MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR 030// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 444 NM SOUTH-SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI) SATELLITE IMAGERY SHOWS A VERY EXPANSIVE SYSTEM WITH FRAGMENTED CONVECTIVE BANDS SPIRALING IN FROM THE SOUTHWEST INTO A LARGE, RAGGED AND FULLY EXPOSED LOW-LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON THE CENTER OF THE LLC SEEN IN A PARTIAL 130013Z METOP-B ASCAT PASS WHICH ALSO SHOWS A BROAD SWATH OF 45 KNOT WIND BARBS IN THE NORTHEAST QUADRANT. THE INITIAL INTENSITY OF 45 KNOTS IS SET FROM THE AFOREMENTIONED ASCAT PASS AND IS ON THE LOW SIDE OF MULTI-AGENCY DVORAK CURRENT ESTIMATES RANGING FROM T3.0-4.0 (45-65 KNOTS). THIS INTENSITY IS FURTHER SUPPORTED BY A 121146Z SATCON ESTIMATE OF 48 KNOTS. UPPER LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH A LOW DIRECTLY OVER THE LLC WHICH IS INHIBITING CONVECTION. SEA SURFACE TEMPERATURE (SST) REMAINS CONDUCIVE (29-30 DEGREES CELSIUS). THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A BUILDING SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. OVER THE NEXT 36 HOURS, TS 11W WILL CONTINUE ON ITS CURRENT TRACK UNDER THE INFLUENCE OF THE PREVIOUSLY MENTIONED STR. NEAR TAU 36, IT WILL TURN POLEWARD AROUND THE STR AXIS, MAKING LANDFALL OVER WESTERN SHIKOKU NEAR TAU 36. THE MARGINAL CONDITIONS WILL SUSTAIN THE CURRENT INTENSITY UP TO TAU 12. AFTERWARD, INCREASING POLEWARD OUTFLOW AHEAD OF A MID-LATITUDE TROUGH WILL PROMOTE A SLIGHT INTENSIFICATION TO A PEAK OF 50 KNOTS BY TAU 24. LAND INTERACTION, INCREASING VWS, AND COOLER SST (24-26 DEGREES CELSIUS) IN THE SEA OF JAPAN (SOJ) WILL COMBINE TO GRADUALLY WEAKEN THE SYSTEM DOWN TO 40 KNOTS BY TAU 72 AS IT EXITS INTO THE SOJ. NUMERICAL MODELS ARE IN GOOD AGREEMENT, WITH THE EXCEPTION OF NAVGEM, WHICH IS EXPECTING AN EARLIER RECURVE, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST. C. AFTER TAU 72, COOLER SST IN THE SOJ WILL COMBINE WITH INCREASED SHEAR TO RAPIDLY WEAKEN THE SYSTEM DOWN TO 35 KNOTS BY TAU 96 AS IT ACCELERATES INTO THE NORTHERN SOJ WEST OF HOKKAIDO. TS 11W WILL BEGIN EXTRA-TROPICAL TRANSITION AS IT ENTERS THE BAROCLINIC ZONE, BECOMING A COLD CORE LOW WITH AN EXPANSIVE WIND FIELD, BY TAU 96. WITH THE EXCEPTION OF NAVGEM, NUMERICAL MODEL DIFFERENCE SPREADS OUT TO 250 NM, BY TAU 96. THERE IS OVERALL MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK FOR THIS PORTION OF THE FORECAST THAT IS LAID JUST TO THE LEFT OF CONSENSUS TO OFFSET THE UNLIKELY NAVGEM/JGSM SOLUTION THAT DRIVES THE VORTEX INTO THE STR.// NNNN NNNN