MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT) WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 28W (TWENTYEIGHT), LOCATED APPROXIMATELY 139 NM SOUTH-SOUTHEAST OF ENEWETAK, HAS TRACKED WESTWARD AT 17 KNOTS OVER THE PAST SIX HOURS. ANIMATED HIGH RESOLUTION VISIBLE SATELLITE IMAGERY SHOWS THE SYSTEM HAS SLOWLY CONSOLIDATED AS FORMATIVE BANDS HAVE BEGUN TO WRAP INTO A WEAKLY DEFINED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS BASED ON ANALYSIS OF THE ABOVE WITH POOR CONFIDENCE. THE INITIAL INTENSITY OF 30 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY DVORAK ESTIMATES BETWEEN T1.5 AND T2.0 (30-35 KNOTS) AND IS SUPPORTED BY A 101910Z WINDSAT SCATTEROMETER BULLSEYE SHOWING A BROAD AREA OF 25-30 KNOT WINDS NEARLY SURROUNDING THE LLCC. HIGHER WINDS ARE INDICATED IN THE WINDSAT DATA, BUT ANALYSIS INDICATES THESE ARE UNREPRESENTATIVE OF THE ACTUAL WIND FIELD. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF LOW TO MODERATE (10-15 KNOTS) VERTICAL WIND SHEAR (VWS) AND WEAKLY DIVERGENT EQUATORWARD OUTFLOW. THE SYSTEM IS TRACKING WESTWARD WITH THE GRADIENT WIND FLOW SOUTH OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE AND SETS THE FORECAST PHILOSOPHY ON THIS SYSTEM. B. TD 28W IS EXPECTED TO TRACK WESTWARD UNDER THE INFLUENCE OF THE STR TO THE NORTH THROUGH THE FIRST 72 HOURS. THE UPPER LEVEL ENVIRONMENT WILL REMAIN MARGINALLY FAVORABLE WITH LOW TO MODERATE VWS, WARM SEA SURFACE TEMPERATURES AND WEAK WESTERLY OUTFLOW, WHICH WILL PROMOTE SLOW INTENSIFICATION THROUGH TAU 72. C. IN THE EXTENDED TAU'S, THE STR WILL REMAIN IN PLACE AS THE DOMINANT STEERING MECHANISM AND THE SYSTEM WILL REMAIN ON A GENERALLY WESTWARD TRACK. MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST, BRINGING TD 26W TO 60 KNOTS BY END OF FORECAST. THE AVAILABLE NUMERICAL GUIDANCE IS IN TIGHT AGREEMENT THROUGH THE FORECAST PERIOD AND THERE IS HIGH CONFIDENCE IN THE INITIAL JTWC TRACK FORECAST.// NNNN NNNN