MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (NOUL) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 13W (NOUL), LOCATED APPROXIMATELY 272 NM EAST OF DA NANG, VIETNAM, HAS TRACKED NORTHWESTWARD AT 17 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY-EXPOSED, WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC), SUPPORTING THE INITIAL POSITION WITH GOOD CONFIDENCE. THE MSI SHOWS LIMITED DEEP CONVECTION OVER THE WESTERN QUADRANT OF THE LLCC. A 170539Z ATMS 88.2 GHZ MICROWAVE IMAGE REVEALS LIMITED DEEP CONVECTIVE BANDING OFFSET FROM THE LLCC OVER THE WESTERN SEMICIRCLE. THE INITIAL INTENSITY REMAINS ASSESSED AT 45 KTS BASED ON THE HIGHER END OF DVORAK ESTIMATES OF T2.5-3.0 (35-45 KTS, PGTW/RJTD). FURTHERMORE, THE INITIAL INTENSITY IS BASED ON A 170610Z ADVANCED DVORAK TECHNIQUE ESTIMATE OF T3.4 (ABOUT 55 KTS) AND A 170136Z SATCON ESTIMATE OF 48 KTS. ENVIRONMENTAL ANALYSIS INDICATES PERSISTENT 20-25 KT NORTHEASTERLY VERTICAL WIND SHEAR (VWS) BEING OFFSET BY EQUATORWARD OUTFLOW, WARM SST VALUES (30-31 CELSIUS), AND HIGH OCEAN HEAT CONTENT VALUES, MAINTAINING AN OVERALL MARGINAL ENVIRONMENT FOR DEVELOPMENT. POLEWARD OUTFLOW IS BEING RESTRICTED BY CONVERGENT FLOW TO THE NORTH. TS 13W IS TRACKING ALONG THE SOUTHEASTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. ALL WIND RADII HAVE BEEN UPDATED BASED ON RECENT ASCAT DATA. B. FOR THE REMAINDER OF THE FORECAST PERIOD, TS 13W WILL TRACK WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR. THE WARM WATERS OF THE SOUTH CHINA SEA WILL ENABLE THE SYSTEM TO SLIGHTLY INTENSITFY IN THE NEAR TERM DESPITE CONTINUED MODERATE TO HIGH (20- 30 KT) VWS. THIS INTENSIFICATION WILL BE FURTHER SUPPORTED BY CONTINUED EQUATORWARD OUTFLOW, REACHING A PEAK INTENSITY OF 50 KTS BY TAU 12. THE SYSTEM IS EXPECTED TO MAINTAIN THIS INTENSITY UNTIL IT MAKES LANDFALL NEAR HUE, VIETNAM JUST AFTER TAU 24. FOLLOWING LANDFALL, THE MOUNTAINOUS TERRAIN AND CONTINUED STRONG VWS WILL STEADILY WEAKEN THE SYSTEM AND FULL DISSIPATION OVER LAND IS ANTICIPATED BY TAU 48 AS TS 13W TRACKS DEEPER INTO SOUTHEAST ASIA. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A SPREAD OF 107 NM AT TAU 24. THE GFS AND JGSM SOLUTIONS ACT AS THE SOUTHERLY AND NORTHERLY OUTLIERS, RESPECTIVELY. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN