WDPN33 PGTW 100300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W WARNING NR 09// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 10W (ETAU) HAS MAINTAINED PERSISTENT CONVECTION OVER THE LOW LEVEL CIRCULATION CENTER (LLCC) DURING THE PAST 12 HOURS; EVIDENT IN ANIMATED INFRARED AND MULTISPECTRAL IMAGERY. IN THE PAST 03 HOURS THE ANIMATED IMAGERY SHOWS A STRONG SURGE OF CONVECTION MOVING TO THE SOUTHWEST, IN THE UPPER LEVELS ASSOCIATED WITH AN EXTENSION OF A POINT SOURCE ANTI-CYCLONE LOCATED TO THE WEST OF TS 10W. INCREASED CONVECTION HAS ALSO BEEN DEVELOPING ON THE NORTHEASTERN QUADRANT AS TS 10W HAS MOVED CLOSER TO THE BAROCLINIC ZONE OVER SOUTHERN JAPAN. THE UPPER LEVEL JET ASSOCIATED WITH THE BAROCLINIC ZONE HAS BEEN HELPING TO IMPROVE THE POLEWARD OUTFLOW OF TS 10W FOR THE PAST 12 HOURS. TS 10W HAS TRACKED ON A NORTHWARD TRACK OVER THE PAST 12 HOURS AROUND THE WESTERN PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) LOCATED TO THE EAST OF TS 10W. BASED ON THE IMPROVED CONVECTIVE SIGNATURE OF TS 10W AND INTENSITY ESTIMATES FROM PGTW INDICATING AT LEAST 30 KNOTS, THE INTENSITY HAS BEEN INCREASED TO 35 KNOTS OVER THE PAST 12 HOURS. 3. FORECAST REASONING A. THE FORECAST PHILOSOPHY HAS NOT SIGNIFICANTLY CHANGED SINCE THE LAST PROGNOSTIC REASONING BULLETIN. B. TS 10W IS FORECAST TO INTENSIFY SLOWLY AS IT BEGINS TO RECURVE AROUND THE WESTERN EXTENT OF THE STR WITHIN THE NEXT 12 HOURS. INCREASED INTERACTION WITH THE BAROCLINIC ZONE OVER JAPAN BEYOND TAU 12 WILL INCREASE TRACK SPEED TO THE EAST-NORTHEAST AROUND THE NORTHWESTERN PERIPHERY OF THE STR, OVER THE RELATIVELY WARMER WATERS OF THE KUROSHIO CURRENT. BETWEEN TAU 36 AND TAU 48 THE BAROCLINIC MID-LATITUDE FLOW WILL BEGIN TO ABSORB TS 10W, CAUSING AN INCREASE IN TRACK SPEED TO THE NORTHEAST. EXTRA-TROPICAL (ET) TRANSITION IS ANTICIPATED TO BEGIN AROUND TAU 36 WITH TS 10W BEING FULLY ET BY TAU 48. TRACK IS PRESENTED WITH HIGH CONFIDENCE THROUGH TAU 48 AND IS BASED ON AN EXCELLENT GROUPING OF OBJECTIVE AIDS. FORECAST TEAM: BRAVO// NNNN