WDPN32 PGTW 200300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (AMPIL) WARNING NR 10// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 12W (AMPIL), LOCATED APPROXIMATELY 279 NM SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED NORTH-NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH IMPROVED CONVECTIVE BANDING. A 192137Z SSMIS 37GHZ IMAGE REVEALS TIGHTLY- CURVED BANDING WRAPPING INTO A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC), WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE, COMPLEX ENVIRONMENT WITH TWO TUTT CELLS POSITIONED OVER THE NORTH AND WEST QUADRANTS. HOWEVER, THE UPPER-LEVEL ENVIRONMENT HAS IMPROVED SLIGHTLY WITH IMPROVED POLEWARD OUTFLOW, WHICH HAS ALLOWED DEEP CONVECTION TO CONSOLIDATE OVER THE LLCC. SST VALUES (27-28C) REMAIN FAVORABLE WHILE OCEAN HEAT CONTENT VALUES ARE LOW AND UNFAVORABLE. THE INITIAL INTENSITY IS ASSESSED AT 50 KNOTS, HEDGED ABOVE DVORAK INTENSITY ESTIMATES OF T3.0 (45 KNOTS) BASED ON THE IMPROVED CONVECTIVE STRUCTURE. TS 12W IS LOCATED WEST OF AN EXTENSION OF THE NEAR-EQUATORIAL RIDGE (NER) AND SOUTH OF A STRONG EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 12W IS FORECAST TO TURN NORTHWESTWARD AS IT TRANSITIONS TO THE STEERING INFLUENCE OF THE STR TO THE NORTH. DUE TO THE MARGINALLY-FAVORABLE UPPER-LEVEL ENVIRONMENT, WHICH IS FORECAST TO PERSIST, TS AMPIL IS EXPECTED TO INTENSIFY AT A SLOWER-THAN- CLIMATOLOGICAL RATE OF 10 KNOTS PER DAY THROUGH TAU 24. THE SYSTEM SHOULD PEAK AT TAU 24 TO 60 KNOTS. THE NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A 80NM SPREAD IN SOLUTIONS AT TAU 24. THE BULK OF THE GUIDANCE INDICATES A TRACK OVER AND TO THE SOUTH OF OKINAWA. AFTER TAU 36, TS 12W IS FORECAST TO ACCELERATE NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR AND IS EXPECTED TO MAKE LANDFALL NEAR TAU 48 ALONG THE EAST COAST OF CHINA, SOUTH OF SHANGHAI. SURFACE WINDS ARE FORECAST TO REMAIN EXTENSIVE AND ROBUST OVER THE NORTHERN SEMICIRCLE DUE TO THE STRONG GRADIENT ASSOCIATED WITH THE SYSTEM AND ADJACENT SURFACE HIGH. C. AFTER TAU 72, THE SYSTEM WILL CONTINUE TO TRACK INLAND WHILE WEAKENING RAPIDLY. OVERALL, THERE IS NOW HIGH CONFIDENCE IN THE JTWC FORECAST TRACK (I.E., LOW UNCERTAINTY), WHICH IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS.// NNNN