MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (MEGI) WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 20W (MEGI), LOCATED APPROXIMATELY 644 NM SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER WITH DEEP CONVECTIVE BANDING WRAPPING INTO A FORMATIVE BUT RAGGED EYE. A 240709Z SSMIS 91GHZ IMAGE REVEALS THE BULK OF THE DEEP CONVECTIVE BANDING OVER THE EASTERN SEMI-CIRCLE, HOWEVER, CONVECTIVE BANDING NOW WRAPS TIGHTLY AROUND THE WESTERN SEMI-CIRCLE INTO A DEFINED CENTER. CONSEQUENTLY, THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION AND RECENT TRACK MOTION. ADDITIONALLY, DVORAK INTENSITY ESTIMATES HAVE INCREASED AND NOW RANGE FROM T3.5 TO T4.0 (55 TO 65 KNOTS) WITH A 240513Z SATCON ESTIMATE OF 60 KNOTS. THE CURRENT INTENSITY IS ASSESSED AT 60 KNOTS BASED ON AN AVERAGE OF THE DVORAK ESTIMATES. ANIMATED WATER VAPOR IMAGERY REVEALS RADIAL OUTFLOW, ENHANCED BY A STRONG TUTT CELL TO THE EAST. OVERALL, ENVIRONMENTAL CONDITIONS TO INCLUDE LOW VERTICAL WIND SHEAR AND WARM SST ARE FAVORABLE FOR FURTHER DEVELOPMENT. TS MEGI IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP LAYERED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TS 20W WILL CONTINUE TO TRACK WEST-NORTHWESTWARD IN A STRAIGHT-RUNNER PATTERN THROUGH TAU 72 WHILE INTENSIFYING RAPIDLY UNDER VERY FAVORABLE CONDITIONS. THE STR IS EXPECTED TO REMAIN STRONG AND EAST-WEST ORIENTED THROUGH THE FORECAST PERIOD. AS A RESULT, THE DYNAMIC GUIDANCE IS IN EXCELLENT AGREEMENT WITH A 75-NM SPREAD IN SOLUTIONS AT TAU 72, JUST PRIOR TO LANDFALL ALONG THE SOUTHEAST COAST OF TAIWAN. THE SYSTEM IS FORECAST TO PEAK AT 105 KNOTS BY TAU 48. C. AFTER TAU 72, TS MEGI WILL CROSS OVER SOUTHERN TAIWAN AND WEAKEN SIGNIFICANTLY DUE TO LAND INTERACTION. AFTER RE-EMERGING OVER THE TAIWAN STRAIT, THE SYSTEM WILL MAKE LANDFALL AGAIN OVER SOUTHEAST CHINA NEAR TAU 96, AND WILL BEGIN DISSIPATING AS IT TRACKS FURTHER INLAND. DUE TO THE TIGHT MODEL AGREEMENT IN THE EXTENDED TAUS, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS.// NNNN NNNN