MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (FENGSHEN) WARNING NR 008// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 26W (FENGSHEN), LOCATED APPROXIMATELY 620NM EAST-NORTHEAST OF WFO GUAM, HAS TRACKED WEST AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS PERSISTENT DEEP CONVECTION SHEARED TO THE SOUTHWEST OF THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE DEFINED FEATURE IN THE 130609Z SSMIS 89GHZ COLORIZED MICROWAVE IMAGE. THE INITIAL INTENSITY OF 45KTS IS BASED ON MULTI-AGENCY DVORAK INTENSITY ESTIMATES OF T2.5-3.0 (42-45 KNOTS). THE SYSTEM IS, OVERALL, IN A FAVORABLE AREA FOR FURTHER DEVELOPMENT WITH WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES, LOW (10-15 KNOT) VERTICAL WIND SHEAR (VWS) AND FAIR EQUATORWARD OUTFLOW DISPLACED TO THE SOUTH OF THE LLCC. THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 26W WILL CONTINUE ON ITS CURRENT TRACK SOUTHWEST OF THE STR THROUGH TAU 24 BEFORE IT TURNS POLEWARD AROUND TAU 48 AS IT ROUNDS THE WESTERN EDGE OF THE STR AXIS. THE OVERALL FAVORABLE ENVIRONMENT WILL PROMOTE GRADUAL INTENSIFICATION TO A PEAK 80 KNOTS BY TAU 72. THERE IS GOOD CONFIDENCE IN THE JTWC TRACK FORECAST AS MODEL GUIDANCE HAS IMPROVED WITH A SPREAD OF 100 NM AT TAU 48. C. AFTER TAU 72, TS 26W WILL TURN MORE EAST-NORTHEASTWARD AND WILL RAPIDLY WEAKEN AS IT INTERACTS WITH AN APPROACHING MIDLATITUDE TROUGH AND UNDERGOES STRONG VWS. THE SYSTEM IS EXPECTED TO BEGIN EXTRA- TROPICAL TRANSITION BY TAU 72. HOWEVER, THERE IS SOME UNCERTAINTY IN THE TRACK AT TAU 96 AS RIDING BUILDS IN TO THE WEST OF TC 26W. BY TAU 120, THE SYSTEM WILL BE REDUCED TO 30 KNOTS AND IS EXPECTED TO COMPLETE EXTRA-TROPICAL TRANSITION. DUE TO THE COMPLEX, EVOLVING STEERING PATTERN, THERE IS LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN