WDPN31 PGTW 201500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 07// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 15W (TEMBIN), LOCATED APPROXIMATELY 420 NM SOUTH- SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTH-NORTHEASTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY AND A 201157Z SSMIS IMAGE INDICATE IMPROVED EYEWALL CONSOLIDATION OVER THE PAST SIX HOURS WITH A 25 NM ROUND EYE EVIDENT SURROUNDED BY A MORE SYMMETRIC EYEWALL WITH COLDER CLOUD TOP TEMPERATURES. THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION BASED ON THE ROUND EYE STRUCTURE IN SATELLITE IMAGERY. UPPER-LEVEL ANALYSIS INDICATES NEAR- RADIAL OUTFLOW WITH POLEWARD OUTFLOW ENHANCED BY A STRONG TUTT CELL NEAR 27N 135E. THE ONLY LIMITING FACTOR EVIDENT IN ANIMATED WATER VAPOR IMAGERY IS CONVERGENT FLOW OVER THE NORTHWEST PERIPHERY OF THE SYSTEM. AS A RESULT OF THE VERY FAVORABLE ENVIRONMENTAL CONDITIONS, TY 15W HAS RAPIDLY INTENSIFIED OVER THE PAST 24 HOURS GOING FROM A 45-KNOT INTENSITY AT 19/12Z TO THE 20/12Z INITIAL INTENSITY OF 110 KNOTS, WHICH IS BASED ON AN AVERAGE OF THE LATEST DVORAK ESTIMATES RANGING FROM 102 KNOTS (RJTD, KNES) TO 115 KNOTS (PGTW). TY 15W IS EMBEDDED WITHIN A WEAK STEERING ENVIRONMENT AND HAS TRACKED SLOWLY AND ERRATICALLY NORTHWARD ALONG THE NORTHWEST PERIPHERY OF THE LOW- TO MID-LEVEL NEAR-EQUATORIAL RIDGE (NER). 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 15W IS FORECAST TO TRACK SLOWLY NORTHWARD TO NORTH- NORTHWESTWARD WITHIN A WEAK STEERING ENVIRONMENT THROUGH TAU 36. NEAR TAU 36, A DEEP MIDLATITUDE TROUGH WILL TRACK ACROSS THE KOREAN REGION RESULTING IN A TEMPORARY SLOW-DOWN OR PERHAPS QUASI- STATIONARY MOTION EAST OF TAIWAN; HOWEVER, THIS IS EXPECTED TO BE SHORT-LIVED AS THE TROUGH IS EXPECTED TO RAPIDLY TRANSIT EASTWARD. AFTER TAU 48, THE SUBTROPICAL RIDGE IS FORECAST TO RE-BUILD OVER EASTERN CHINA AND THE EAST CHINA SEA PROVIDING A WESTWARD STEERING INFLUENCE. TY 15W IS FORECAST TO CONTINUE INTENSIFYING THROUGH TAU 72 UNDER FAVORABLE CONDITIONS AND SHOULD REACH A PEAK INTENSITY OF 125 KNOTS PRIOR TO MAKING LANDFALL OVER TAIWAN. C. IN THE EXTENDED TAUS, TY 15W SHOULD ACCELERATE AND TRACK WESTWARD INTO THE TAIWAN STRAIT AND WILL MAKE ITS SECOND LANDFALL NORTHEAST OF HONG KONG NEAR TAU 96. THE SYSTEM IS EXPECTED TO MAINTAIN MINIMAL TYPHOON STRENGTH AS IT EMERGES OVER THE TAIWAN STRAIT BUT SHOULD WEAKEN SIGNIFICANTLY AFTER SECOND LANDFALL DUE TO FRICTIONAL EFFECTS. THE BULK OF THE DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A 170 NM SPREAD AT TAU 120; HOWEVER, THE UKMO MODEL ERRONEOUSLY DRIVES THE SYSTEM NORTHWARD INTO THE STR AND IS DISCOUNTED. ADDITIONALLY, THE GFS MODEL IS NOW INDICATING STRONG BINARY INTERACTION WITH TS 16W AFTER TAU 72, WHICH IS DEEMED UNLIKELY AT THIS POINT. THE TWO SYSTEM CENTERS ARE CURRENTLY SEPARATED BY 930 NM AND, BASED ON THE 20/12Z FORECASTS, WILL APPROACH TO ABOUT 680 NM BY TAU 72. UNLESS THERE IS A SIGNIFICANT TRACK CHANGE I.E., A LONGER QUASI-STATIONARY PERIOD EAST OF TAIWAN, BINARY INTERACTION IS UNLIKELY. OVERALL, THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK.// NNNN