MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) WARNING NR 03// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 17W (SEVENTEEN), LOCATED APPROXIMATELY 651 NM SOUTHEAST OF IWO TO, JAPAN, HAS TRACKED NORTHWESTWARD AT 13 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY SHOWS A FULLY-EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) TRACKING NORTHWARD, PROVIDING HIGH CONFIDENCE IN THE INITIAL POSITION. A 142359Z METOP-C ASCAT IMAGE DISPLAYS AN AREA OF 30 KNOT WINDS NEAR THE LLCC, WHICH LENDS HIGH CONFIDENCE TO THE INITIAL INTENSITY OF 30 KNOTS. DESPITE STRONG EQUATORWARD OUTFLOW AND HIGH (30-31 CELSIUS) SEA SURFACE TEMPERTURE (SST), TD 17W REMAINS IN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED BY HIGH (25-40 KNOTS) VERTICAL WIND SHEAR (VWS). TD 17W CONTINUES TO TRACK AROUND THE SOUTHWESTERN PERIPHERY OF A SHALLOW, NORTH-TO-SOUTH ORIENTED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. FOR THE DURATION OF THE FORECAST, TD 17W WILL TRACK NORTHWESTWARD ALONG THE STR. THE ENVIRONMENT IS EXPECTED TO REMAIN UNFAVORABLE FOR FURTHER INTENSIFICATION AS VWS VALUES PERSIST AT 40-50 KNOTS, SHEARING THE SYSTEM UNTIL DISSIPATION AROUND TAU 48. WITH MINOR DIFFERENCES IN ALONG TRACK SPEED, NUMERICAL GUIDANCE IS IN FAIR AGREEMENT, PLACING FAIR CONFIDENCE IN THE JTWC TRACK FORECAST WHICH IS LAID CLOSE TO CONSENSUS.// NNNN NNNN