MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN) WARNING NR 03// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 13W (THIRTEEN), LOCATED APPROXIMATELY 290 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 20 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION WITH FLARING DEEP CONVECTION ACROSS THE WESTERN SEMICIRCLE. A 262248Z SSMIS 37GHZ MICROWAVE IMAGE INDICATES FRAGMENTED BANDING WRAPPING INTO A BROAD LOW LEVEL CIRCULATION CENTER, THEREFORE, THERE IS POOR CONFIDENCE IN THE CURRENT POSITION. THE CURRENT INTENSITY IS ASSESSED AT 30 KNOTS BASED ON A MULTI-AGENCY DVORAK ESTIMATES OF T1.0-2.0 (25-35 KNOTS) AND A 270100Z ADT ESTIMATE OF 32 KNOTS. ENVIRONMENTAL ANALYSIS REVEALS A MARGINALLY FAVORABLE ENVIRONMENT WITH MODERATE TO STRONG (20-30) VERTICAL WIND SHEAR OFFSET BY MODERATELY FAVORABLE DIFFLUENCE ALOFT AND WARM SST (28-30C). TD 13W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. IN THE NEAR TERM, TD 13W WILL TRACK WEST-NORTHWESTWARD MAKING LANDFALL OVER EASTERN LUZON NEAR TAU 12. DUE TO THE MARGINALLY FAVORABLE ENVIRONMENT, THE SYSTEM IS EXPECTED TO INCREASE TO MINIMAL TROPICAL STORM STRENGTH (35 KNOTS) AT TAU 12 BEFORE LANDFALL. TD 13W IS EXPECTED TO MAINTAIN INTENSITY AS IT CROSSES LUZON DUE TO LAND INTERACTION EFFECTS AND THEN IS EXPECTED TO CONTINUE TO INTENSIFY TO 50 KNOTS BY TAU 72. THERE IS HIGH UNCERTAINTY IN THE INTENSITY AS IT REDEVELOPS WEST OF LUZON DUE TO THE SUSTAINED MODERATE SHEAR, MODERATE UPPER LEVEL DIVERGENCE AND BROAD NATURE OF THE SYSTEM. THE SYSTEM IS EXPECTED TO CONTINUE TRACKING WESTWARD TO WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR POSITIONED TO THE NORTH THROUGH TAU 72. C. AFTER TAU 72, A DEEP SHORTWAVE TROUGH IS FORECAST TO DIG OVER EASTERN CHINA WHICH WILL WEAKEN THE STR AND ALLOW THE SYSTEM TO TURN MORE POLEWARD TOWARD HAINAN ISLAND. THE SYSTEM IS EXPECTED TO MAINTAIN INTENSITY THROUGH TAU 96 AS IT PASSES ALONG THE SOUTHERN EDGE OF HAINAN. AFTER TAU 96, TD 13W SHOULD STEER NORTHWESTWARD AS IT TRANSITIONS TO THE WESTERN STR WITH SLIGHT WEAKENING AS IT BEGINS TO INTERACT WITH VIETNAM. THE DYNAMIC MODEL GUIDANCE IS IN FAIR AGREEMENT WITH TWO OUTLIERS (NAVGEM AND GFS), THEREFORE, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.// NNNN NNNN