MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR 031// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 11W (KROSA), LOCATED APPROXIMATELY 422 NM SOUTH-SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A BROAD 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 BASED WITH FAIR CONFIDENCE ON THE ROUGH CENTROID OF ROTATION IN THE MSI IMAGERY, ALTHOUGH MULTIPLE SMALL MESOVORTICES ARE ALSO VISIBLE IN THE LLC. THE INITIAL INTENSITY OF 45 KNOTS AGREES WITH THE PGTW DVORAK CURRENT INTENSITY ESTIMATE OF T3.0 (45 KTS) AND IS SLIGHTLY BELOW A 130326Z SATCON ESTIMATE OF 48 KTS. UPPER LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH AN UPPER LEVEL LOW DIRECTLY OVER THE LLC WHICH IS INHIBITING CENTRAL CONVECTION. THE RADIUS OF MAXIMUM WINDS, LIKE THE CONVECTION, IS DISPLACED FAR FROM THE CENTER. SEA SURFACE TEMPERATURES (SST) REMAIN CONDUCIVE (29-30 DEGREES CELSIUS). THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF AN EXTENSION OF THE 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, A MIDLATITUDE TROUGH WILL APPROACH FROM THE WEST, ERODING THE STR AND ALLOWING TS 11W TO RECURVE POLEWARD AROUND THE STR AXIS, SKIRTING WESTERN SHIKOKU NEAR TAU 36. THE MARGINAL CONDITIONS WILL SUSTAIN THE CURRENT INTENSITY UP TO TAU 12. AFTERWARD, INCREASING POLEWARD OUTFLOW AHEAD OF THE AFOREMENTIONED TROUGH WILL ENABLE A SLIGHT INTENSIFICATION TO A PEAK OF 50 KNOTS BY TAU 24. LAND INTERACTION, INCREASING VERTICAL WIND SHEAR (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 CROSS-TRACK AGREEMENT, WITH THE EXCEPTION OF NAVGEM, WHICH IS EXPECTING AN EARLIER RECURVE AND TRACKS MUCH FURTHER EAST THAN THE OTHER MODELS. ADDITIONALLY, ECMWF AND UKMET PREDICT FASTER ALONG-TRACK SPEEDS THAN DO GFS AND THE GFS ENSEMBLE. THE JTWC FORECAST TRACK IS HEDGED SLIGHTLY AHEAD AND TO THE WEST OF THE MULTI-MODEL CONSENSUS, TOWARDS THE ECMWF SOLUTION, WITH HIGH CONFIDENCE. C. AFTER TAU 72, COOLER SSTS IN THE SOJ WILL COMBINE WITH INCREASING VWS TO RAPIDLY WEAKEN THE SYSTEM TO 35 KNOTS BY TAU 96 AS IT ACCELERATES INTO THE NORTHERN SOJ WEST OF HOKKAIDO. TS 11W WILL ALSO BEGIN EXTRA-TROPICAL TRANSITION AS IT INTERACTS WITH THE AFOREMENTIONED TROUGH. WITH THE EXCEPTION OF NAVGEM, THE CROSS-TRACK MODEL SPREAD BECOMES 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, TOWARDS THE ECMWF SOLUTION, AND HEDGED AWAY FROM THE NAVGEM SOLUTION THAT DRIVES TS 11W INTO THE RIDGING.// NNNN NNNN