MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KHANUN) WARNING NR 05// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 24W (KHANUN), LOCATED APPROXIMATELY 621 NM EAST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A LOW- LEVEL CIRCULATION CENTER (LLCC) WHICH CONTINUES TO CONSOLIDATE. EXTENSIVE CONVECTIVE BANDING IN THE LUZON STRAIT CONTINUES TO WRAP INTO THE LLCC. A 130656Z GMI 37GHZ COMPOSITE IMAGE SHOWS THE SYSTEM IS CONTINUING TO IMPROVE IN OVERALL STRUCTURE WITH THE LLCC LOCATED TO THE WEST OF LUZON. THE INITIAL INTENSITY IS ASSESSED AT 45 KNOTS BASED ON A DVORAK ESTIMATE OF T3.0 (45 KNOTS) FROM PGTW. UPPER-LEVEL ANALYSIS DEPICTS A GENERALLY FAVORABLE ENVIRONMENT WITH MODERATE VERTICAL WIND SHEAR (20 TO 25 KNOTS). POLEWARD AND EQUATORWARD OUTFLOW BOTH REMAIN EXCELLENT AND SEA SURFACE TEMPERATURES REMAIN WARM (29-30 CELSIUS). TS 24W IS UNDER THE STEERING INFLUENCE OF THE EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE 34-KNOT WIND RADII REMAIN EXTENSIVE THROUGH TAU 48 DUE TO THE INTERACTION WITH THE STRONG NORTHEASTERLY SURGE FLOW. B. TS 24W WILL TRACK WEST-NORTHWESTWARD AS IT REMAINS ON THE SOUTHWESTERN PERIPHERY OF THE DEEP-LAYERED STR. THE STR WILL REMAIN THE PRIMARY STEERING MECHANISM THROUGHOUT THE FORECAST. HOWEVER, A SLIGHT WEAKENING IN THE STR WILL ALLOW THE TRACK OF TS 24W TO BECOME WEST-NORTHWESTWARD AS IT TRANSITS THE SOUTH CHINA SEA. TS 24W WILL ALSO INCREASE IN INTENSITY AS IT TRACKS ACROSS WARM SEA SURFACE TEMPERATURES WITH FAVORABLE UPPER-LEVEL CONDITIONS. BY TAU 36 THE INTENSITY WILL INCREASE TO 75 KNOTS AS TS 24W APPROACHES HAINAN ISLAND. NUMERICAL MODEL GUIDANCE IS GENERALLY IN GOOD AGREEMENT WITH A WEST-NORTHWESTWARD TRACK. HOWEVER, THERE IS NOW A GREATER SPREAD IN THE MODEL TRACK FORECASTS WHEN COMPARED TO PREVIOUS MODEL RUNS. C. IN THE EXTENDED PERIOD, TS 24W WILL TRACK WESTWARD AND WILL MAKE A SECOND LANDFALL IN NORTHERN VIETNAM NEAR TAU 84 AND WILL WEAKEN RAPIDLY AS IT MOVES INLAND. OVERALL, DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT UNTIL AFTER TAU 96 WHERE SEVERAL MODELS ERRONEOUSLY SHOW THE REMNANTS OF TS 24W TURNING SHARPLY SOUTHWARD. THE STR LOCATED TO THE NORTH IS EXPECTED TO REMAIN STRONG ENOUGH DURING THIS TIME PERIOD TO KEEP THE TRACK MORE WESTWARD. OVERALL THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN