WDPN31 PGTW 090900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (ETAU) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 24W (ETAU), LOCATED APPROXIMATELY 293 NM EAST- SOUTHEAST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS RELATIVELY SYMMETRIC DEEP CONVECTION FLARING OVER THE ASSESSED CENTER, WITH SHALLOWER CONVECTIVE BANDING WRAPPING INTO THE NORTHWESTERN QUADRANT OF THE OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). A 090544Z ATMS 88GHZ MICROWAVE IMAGE REVEALS SHALLOW BANDING IN THE SOUTHEASTERN QUADRANT, WITH AN ELONGATED BAND OF DEEPER BANDING IN THE NORTHWESTERN QUADRANT AND LENDS HIGH CONFIDENCE TO THE INITIAL POSITION BASED ON A NASCENT MICROWAVE EYE FEATURE. THE INITIAL INTENSITY IS ASSESSED AT 35 KTS WITH MODERATE CONFIDENCE AND IS HEDGED SLIGHTLY HIGHER THAN MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T2.5 (35 KNOTS) FROM PGTW/RJTD IN LIGHT OF A DVORAK ESTIMATE OF T3.0 (40 KNOTS) FROM BOTH KNES AND VIA THE ADVANCED DVORAK TECHNIQUE (ADT). UPPER-LEVEL ANALYSIS INDICATES A GENERALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (15-20 KNOTS) EASTERLY VERTICAL WIND SHEAR AND SINGLE CHANNEL OUTFLOW, WHICH IS OFFSETTING WEAKLY SUPPORTIVE SST VALUES BETWEEN 27C TO 28C. TS 24W CONTINUES TRACKING ALONG THE SOUTHERN PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 24W IS FORECAST TO CONTINUE TRACKING WESTWARD THROUGH THE ENTIRE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE AFOREMENTIONED STR THROUGH, MAKING LANDFALL OVER EASTERN VIETNAM NEAR TAU 18. TS 24W HAS LIKELY REACHED PEAK INTENSITY. AS THE SYSTEM CONTINUES TRACKING WEST, SSTS STEADILY DECREASE AS IT APPROACHES THE COAST OF VIETNAM WHILE VWS WILL STEADILY INCREASE THROUGH TAU 24. AFTER LANDFALL, THE SYSTEM WILL TRACK INLAND AND DISSIPATE OVER CENTRAL CAMBODIA BY TAU 48. NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A SPREAD OF 50NM AT LANDFALL WITH JGSM BEING A EQUATORWARD OUTLIER, THE REMAINDER OF THE GUIDANCE BEING EXTREMELY TIGHTLY PACKED (19NM SPREAD) AT LANDFALL, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN