WDPN31 PGTW 311500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W WARNING NR 18// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 07W (LIONROCK), LOCATED APPROXIMATELY 125 NM SOUTH-SOUTHWEST OF KAOHSIUNG, TAIWAN, HAS TRACKED EAST- NORTHEASTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED INFRARED SATELLITE IMAGERY SHOWS A FULLY EXPOSED LOW LEVEL CIRCULATION (LLCC) NORTHEAST OF THE DEEP CONVECTION. THE INITIAL INTENSITY IS BASED ON DVORAK ESTIMATES FROM PGTW AND KNES RANGING FROM 45 TO 55 KNOTS. TS 07W IS CURRENTLY UNDER MODERATE NORTHEASTERLY VERTICAL WIND SHEAR CAUSING THE LLCC AND THE CONVECTION TO DECOUPLE. TS 07W IS TRACKING ALONG THE LOW TO MID LEVEL RIDGE EXTENSION TO THE SOUTHEAST AND UNDER THE INFLUENCE OF DIRECT CYCLONE INTERACTION (DCI) WITH TS 09W. 3. FORECAST REASONING. A. OVERALL, THE FORECAST REASONING IS THE SAME AS IN THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THIS FORECAST TURNS TS 07W NORTHWESTWARD LATER THAN PREVIOUSLY EXPECTED. THIS FORECAST ALSO DECREASES MAXIMUM INTENSITY DUE TO AN INCREASE IN VERTICAL WIND SHEAR CAUSING AN EXPOSED LLCC. B. TS 07W IS EXPECTED TO CONTINUE TRACKING EAST-NORTHEASTWARD TO NORTHWARD AND THEN BEGIN TO TURN NORTHWESTWARD AROUND TAU 24 AS THE SUBTROPICAL RIDGE TO THE NORTH BUILDS IN. BY TAU 36, TS 07W AND TS 09W ARE EXPECTED TO MERGE, WITH TS 07W REMAINING AS THE DOMINANT CIRCULATION. AS TS 07W MOVES NORTHEASTWARD, THE NORTHEASTERLY VERTICAL WIND SHEAR SHOULD DECREASE AND ALLOW TS 07W TO INTENSIFY SLIGHTLY. TS LIONROCK IS EXPECTED TO REACH SOUTHEASTERN CHINA BY TAU 48 AND DISSIPATE AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND BY TAU 72. ANOTHER POSSIBLE SCENARIO IS THAT TS 09W DISSIPATES PRIOR TO MERGER WITH TS 07W. THE AVAILABLE NUMERICAL MODEL GUIDANCE DIFFER IN THE TIMING OF THE TURN NORTH AND NORTHWESTWARD WITH GFS AS THE EASTERN OUTLIER. THIS FORECAST TURNS TS 07W SLIGHTLY FASTER THAN MODEL CONSENSUS AND IS IN AGREEMENT WITH NOGAPS, ECMWF, AND GFDN.// NNNN