WDPN33 PGTW 140300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (BEBINCA) WARNING NR 07// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 20W (BEBINCA), LOCATED APPROXIMATELY 87 NM SOUTH-SOUTHWEST OF HONG KONG, HAS TRACKED NORTH-NORTHEASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTI-SPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION SHEARED TO THE WEST. A 132240Z SSMIS 91 GHZ PASS IS CONSISTENT WITH THE MSI. THE INITIAL POSITION IS BASED ON THE PGTW FIX AND NOTED SSMIS CENTER. THE INITIAL INTENSITY IS ASSESSED AT 40 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF T2.5 (35 KNOTS) FROM PGTW, AND HEDGED SLIGHTLY HIGHER BASED ON RECENT SCATTEROMETRY INDICATING 40 KNOTS. ENVIRONMENTAL ANALYSIS INDICATES THAT THE SYSTEM LIES IN AN AREA OF STRONG (30 TO 35 KNOTS) EASTERLY VWS, WITH MARGINAL OUTFLOW. THE STEERING FLOW IS STARTING TO BECOME MORE DEFINED AS A STEERING RIDGE (STR) TO THE NORTH BUILDS. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE, HOWEVER, THE TRACK HAS BEEN SHIFTED NORTHWARD BASED ON THE LATEST ANALYSIS OF CURRENT TRACK MOTION. B. TS 20W IS FORECAST TO SLOWLY TRACK NORTHWARD TOWARD HONG KONG AND TURN BACK TO THE WEST AFTER TAU 12 UNDER THE STEERING FLOW OF THE STR. THE INTENSITY SHOULD REMAIN FAIRLY CONSTANT UNTIL LANDFALL OCCURS, AFTER WHICH A GRADUAL WEAKENING TREND WILL BEGIN. AFTER TAU 48, THE BUILDING STR MAY DEFLECT THE TRACK SOUTHWARD BACK OVER THE SOUTH CHINA SEA, ALLOWING FOR SLIGHT INTENSIFICATION BEFORE MAKING ANOTHER LANDFALL OVER VIETNAM. C. BEYOND TAU 72, BEBINCA WILL MOVE INLAND INTO VIETNAM AND DISSIPATE BY TAU 96. DUE TO THE WEAK STEERING FLOW IN THE EARLY PART OF THE FORECAST, AND THE LARGE SPREAD IN MODEL TRACK SPEEDS, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN