WDPN31 PGTW 011500 MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (CHATAAN) WARNING NR 15// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 011200Z4 TO 041200Z7 JUL 02. A. TROPICAL STORM (TS) 08W (CHATAAN), LOCATED APPROXIMATELY 220 NM EAST-SOUTHEAST OF CHUUK, HAS TRACKED NORTHWESTWARD AT 04 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON A 010944Z8 SPECIAL SENSOR MICROWAVE IMAGE (SSMI) PASS AND 010530Z9 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS. THE SSMI PASS AND ANIMATED IMAGERY SHOW THAT THE DEEP CONVECTION CONTINUES TO CYCLE WEST OF THE LOW LEVEL CIRCULATION CENTER (LLCC). B. TS 08W IS FORECAST TO TRACK NORTHWESTWARD UNDER THE INFLUENCE OF THE MID-LEVEL HIGH HEIGHT CENTER TO THE NORTH-NORTHEAST. THE AVAILABLE DYNAMIC AIDS CONSISTING OF NCEP AVIATION, NOGAPS, GFDN, AFWA MM5, COAMPS, UKMET GLOBAL (EGRR), AND JAPANESE GLOBAL (JGSM) AND TYPHOON (JTYM) MODELS ARE IN GOOD AGREEMENT WITH THIS SCENARIO. OUR FORECAST IS BASED ON A BLEND OF PERSISTENCE AND A CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS. C. THE UPPER LEVEL LOW TO THE NORTH IS EXPECTED TO DRIFT WEST AND CONTINUE TO PROVIDE A POLEWARD OUTFLOW CHANNEL FOR THE SYSTEM. UW CIMSS ANALYSIS INDICATES THAT THE SYSTEM IS UNDER WEAK TO MODERATE VERTICAL WIND SHEAR. THEREFORE, INTENSIFICATION OVER THE NEXT 12 TO 24 HOURS SHOULD BE SLOW, IF AT ALL. LATE IN THE PERIOD, TS 08W SHOULD MOVE INTO MORE FAVORABLE VERTICAL WIND SHEAR CONDITIONS AND SLOWLY INTENSIFY. D. CURRENT WIND RADII ARE BASED ON THE SSMI PASS AND SYNOPTIC OBSERVATIONS. FORECAST WIND RADII ARE BASED ON PERSISTENCE FOR THE NEXT 24 TO 36 HOURS, AND THEN CLIMATOLOGY FOR AN AVERAGE SIZE SYSTEM. FORECAST TEAM: VILPORS/WAUGAMAN/WARREN/CUTMAN// NNNN