WDPN32 PGTW 211500 MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM (TS) 04W WARNING NR 08// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 211200Z6 TO 241200Z9 JUN 01. A. TROPICAL STORM (TS) 04W (CHEBI), LOCATED APPROXIMATELY 260 NM SOUTHEAST OF PORT SAN VICENTE, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS DURING THE PAST SIX HOURS. THE WARNING POSITION IS BASED ON 211130Z8 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS. ANIMATED SATELLITE IMAGERY DEPICTS CYCLING OF THE CONVECTIVE BANDS AROUND THE LOW-LEVEL CIRCULATION CENTER. WATER VAPOR IMAGERY INDICATES A MID TO UPPER LEVEL RIDGE POSITIONED NORTH OF THE SYSTEM. B. THE MID-LEVEL SUBTROPICAL RIDGE EXTENDING WESTWARD FROM A HIGH NORTH OF THE MARIANA ISLANDS SHOULD MAINTAIN STRENGTH THROUGH THE FORECAST PERIOD. THEREFORE, TS 04W IS FORECAST TO TRACK NORTHWESTWARD JUST NORTH OF LUZON. THE NOGAPS MODEL AND THE NAVY GEOPHYSICAL FLUID DYNAMICS (GFDN) MODEL ARE IN FAIR AGREEMENT TRACKING THE SYSTEM WEST-NORTHWESTWARD THROUGH THE FORECAST PERIOD. THE JMA GLOBAL SPECTRAL AND THE JMA TYPHOON MODELS TRACK THE SYSTEM MORE NORTHWESTWARD. THE UKMET OFFICE MODEL (EGRR) LOSES THE SYSTEM AFTER 24 HOURS. THE NUMERICAL CONSENSUS CONSISTS OF 4 MODELS. THE OFFICIAL FORECAST IS BASED ON A BLEND OF PERSISTENCE WITH A SELECTED CONSENSUS OF 4 MODELS (NOGAPS, GFDN, JGSM, JTYM). C. THE SYSTEM SHOULD INTENSIFY SLOWLY AS IT TRACKS NORTHWESTWARD INTO A MORE FAVORABLE UPPER LEVEL ENVIRONMENT. D. THE WIND RADII IS BASED ON CLIMATOLOGY. FORECAST TEAM: MAZANY/PARKER/EDBERG//