WDPN31 PGTW 201500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (SAUDEL) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 19W (SAUDEL), LOCATED APPROXIMATELY 104 NM NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 09 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED SATELLITE IMAGERY REVEALS DEEP CONVECTION OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC) EAST OF LUZON. A 201046Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICTS CONVECTIVE BANDING WRAPPING IN FROM THE NORTH, PLACING GOOD CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS SET AT 45 KTS HEDGED BETWEEN DVORAK CURRENT INTENSITY ESTIMATES OF T2.5 (35 KT) BY KNES/RJTD AND T3.5 (55 KTS) BY PGTW BASED ON A 201326Z ASCAT- B IMAGE REVEALING 40-45 KT WINDS NEAR THE LLCC JUST OFF THE COAST OF LUZON. NEAR-RADIAL UPPER LEVEL OUTFLOW, LOW (10-15 KT) VERTICAL WIND SHEAR (VWS), AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST) CONTRIBUTE TO AN OVERALL FAVORABLE ENVIRONMENT FOR CONTINUED DEVELOPMENT. TS 19W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) EXTENSION POSITIONED TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 19W WILL CONTINUE TO TRACK GENERALLY WESTWARD UNDER THE STEERING INFLUENCE OF THE STR THROUGH TAU 72. HOWEVER, THE SYSTEM IS EXPECTED TO SLOW FROM TAU 36 TO TAU 72 AS THE STR TEMPORARILY WEAKENS DUE TO THE APPROACH OF A MIDLATITUDE SHORTWAVE TROUGH WHICH IS EXPECTED TO DIG OVER SOUTHEAST CHINA. DURING THIS TIME, NUMERICAL MODEL GUIDANCE INDICATES A SHORT-TERM NORTHWESTWARD TRACK DUE TO THE LACK OF STEERING GUIDANCE. NAVGEM AND ECMWF MODEL SOLUTIONS MAINTAIN A MORE AGGRESSIVE NORTH-NORTHWESTWARD TRACK SOLUTIONS AFTER TAU 24, TRACKING TS 19W FURTHER NORTH THAN THE CURRENT JTWC TRACK FORECAST. HOWEVER, THERE IS FAIR CONFIDENCE IN THE JTWC TRACK FORECAST AS IT IS POSITIONED WITH THE MAJORITY OF THE MODEL GUIDANCE AND NEAR THE MULTI-MODEL CONSENSUS. THE SYSTEM IS EXPECTED TO MAINTAIN ITS INTENSITY AS IT MAKES LANDFALL IN LUZON AND THEN INTENSIFY AS IT REEMERGES OVER THE SOUTH CHINA SEA NEAR TAU 12. AFTERWARDS, TS 19W SHOULD STEADILY INTENSIFY TO A PEAK OF 60 KTS BY TAU 48 UNDER CONTINUED FAVORABLE CONDITIONS. AS THE AFOREMENTIONED SHORTWAVE TROUGH PROPAGATES EASTWARD, THE STR WILL REBUILD TO THE NORTH, ALLOWING TS 19W TO ACCELERATE WESTWARD ALONG ITS SOUTHERN PERIPHERY. C. IN THE EXTENDED FORECAST, THE SYSTEM WILL MAINTAIN INTENSITY UNTIL IT BEGINS TO INTERACT WITH HAINAN ISLAND AROUND TAU 96. THIS INTERACTION INITIATE THE SLOW WEAKENING OF TS 19W AS IT APPROACHES THE COAST OF VIETNAM. DUE TO THE COMPLEX STEERING ENVIRONMENT AND DYNAMIC SYNOPTIC PATTERN, THERE IS MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN