MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN) WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 15W (FIFTEEN), LOCATED APPROXIMATELY 179 NM EAST OF YAP, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A CONSOLIDATED LOW-LEVEL CIRCULATION CENTER WITH VIGOROUS CONVECTION ALONG THE WESTERN PERIPHERY. A 101642Z AMSU-B IMAGE FURTHER SHOWS GOOD CONVECTIVE BANDING ALONG THE NORTHERN AND WESTERN PERIPHERY OF THE SYSTEM. LOCAL OBSERVATIONS FROM YAP INDICATE A DROP IN PRESSURE OF 02 MB OVER THE PAST 24 HOURS. UPPER LEVEL ANALYSIS INDICATES EQUATORWARD OUTFLOW AND MODERATE (20 TO 30 KTS) OF VERTICAL WIND SHEAR (VWS). INTENSITY IS BASED ON DVORAK INTENSITY ESTIMATES WITH THE MAJORITY OF AGENCIES AGREEING WITH A MAXIMUM WIND SPEED OF 25 KNOTS. TD 15W IS CURRENTLY TRACKING WESTWARD UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST OF THE SYSTEM. 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST PHILOSOPHY. B. THE MAIN STEERING INFLUENCE OF TD 15W THROUGH TAU 72 IS THE STR TO THE NORTHEAST. AS THE MAIN STR BREAKS DOWN AND TRAVERSES SLIGHTLY TO THE EAST, EXPECT THE TD 15W TO SLOW SLIGHTLY IN THE LATER TAUS BEFORE CONTINUING WESTWARD UNDER THE RE-BUILDING STR. AN ALTERNATE SCENARIO, FAVORED BY THE NAVGEM SOLUTION, HAS THE STR RIDGE TO THE EAST OF THE SYSTEM BREAKING DOWN FASTER AND 15W TURNING TO THE NORTH BETWEEN A SMALL BREAK IN THE RIDGE BY TAU 48. WHILE ALL MODEL TRACKERS ARE IN GOOD AGREEMENT THROUGH 18Z ON THE 12TH, THERE IS SOME DISAGREEMENT BEYOND THAT POINT. WITH REGARD TO INTENSITY, GOOD SEA SURFACE TEMPERATURES AND FAVORABLE UPPER-LEVEL ENVIRONMENT SHOULD ALLOW THE SYSTEM TO INTENSIFY AT AN AVERAGE RATE THOUGH TAU 72. C. IN THE EXTENDED FORECAST THE MODEL SOLUTIONS BEGINS TO FURTHER DIVIDE, WITH THE GFS TRACKING INTO LUZON AND NAVGEM BEGINNING A RECURVE SCENARIO BETWEEN A WEAKNESS IN THE STR. THE FORECAST TRACK IN THE LATER TAUS ALIGNS CLOSELY WITH THE CONSENSUS OF MODEL GUIDANCE, TRACKING INTO NORTHERN LUZON BY TAU 108. LAND INTERACTION DURING THIS TIMEFRAME WILL IMPEDE FURTHER INTENSIFICATION DESPITE FORECASTED GOOD EQUATOR OUTFLOW AND AVERAGE VWS. THE OVERALL CONFIDENCE IN JTWC TRACK IS LOW DUE TO A SLIGHT DISPARITY IN MODELS AFTER TAU 48.// NNNN NNNN