WDPN32 PGTW 201500 MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (NARI) WARNING NR 59// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 201200Z5 TO 221200Z7 SEP 01. A. TROPICAL STORM (TS) 20W (NARI), LOCATED APPROXIMATELY 25 NM NORTH OF HONG KONG HAS TRACKED WESTWARD AT 14 KNOTS DURING THE PAST SIX HOURS. THE WARNING POSITION IS BASED ON 201130Z7 INFRARED SATELLITE IMAGERY AND SYNOPTIC REPORTS. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 35 KNOTS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS RAPID WEAKENING OF DEEP CONVECTION AND ORGANIZATION OVER THE PAST 6 HOURS. SYNOPTIC DATA (201200Z5) FROM HONG KONG INDICATES NORTHWESTERLY WINDS AT 15 KNOTS SUSTAINED WITH SLP NEAR 1006 MB. B. TS 20W IS FORECAST TO TRACK WESTWARD TO WEST-SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE LOW TO MID LEVEL RIDGE OVER EASTERN CHINA. DYNAMIC AIDS ARE LIMITED AFTER 24 HOURS DUE TO RAPID WEAKENING OF THE SYSTEM. THE NCEP AVIATION (AVN) EXTENDS 72 HOURS AND INDICATES A GENERALLY WESTWARD TRACK. THE NOGAPS, GEOPHYSICAL FLUID DYNAMIC NAVY (GFDN), AND THE UK-MET OFFICE (EGRR) MODELS TRACK THE SYSTEM THROUGH 24 HOURS AND INDICATE A WEST-SOUTHWESTWARD TRACK. OUR FORECAST IS BASED ON PERSISTENCE THROUGH 24 HOURS, AND AFTERWARDS A BLEND OF THE AVN, COLORADO STATE UNIVERSITY MODEL, AND THE BETA ADVECTION MODELS. C. TS 20W REMAINS UNDER A MARGINAL SHEAR ENVIRONMENT, AND IS EXPECTED TO CONTINUE TO WEAKEN AS IT FURTHER INTERACTS WITH LAND. TS 20W IS EXPECTED TO DISSIPATE BY THE 36-48 HOUR POINT. D. SYSTEM DOES NOT MEET WIND RADII CRITERIA. FORECAST TEAM: BARLOW/SMITH/MAYER/TON// BT #XXXX NNNN