MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (FRANCISCO) WARNING NR 13// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 09W (FRANCISCO), LOCATED APPROXIMATELY 470 NM EAST-SOUTHEAST OF SASEBO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 16 KNOTS (KTS) OVER THE PAST SIX HOURS. THE LOW LEVEL CIRCULATION CENTER (LLCC) IS BEING OBSCURED BY A SMALL (ROUGHLY 110 NM WIDE) CENTRAL DENSE OVERCAST IN ANIMATED ENHANCED INFRARED SATELLITE IMAGERY WITH DRIER AIR WRAPPING AROUND THE PERIPHERY FROM THE SOUTH. THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION BASED ON A 041703Z ATMS 88 GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 50 KTS FALLS BETWEEN MULTI-AGENCY DVORAK FIXES FROM T3.0-T3.5 (45-55 KTS). THE ENVIRONMENT IS MARGINALLY FAVORABLE WITH LOW (05-10 KNOTS) VERTICAL WIND SHEAR (VWS), WARM (28-29 CELSIUS) SEA SURFACE TEMPERATURE (SST), AND FAIR RADIAL OUTFLOW BEING OFFSET BY DRY AIR ENTRAINMENT FROM AN AREA OF UPPER-LEVEL CONVERGENCE TO THE SOUTHWEST. TS 09W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. THROUGH TAU 36, TS 09W WILL CONTINUE TO TRACK NORTHWESTWARD AND PASS NEAR SASEBO JUST PRIOR TO TAU 30. ADDITIONALLY, THE SYSTEM WILL ROUND THE STR AXIS BETWEEN TAU 36 AND 48, MAKE LANDFALL NEAR BUSAN, KOREA NEAR TAU 40, AND BEGIN EXTRATROPICAL TRANSITION (ETT) AS IT BEGINS INTERACTING WITH THE MID-LATITUDE BAROCLINIC ZONE AROUND TAU 72. MODEL GUIDANCE IS IN EXCELLENT AGREEMENT THROUGH TAU 36. AFTER TAU 36, SPREAD REMAINS GOOD BUT BEGINS TO GRADUALLY INCREASE DUE TO MINOR DIFFERENCES IN THE STRENGTH AND POSITION OF THE STR. SLIGHT INTENSIFICATION IS EXPECTED UNTIL LANDFALL OVER KYUSHU AROUND TAU 24. AFTER TAU 24, THE SYSTEM IS EXPECTED TO WEAKEN DUE TO LAND INTERACTION. HOWEVER, THE CONTINUED FAST FORWARD SPEED SHOULD MINIMIZE THE AMOUNT OF WEAKENING OVER KYUSHU PRIOR TO PASSING NEAR SASEBO. BASED ON THE OVERALL EXCELLENT AGREEMENT OF THE MODELS AND THE STEADY PRESENCE OF THE STR, CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST IS HIGH. C. AFTER TAU 72, TS 09W WILL CONTINUE TRACKING EAST-NORTHEASTWARD UNTIL COMPLETING ETT SOMETIME BETWEEN TAU 96 AND 120. THROUGHOUT THIS PERIOD, COOL SST AND HIGH VWS SHOULD WEAKEN THE SYSTEM. TAKING INTO ACCOUNT THAT ALONG-TRACK SPREAD IN THE MODEL GUIDANCE TYPICALLY INCREASES SIGNIFICANTLY AFTER A SYSTEM BECOMES EMBEDDED IN THE MID- LATITUDE WESTERLIES, THERE IS RELATIVELY GOOD AGREEMENT IN THE GUIDANCE, MAKING FOR FAIR CONFIDENCE IN THE EXTENDED TRACK FORECAST.// NNNN NNNN