MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (BAILU) WARNING NR 09// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 12W (BAILU), LOCATED APPROXIMATELY 417 NM SOUTH-SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEPENING CONVECTION WRAPPING COUNTERCLOCKWISE FROM THE SOUTHWEST TO NORTHEAST. THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE AND IS BASED ON A 230452Z AMSR2 36GHZ MICROWAVE IMAGE, WHICH SHOWS GOOD LOW LEVEL BANDING. THE INITIAL INTENSITY OF 45 KNOTS IS BASED ON DVORAK CURRENT INTENSITY (CI) ESTIMATES OF T3.0 FROM PGTW AND RJTD. THE INTENSITY OF 45 KNOTS IS ALSO SUPPORTED BY A 230428Z SATCON ESTIMATE OF 47 KNOTS. ENVIRONMENTAL ANALYSIS SHOWS THAT TS 12W IS EXPERIENCING FAVORABLE (5 TO 10 KNOT) VERTICAL WIND SHEAR. THE EQUATORWARD OUTFLOW CHANNEL REMAINS STRONG WHILE THERE IS LIMITED POLEWARD OUTFLOW. SEA SURFACE TEMPERATURES REMAIN FAVORABLE FOR ADDITIONAL DEVELOPMENT, BETWEEN 29 AND 30 DEGREES CELSIUS. TS 12W IS TRACKING NORTHWESTWARD WHILE UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. THE AFOREMENTIONED STR WILL CONTINUE TO BE THE PRIMARY STEERING FEATURE FOR THE REMAINDER OF THE FORECAST, ALLOWING TS 12W TO TRACK NORTHWESTWARD. FAVORABLE SEA SURFACE TEMPERATURES AND LOW VERTICAL WIND SHEAR WILL ALLOW TS 12W TO REACH 60 KNOTS BY TAU 24 AS IT PASSES JUST TO THE SOUTH OF TAIWAN. TS 12W WILL CONTINUE TO TRACK NORTHWESTWARD AROUND THE STR AND MAKE LANDFALL IN CHINA SHORTLY AFTER TAU 36. AFTER MAKING LANDFALL IN CHINA, TS 12W WILL QUICKLY DECREASE IN INTENSITY AND DISSIPATE BY TAU 72 WITH AN INTENSITY OF 20 KNOTS. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A MODEL SPREAD OF ONLY 130 NM BY TAU 72. THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN