MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (TWENTYSEVEN) WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 345 NM EAST-SOUTHEAST OF GUAM, HAS TRACKED SOUTHWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED MULTI-SPECTRAL SATELLITE IMAGERY DEPICTS AN AREA OF BUILDING CONVECTION CENTRALLY LOCATED OVER A LOW-LEVEL CIRCULATION CENTER (LLCC). A 192026Z 27GHZ WINDSAT MICROWAVE IMAGE DEPICTS FORMATIVE BANDING WRAPPING INTO A CENTRAL DEEP CONVECTIVE AREA FROM BOTH THE NORTHERN AND SOUTHERN SEMI- CIRCLES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PGTW SATELLITE FIX AND EXTRAPOLATION FROM A 192224Z OSCAT IMAGE. THE INITIAL INTENSITY OF 35 KNOTS IS HEDGED SLIGHTLY ABOVE THE PGTW DVORAK ESTIMATE OF T2.0 (30 KNOTS) AND IS SUPPORTED BY THE PREVIOUSLY MENTIONED OSCAT IMAGE SHOWING 35 AND 40 KNOT WIND BARBS. ENVIRONMENTAL ANALYSIS REVEALS THAT THE SYSTEM IS IN AN AREA OF LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS) AND IS TRACKING THROUGH WARM (31 CELSIUS) SEA SURFACE TEMPERATURES (SSTS). TS 27W HAS DEVELOPED A POLEWARD OUTFLOW CHANNEL THAT IS FLOWING INTO A TUTT CELL. THE SYSTEM HAS BEEN TRACKING TO THE SOUTH UNDER THE INFLUENCE OF A NEAR EQUATORIAL RIDGE LOCATED TO THE SOUTHWEST AND A BUILDING SUBTROPICAL RIDGE LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THE FORECAST PHILOSOPHY HAS CHANGED AS PEAK INTENSITIES HAVE INCREASED DUE TO A POSSIBLE RAPID INTENSIFICATION SCENARIO. B. TS 27W IS FORECAST TO TRACK NORTHWEST OVER THE NEXT 48 HOURS UNDER THE INFLUENCE OF THE BUILDING SUBTROPICAL RIDGE TO THE NORTHEAST. AFTER TAU 48, THE SYSTEM WILL TRACK MORE NORTH-NORTHWEST AS IT ROUNDS THE RIDGE AXIS. DUE TO THE POLEWARD OUTFLOW CHANNEL BEING ENHANCED BY THE TUTT CELL, A PERIOD OF RAPID INTENSIFICATION IS FORECAST TO OCCUR THROUGH TAU 36, PEAKING AT 60 KNOTS. AFTER TAU 48, TS 27W WILL BEGIN TO WEAKEN AS THE ENVIRONMENT BECOMES UNFAVORABLE DUE TO INCREASING VERTICAL WIND SHEAR, THE RESULT OF THE SYSTEMS PROXIMITY TO TYPHOON 25W. THE WEAKENING TREND WILL PERSIST UNTIL THE SYSTEM IS ABSORBED BY TY 25W AROUND TAU 96. DYNAMIC MODEL GUIDANCE IS IN STRONG AGREEMENT IN THE LATER TAUS FOR THE TRACK DIRECTION. THE INITIAL TRACK DIRECTION HAS NOT TURNED TO THE NORTHWEST AS RAPIDLY AS FORECAST CAUSING UNCERTAINTY IN THE INITIAL FORECAST TRACK. THIS UNCERTAINTY, COMBINED WITH THE COMPLEX NATURE OF THE FORECAST TRACK, LENDS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN