MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (KAMMURI) WARNING NR 10// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 17W (KAMMURI), LOCATED APPROXIMATELY 200 NM EAST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY CONTINUES TO DEPICT A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH SPIRAL BANDING OVER 600NM IN DIAMETER WRAPPING INTO THE LLCC. A 261721Z SSMI AND 261703Z AMSU-B IMAGE SHOW FRAGMENTED BANDING WARPING INTO A VERY LARGE CENTROID FEATURE, RESEMBLING A LARGE MONSOON DEPRESSION. THE CURRENT POSITION IS BASED ON THE EIR ANIMATION AND AFOREMENTIONED MICROWAVE IMAGERY WITH LOW CONFIDENCE DUE TO THE BROAD NATURE OF THE CENTER. THE INITIAL INTENSITY REMAINS AT 55 KNOTS BASED ON AN OVERALL ASSESSMENT OF DVORAK CURRENT INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW (10 TO 15 KNOT) VERTICAL WIND SHEAR (VWS) AND RADIAL OUTFLOW. TS 17W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE EAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. THE STR WILL REMAIN THE DOMINANT STEERING MECHANISM FOR TS 17W THROUGH TAU 48. TS KAMMURI IS FORECAST TO TURN POLEWARD AFTER TAU 24 AS IT CONTINUES TO ROUND THE STR AXIS AND BEGINS TO RE-CURVE AHEAD OF AN APPROACHING MID-LATITUDE SHORTWAVE TROUGH. IN ADDITION TO THE WARM SEA SURFACE TEMPERATURES, A FAVORABLE UPPER-LEVEL ENVIRONMENT IS EXPECTED TO PERSIST ALLOWING TS 17W TO FURTHER CONSOLIDATE AND REACH TYPHOON STRENGTH OVER THE NEXT 24 HOURS. COMPARING THE LATEST FSU GFS CYCLONE PHASE SPACE DIAGRAM AND OTHER TRACK DATA, EXPECT KAMMURI TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 48, AS IT IS FORECASTED TO BE ABOVE THE RIDGE ACCESS AND BECOME EMBEDDED IN THE MID-LATITUDE WESTERLIES WITH THE COMPLETION OF ETT BY TAU 72. AVAILABLE MODEL GUIDANCE IS OVERALL IN FAIR AGREEMENT; HOWEVER, THE OVERALL CONFIDENCE IN JTWC FORECAST TRACK IS LOW DUE TO THE UNCERTAINTY IN ITS INITIAL POSITION.// NNNN NNNN