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 279 NM EAST OF SAIPAN, HAS TRACKED NORTHWESTWARD AT 06 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY REVEALS DEEP CONVECTION TO THE SOUTH OF A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). A 141701Z SSMI 85 GHZ MICROWAVE IMAGE DEPICTS SHALLOW BANDING TO THE NORTH OF THE LLCC. BASED ON THOSE IMAGES, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. A 141127Z METOP-C ASCAT IMAGE AND A 141200Z METOP-B ASCAT IMAGE SHOWED A BROAD REGION OF 25-30 KT WINDS WRAPPING AROUND THE SOUTHERN HALF OF THE CIRCULATION. THE 25 KT INITIAL INTENSITY ALIGNS WITH THE ASCAT PASSES AND A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF T1.0 (25 KTS). STRONG (25-50 KT) VERTICAL WIND SHEAR (VWS) IS OFFSETTING EXCELLENT EQUATORWARD OUTFLOW AND WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURE (SST) TO MAKE THE ENVIRONMENT UNFAVORABLE FOR INTENSIFICATION. TD 17W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SHALLOW, NORTHWEST-TO-SOUTHEAST ORIENTED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST PHILOSOPHY. B. FOR THE DURATION OF THE FORECAST, TD 17W WILL TRACK NORTHWESTWARD ALONG THE PERIPHERY OF THE STR. THE UNFAVORABLE ENVIRONMENT IS EXPECTED TO KEEP INTENSITY TO 30 KTS OR LESS. THE INTENSITY FORECAST IS JUST BELOW THE INTENSITY CONSENSUS, OFFSETTING THE UNLIKELY HWRF PEAK OF 45 KTS AT TAU 24, BUT SLIGHTLY ABOVE THE BULK OF THE INTENSITY GUIDANCE. DISSIPATION WILL LIKELY OCCUR SOMETIME AFTER TAU 48, IF NOT SOONER, AS THE CURRENTLY UNDER CONTINUED UNFAVORABLE ENVIRONMENTAL CONDITIONS. NUMERICAL MODEL GUIDANCE IS IN EXCELLENT AGREEMENT THROUGH TAU 24. AFTER TAU 24, SPREAD INCREASES AS TWO MODEL SOLUTIONS DIVERGE SLIGHTLY FROM THE OTHERS (UKMET IS SLIGHTLY MORE POLEWARD AND THE 140000Z ECMWF ENSEMBLE MEAN IS SLIGHTLY MORE WESTWARD). THE JTWC TRACK FORECAST IS PLACED CLOSE TO CONSENSUS, NEAR THE BULK OF THE GUIDANCE, WITH FAIR CONFIDENCE.// NNNN NNNN