WDPN32 PGTW 290300 MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W WARNING NR 09// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 290000Z1 AUG TO 010000Z1 SEP 01. A. TROPICAL STORM (TS) 17W (SEPAT), LOCATED APPROXIMATELY 1000 NM WEST OF MIDWAY ISLAND, HAS TRACKED NORTHWARD AT 13 KNOTS DURING THE PAST SIX HOURS. THE WARNING POSITION IS BASED ON 282330Z8 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT SATELLITE INTENSITY ESTIMATES OF 35 AND 45 KNOTS. A 292009Z2 SSM/I PASS DEPICTED SCATTERED DEEP CONVECTION ASSOCIATED WITH THE SYSTEM. VISIBLE IMAGERY DEPICTS WELL-DEFINED LOW CLOUD LINE FEATURES. B. TS 17W IS TRACKING POLEWARD UNDER THE STEERING INFLUENCE OF A STRONG MID-LEVEL RIDGE CENTERED TO THE NORTHEAST. NOGAPS, THE NAVY GEOPHYSICAL FLUID DYNAMICS-NAVY (GFDN), THE UKMET OFFICE GLOBAL (JGSM) AND THE JMA GLOBAL AND TYPHOON (JTYM) MODELS ARE IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD. TS 17W SHOULD TRACK ALONG THE MID-LEVEL RIDGE FEATURE AND BEGIN RECURVATURE BY THE 36 HOUR POINT. OUR FORECAST IS BASED ON A CONSENSUS OF FIVE MODELS (NOGAPS, GFDN, EGRR, JGSM, JTYM). C. THE SYSTEM IS EXPECTED TO SLOWLY WEAKEN OVER THE NEXT 12 HOURS AS THE SYSTEM TRACKS NORTH OF THE UPPER-LEVEL RIDGE AND OVER COOLER SST. INDICATIONS OF EXTRA TROPICAL TRANSITION APPEAR IN THE MODELS AT THE 48 HOUR POINT. D. FORECAST WIND RADII ARE BASED ON MICROWAVE IMAGERY AND CLIMATOLOGY FOR AN AVERAGE SIZE SYSTEM. FORECAST TEAM: SMITH/MAYER/TON// BT #XXXX NNNN