WDPN31 PGTW 220300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (KROVANH) WARNING NR 009// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 26W (KROVANH), LOCATED APPROXIMATELY 308 NM SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED SOUTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS LOW-LEVEL CLOUD LINES WRAPPING INTO A PARTIALLY-EXPOSED, COMPACT LOW-LEVEL CIRCULATION CENTER WITH DEEP CONVECTION DISPLACED TO THE NORTH. A 212354Z SCATTEROMETER IMAGE INDICATES A DEFINED CIRCULATION WITH 30-35 KNOT WINDS TO THE WEST AND NORTH AND WEAKER WINDS ELSEWHERE, WHICH SUPPORTS THE INITIAL INTENSITY ASSESSMENT OF 30 KNOTS. SURFACE OBSERVATIONS FROM HUYEN TRAN (48919; LOCATION 8.0N 110.6E) INDICATE NNW WINDS AT 17 KNOTS (21/18Z) VEERING TO NE AT 19 KNOTS (22/00Z) AS THE CENTER PASSED JUST SOUTH. HOWEVER, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION BASED ON THE WEAK NATURE OF THE SYSTEM. UPPER- LEVEL ANALYSIS REVEALS A MARGINAL ENVIRONMENT WITH MODERATE (15-20 KNOTS) VERTICAL WIND SHEAR OFFSET BY STRONG POLEWARD OUTFLOW. SST VALUES (27-28C) REMAIN CONDUCIVE. THE SYSTEM IS TRACKING WEST- SOUTHWESTWARD ALONG THE SOUTHEAST PERIPHERY OF A LOW-LEVEL SUBTROPICAL RIDGE POSITIONED TO THE NORTHWEST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 26W IS EXPECTED TO TRACK WEST-SOUTHWESTWARD TO WESTWARD ALONG THE SOUTHERN FLANK OF THE LOW-LEVEL STR THROUGH TAU 24. THE SYSTEM IS FORECAST TO WEAKEN STEADILY AS IT TRACKS AWAY FROM THE STRONG SURGE FLOW OVER COOLER WATER (25-26C) WITH WEAK UPPER-LEVEL DIVERGENCE. THE SYSTEM IS FORECAST TO DISSIPATE SOUTH OF VIETNAM BY TAU 24. THE BULK OF THE NUMERICAL MODEL GUIDANCE SUPPORTS THE JTWC FORECAST TRACK WITH MODERATE CONFIDENCE, HOWEVER, THERE IS SOME UNCERTAINTY IN THE INITIAL POSITION.// NNNN