WDPN31 PGTW 190300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (IN-FA) WARNING NR 09// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 27W (IN-FA), LOCATED APPROXIMATELY 59 NM EAST OF CHUUK, FSM, HAS TRACKED NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS MAINTAINED A COMPACT CONVECTIVE SIGNATURE. THE INITIAL POSITION IS BASED ON THE MSI ANIMATION AND SUPPORTED BY A 182132Z SSMI-S MICROWAVE PASS WITH GOOD CONFIDENCE. THE INITIAL INTENSITY OF 55 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES THE CYCLONE IS IN AN AREA OF LIGHT (05-10 KNOT) VERTICAL WIND SHEAR (VWS) AND GOOD NORTHEASTWARD AND EQUATORWARD OUTFLOW. HOWEVER, THERE IS SUBSIDENCE OCCURRING ALONG THE NORTHWEST PERIPHERY, AS EVIDENT ON ANIMATED WATER VAPOR IMAGERY. ALONG-TRACK SEA SURFACE TEMPERATURES ARE AT 29- 30 DEGREES CELSIUS. TS 27W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE PREVIOUS FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 27W WILL CONTINUE TO TRACK WEST-NORTHWESTWARD AND WILL GRADUALLY RE-INTENSIFY AS ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE, REACHING 95 KNOTS BY TAU 48. C. BEYOND TAU 72, TS IN-FA WILL TRACK MORE POLEWARD AS A MINOR MID-LATITUDE TROUGH CREATES A WEAKNESS IN THE STR AND THE SYSTEM WILL BEGIN TO ROUND THE RIDGE AXIS. INCREASING VWS ASSOCIATED WITH THE STRONG MID-LATITUDE WESTERLIES WILL BEGIN TO ERODE THE SYSTEM. DYNAMIC MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT WITH SOME SPREADING AT THE END OF THE FORECAST TRACK. IN VIEW OF THIS, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 96 ONLY.// NNNN