MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN) WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 15W (FIFTEEN), LOCATED APPROXIMATELY 96 NM EAST-NORTHEAST OF YAP, HAS TRACKED WESTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY (MSI) DEPICTS A SLIGHTLY LESS CONSOLIDATED LOW-LEVEL CIRCULATION CENTER (LLCC) THAN 6 HOURS AGO, WITH BROAD CONVECTION VISIBLE ALONG THE WESTERN AND SOUTHERN PERIPHERY. A 102111Z SSMIS IMAGE DEPICTS CONVECTIVE ACTIVITY ALONG THE EXTREME WESTERN EDGE OF THE SYSTEM. INITIAL POSITION IS BASED ON THE MSI LOOP WITH LOW CONFIDENCE AS THE MAIN AREAS OF CONVECTION HAVE BEEN SHEARED TO THE WEST OF THE APPARENT LLCC. UPPER LEVEL ANALYSIS INDICATES EQUATORWARD OUTFLOW AND MODERATE (15 TO 20 KTS) NORTHEASTERLY VERTICAL WIND SHEAR (VWS). INTENSITY IS MAINTAINED AT 25 KNOTS BASED ON CURRENT DVORAK INTENSITY ESTIMATES FROM ALL AGENCIES. 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 STR TO THE NORTHEAST CONTINUES TO INFLUENCE THE WEST TO WEST-NORTHWEST TRACK OF TD 15W THROUGH TAU 48. WHILE MODELS ARE IN AGREEMENT THAT THE STR BREAKS DOWN, THERE IS SIGNIFICANT DISAGREEMENT IN THE DEGREE OF THE WEAKNESS IN THE RIDGE. NAVGEM DEPICTS THE STR BREAKING DOWN FASTER AND THE SYSTEM TURNING TO THE NORTH INTO A SMALL BREAK IN THE RIDGE BEYOND TAU 48 AND THEN CONTINUING TO THE NORTHWEST. GFS AND ECMWF SOLUTIONS HAVE TD 15W SLOWING SLIGHTLY BY TAU 48 AND 72 DUE TO THE SMALL BREAK IN THE RIDGE AND THE WEAKENING STEERING ENVIRONMENT, BEFORE CONTINUING WESTWARD UNDER THE RE-BUILDING STR. THE INTENSITY OF THE SYSTEM IS EXPECTED TO INCREASE AT A STEADY RATE THROUGH TAU 72, WITH GOOD MODEL AGREEMENT, DUE TO HIGH SEA SURFACE TEMPERATURES AND A FAVORABLE UPPER-LEVEL ENVIRONMENT. C. BEYOND TAU 72, MODELS CONTINUE TO DIVERGE, WITH THE GFS AND ECMWF SOLUTIONS TAKING THE SYSTEM THROUGH NORTH CENTRAL LUZON AND THE NAVGEM MODEL FAVORING A TRACK TOWARDS SOUTHERN TAIWAN. AS SUCH, THE FORECAST TRACK IN THE LATER TAUS ALIGNS CLOSELY WITH THE CONSENSUS OF MODEL GUIDANCE, TRACKING INTO NORTHERN LUZON AFTER BY TAU 96. 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 DISPARITIES DEPICTED IN THE DIFFERENT MODELSâ STEERING ENVIRONMENTS AFTER TAU 48.// NNNN NNNN