MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (MITAG) WARNING NR 020// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 19W (MITAG), LOCATED APPROXIMATELY 320 NM SOUTHWEST OF PUSAN, SOUTH KOREA, HAS TRACKED NORTHEASTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. DESPITE THE RAPID DECAY OF DEEP CONVECTION OVER THE PAST 12 HOURS, ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS TIGHTLY-CURVED LOW-LEVEL BANDING WRAPPING INTO A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER, WHICH SUPPORTS THE CURRENT POSITION WITH HIGH CONFIDENCE. THIS WELL-DEFINED LOW-LEVEL STRUCTURE IS ALSO EVIDENT IN A 012309Z SSMIS 91GHZ COLOR COMPOSITE IMAGE WITH LIMITED DEEP CONVECTION SHEARED WELL NORTH OF THE CENTER. A 020118Z ASCAT-B IMAGE INDICATES 40-45 KNOT WINDS (10-MINUTE AVERAGE) OVER THE EASTERN SEMICIRCLE WITH EXTENSIVE GALE-FORCE WINDS. THE CURRENT INTENSITY IS ASSESSED SLIGHTLY HIGHER AT 55 KNOTS BASED ON CURRENT INTENSITY ESTIMATES OF 3.5 (55 KNOTS) CONSISTENT WITH A 012308Z SATCON ESTIMATE OF 50 KNOTS. THE SYSTEM IS CURRENTLY LOCATED WITHIN A BROAD UPPER-LEVEL SUBTROPICAL TROUGH, WHICH IS CONTRIBUTING TO THE RAPID DECAY OF THE DEEP CONVECTIVE STRUCTURE AND PRODUCING STRONG (30-35 KNOTS) SOUTHWESTERLY VERTICAL WIND SHEAR (VWS). SST VALUES ARE MARGINAL AT 24-25C. TS 19W IS TRACKING ALONG THE NORTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE 34-KNOT WIND RADII HAVE BEEN ADJUSTED BASED ON AVAILABLE SURFACE AND SHIP OBSERVATIONS. B. TS 19W IS FORECAST TO ACCELERATE NORTH-NORTHEASTWARD TO NORTHEASTWARD THROUGH TAU 24 AS IT ROUNDS THE STR AXIS. TS 19W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 24 AS IT INTERACTS WITH THE MIDLATITUDE WESTERLIES AND BAROCLINIC ZONE. THE SYSTEM SHOULD GRADUALLY WEAKEN DUE TO INCREASING VWS, COOLER SST AND INTERACTION WITH LAND. 19W WILL TRACK OVER THE SEA OF JAPAN AFTER TAU 30 AND WILL COMPLETE ETT NEAR TAU 48 AS IT GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED WITHIN STRONG MIDLATITUDE WESTERLY FLOW. SST VALUES WILL DECREASE TO LESS THAN 24C, WHICH WILL FURTHER AID IN WEAKENING THE SYSTEM. NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT WITH A 70NM SPREAD IN SOLUTIONS AT TAU 36, THEREFORE, THERE IS HIGH CONFIDENCE (LOW UNCERTAINTY) IN THE JTWC FORECAST TRACK THROUGH TAU 36. AFTER TAU 48, THIS COLD-CORE EXTRA-TROPICAL LOW WILL ACCELERATE EAST-NORTHEASTWARD OVER NORTHERN HONSHU. THE SYSTEM IS STILL EXPECTED TO MAINTAIN GALE-FORCE WINDS. DUE TO THE BROAD NATURE OF THIS LOW AND THE LARGE SPREAD IN THE NUMERICAL MODELS, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN