WDPN31 PGTW 061500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (OMAIS) WARNING NR 09// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 07W (OMAIS), LOCATED APPROXIMATELY 676 NM SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A SLIGHT WEAKENING AND DETERIORATION OF THE DEEP CONVECTION WRAPPING INTO THE BROAD LOW LEVEL CIRCULATION CENTER (LLCC). THE WEAKENING CONVECTIVE STRUCTURE IS ATTRIBUTED TO THE DIURNAL CYCLE. A 061211Z GPM MICROWAVE IMAGE DEPICTS AN EXPANDING MICROWAVE EYE FEATURE THAT SUPPORTS THE INITIAL POSITION WITH FAIR CONFIDENCE. THE CURRENT INTENSITY IS HELD AT 60 KNOTS BASED ON UNCHANGED DVORAK INTENSITY ESTIMATES OF T3.5 (55 KNOTS) AND A RECENT SATCON INTENSITY ESTIMATE OF 66 KNOTS. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH RADIAL OUTFLOW, LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS), AND WARM SEA SURFACE TEMPERATURES (SSTS). TS 07W IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF THE DEEP-LAYERED SUB-TROPICAL RIDGE (STR) POSITIONED TO THE EAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 07W WILL CONTINUE TO TRACK NORTH TO NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE STEERING STR. DURING THIS TIME, TS OMAIS WILL CONTINUE TO INTENSIFY UNDER FAVORABLE ENVIRONMENTAL CONDITIONS AT A SLOW RATE DUE TO THE BROAD NATURE OF THE CYCLONE. CONCURRENTLY, THE CYCLONE WILL CONTINUE TO CONSOLIDATE AROUND THE LLCC AND THE WIND FIELD WILL BECOME SMALLER THROUGHOUT THE FORECAST PERIOD. BY TAU 48, THE SYSTEM WILL REACH ITS MAXIMUM INTENSITY NEAR THE STR AXIS BEFORE IT BEGINS TO ACCELERATE NORTHEASTWARD. TS 07W WILL BEGIN EXTRATROPICAL TRANSITION (ETT) BY TAU 72 AS IT INTERACTS WITH A MID- LATITUDE TROUGH APPROACHING FROM THE NORTHWEST. AS THE SYSTEM ACCELERATES NORTHEASTWARD IT WILL WEAKEN DUE TO DECREASING SSTS AND INCREASING VWS. C. IN THE EXTENDED PERIOD, TS 07W WILL COMPLETE ETT AS A STRONG COLD-CORE LOW AS IT EMBEDS WITHIN THE MID-LATITUDE WESTERLIES AND ACCELERATES NORTHEASTWARD. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT ON THE OVERALL TRACK AND REMAINS CONSISTENT WITH THE SYNOPTIC STEERING PATTERN; THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST./=