALONG THE WESTERN PERIPHERY OF THE STR UNTIL LANDFALL IN SOUTH KOREA AFTER TAU 96. A FAVORABLE ENVIRONMENT WILL ALLOW TS 09W TO INTENSIFY TO A PEAK OF 105 KTS BY TAU 96. AFTERWARDS, DEGRADING ENVIRONMENTAL CONDITIONS OF INCREASING VERTICAL WIND SHEAR AND INTERACTION WITH THE KOREAN PENINSULA WILL WEAKEN THE SYSTEM, FIRST GRADUALLY AND THEN RAPIDLY. A 140 NM SPREAD IN MODELS AT TAU 96 LENDS UNCERTAINTY TO THE LANDFALL LOCATION. HOWEVER, THE NUMERICAL MODELS ARE IN OVERALL FAIR AGREEMENT, LENDING MODERATE CONFIDENCE TO THE JTWC FORECAST TRACK.// NNNN NNNN