MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 17W (SEVENTEEN), LOCATED APPROXIMATELY 607 NM EAST-SOUTHEAST OF MISAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A COMPACT, CONSOLIDATING LOW-LEVEL CIRCULATION CENTER WITH PERSISTENT CENTRAL CONVECTION. A 102037Z SSMIS 91GHZ IMAGE SHOWS CURVED CONVECTIVE BANDING OVER THE SOUTH QUADRANT WRAPPING INTO THE EAST QUADRANT. A 102327Z ASCAT IMAGE SHOWS 25 TO 30 KNOT WINDS OVER THE SOUTH AND EAST QUADRANTS OF THE LLCC. THE CURRENT INTENSITY IS ASSESSED AT 30 KNOTS AND IS BASED ON DVORAK ESTIMATES RANGING FROM T1.5 (25 KNOTS) TO T2.0 (30 KNOTS) AND THE ASCAT DATA. THIS SYSTEM IS LOCATED UNDER AN UPPER-LEVEL RIDGE, AND IS LOCATED SOUTH OF A FRONTAL SYSTEM WITH NO EVIDENCE OF BAROCLINIC INTERACTION. SST VALUES ARE WARM (27 TO 28C) AND POLEWARD OUTFLOW IS FAVORABLE. TD 17W IS ACCELERATING NORTHEASTWARD ALONG THE NORTHWEST PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THIS PROGNOSTIC REASONING MESSAGE SETS THE FORECAST PHILOSOPHY. B. TD 17W IS FORECAST TO ACCELERATE AND TRACK POLEWARD OF THE STR WITHIN THE NEXT 12 HOURS, AND WILL TURN EASTWARD AS IT TRACKS WITHIN THE MIDLATITUDE WESTERLIES. TD 17W IS FORECAST TO UNDERGO EXTRA-TROPICAL TRANSITION (ETT) WITHIN THE NEXT 12 HOURS AND WILL COMPLETE ETT BY TAU 24 AS IT GAINS FRONTAL CHARACTERISTICS. TD 17W IS NOT EXPECTED TO INTENSIFY AND WILL REMAIN AT TROPICAL DEPRESSION STRENGTH THROUGH THE FORECAST PERIOD. DYNAMIC GUIDANCE IS LIMITED BUT GENERALLY SUPPORTS THE FORECAST TRACK WITH HIGH CONFIDENCE.// NNNN NNNN