MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (PHANFONE) WARNING NR 027// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 30W (PHANFONE), LOCATED APPROXIMATELY 336 NM EAST-SOUTHEAST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 13 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH A SMALL CONVECTIVE CELL DISPLACED TO THE NORTHEAST. DUE TO THE FULLY EXPOSED NATURE OF THE LLCC, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY OF 30 KTS IS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 (30 KTS) BY PGTW AND RCTP, SUPPORTED BY A 280224Z METOP-C ASCAT BULLSEYE PASS DEPICTING A SMALL REGION OF 30-35 KT WINDS OT THE NORTHWEST. TD 30W MAINTAINS A GOOD POLEWARD OUTFLOW CHANNEL. HOWEVER, THIS IS OFFSET BY HIGH (30- 40 KTS) VERTICAL WIND SHEAR (VWS) AND COOL (25-26 CELSIUS) SEA SURFACE TEMPERATURES (SST) WHICH CREATE AN UNFAVORABLE ENVIRONMENT FOR THE SYSTEM. TD 30W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) AT 850 MB. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 30W WILL CONTINUE TO TRACK WESTWARD AND DISSIPATE BY TAU 24 AS THE ENVIRONMENT BECOMES LESS FAVORABLE DUE TO INCREASING VWS AND SST COOLING BELOW 25 CELSIUS. NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH TAU 12 AND THEN BEGIN TO SLOWLY DIVERGE THEREAFTER. THE UKMET ENSEMBLE AND GFS ENSEMBLE DEPICT A NORTHWESTWARD TRACK WHILE NAVGEM HAS A SOUTHWESTWARD SOLUTION. THESE DIFFERENCES ARE ATTRIBUTED TO THE MODEL VARIATIONS IN THE 850-700 MB FLOW WHICH IS MAINTAINED AS THE STEERING MECHANISM FOR TD 30W AS IT WEAKENS. THEREFORE, THE JTWC TRACK FORECAST HAS BEEN PLACED NEAR THE MULTI- MODEL CONSENSUS, LENDING FAIR CONFIDENCE TO THE FORECAST TRACK.// NNNN NNNN