WDPN32 PGTW 101500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (TWENTYSEVEN) WARNING NR 04// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 225 NM SOUTH OF TAIPEI, TAIWAN, HAS TRACKED WEST-SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A SMALL, SLOWLY CONSOLIDATING SYSTEM WITH FLARING CENTRAL CONVECTION AND SHALLOW FORMATIVE BANDS LOOSELY WRAPPING INTO AN OBSCURED LOW LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH BETTER CONFIDENCE USING A COMPOSITE RADAR LOOP FROM TAIWAN CENTRAL WEATHER BUREAU THAT SHOWS A RAGGED LLC FEATURE THAT HAS SHRUNK IN DIAMETER. THIS LLC ALSO LINED UP WELL WITH A PARTIALLY OBSCURED BUT DISCERNIBLE MICROWAVE LLC FEATURE ON THE 101038Z 91 GHZ SSMIS PASS. THE INITIAL INTENSITY OF 35 KNOTS IS BASED ON THE PGTW DVORAK INTENSITY ESTIMATE OF T2.5 AND IS SUPPORTED BY NEARBY SURFACE OBSERVATIONS. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH MODERATE NORTHEASTERLY VERTICAL WIND SHEAR (VWS) PARTLY OFFSET BY A SOLID EQUATORWARD OUTFLOW. SST (29-30C) AND OCEAN HEAT CONTENT ARE CONDUCIVE. THE CYCLONE IS TRACKING UNDER THE STEERING INFLUENCE OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS WARNING. B. TS 27W SHOULD CONTINUE TRACKING WEST-SOUTHWESTWARD THROUGH TAU 72 WITH A SLOW INTENSIFICATION RATE, PEAKING AT 45 KNOTS BY TAU 48. BEFORE TAU 72, THE CYCLONE WILL MAKE LANDFALL OVER THE LUICHOW PENINSULA, CHINA. NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT; HOWEVER, GIVEN THE FORMATIVE NATURE OF THE SYSTEM, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE TRACK FORECAST. C. AFTER TAU 72, TS 27W WILL CONTINUE ON A MORE WESTWARD TRACK AND CROSS THE GULF OF TONKIN, MAKING A FINAL LANDFALL OVER NORTHERN VIETNAM JUST EAST OF HANOI. DUE TO INTERACTION WITH LAND AND INCREASING VWS, THE SYSTEM WILL ERODE AND DISSIPATE BY TAU 96 AS IT TRACKS FURTHER INLAND. NUMERICAL MODEL GUIDANCE SIGNIFICANTLY SPREADS, ALSO LENDING LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST TRACK.// NNNN