WDPN31 PGTW 100300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (ETAU) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 24W (ETAU), LOCATED APPROXIMATELY 240 NM SOUTH-SOUTHEAST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CENTRAL DENSE OVERCAST OBSCURING A LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE POSITION OF THE LOW LEVEL BANDING IN THE MSI LOOP AS WELL AS THE LOW LEVEL FEATURES PRESENT IN A 092340Z AMSU 89 GHZ IMAGE. THE INITIAL INTENSITY IS ASSESSED AT 30 KTS WITH FAIR CONFIDENCE BASED ON MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 (30 KTS, PGTW) AND T2.5 (35 KTS, RJTD). TD ETAU IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. ENVIRONMENTAL ANALYSIS REVEALS A MARGINAL ENVIRONMENT WITH LOW (10-15 KTS) VERTICAL WIND SHEAR AND COOL (< 26 CELSIUS) SEA SURFACE TEMPERATURES. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 24W IS FORECAST TO TRACK GENERALLY WESTWARD THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM WILL MAKE LANDFALL ALONG THE SOUTH-CENTRAL VIETNAM COAST SLIGHTLY BEFORE TAU 12 AND BEGIN TO DISSIPATE OVER LAND DUE TO CONTINUED MODERATE TO HIGH VWS AND INTERACTION WITH THE UNDERLYING TERRAIN. AS THE SYSTEM CENTER MOVES FURTHER INLAND, IT WILL CONTINUE TO WEAKEN AND COMPLETE DISSIPATION OVER LAND BY TAU 36. NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A SPREAD OF 30 NM AT LANDFALL. THIS SPREAD IN SOLUTIONS INCREASES THEREAFTER AS THE VARIOUS MODELS LOSE THE VORTEX SIGNATURE DUE TO THE DECAY OF THE SYSTEM OVER LAND. THIS TIGHT AGREEMENT IN MODEL TRACK GUIDANCE LENDS OVERALL HIGH CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS LAID ON THE MULTI- MODEL CONSENSUS.// NNNN