WDPN32 PGTW 241500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (EWINIAR) WARNING NR 03// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 19W (EWINIAR), LOCATED APPROXIMATELY 300 NM SOUTH-SOUTHWEST OF IWO-TO, JAPAN, HAS TRACKED NORTHWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS A SLOWLY CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTIVE BANDING OVER THE EASTERN SEMI-CIRCLE WRAPPING INTO THE EAST QUADRANT. A 241227Z METOP-A IMAGE INDICATES A SLIGHTLY ELONGATED BUT IMPROVING LLCC WITH TIGHTLY-CURVED SHALLOW CONVECTIVE BANDING OVER THE WESTERN SEMI-CIRCLE. AS DEPICTED IN ANIMATED WATER VAPOR IMAGERY AND RECENT UW-CIMSS SHEAR PRODUCTS, THE UPPER-LEVEL ENVIRONMENT HAS REMAINED MARGINAL DUE TO MODERATE, WESTERLY VERTICAL WIND SHEAR (VWS) ASSOCIATED WITH THE OUTFLOW FROM STY 18W. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS, WHICH IS SLIGHTLY HIGHER THAN THE DVORAK ESTIMATES OF 30 KNOTS, BASED ON A 241227Z ASCAT IMAGE SHOWING 35-KNOT WINDS OVER THE EASTERN SEMI-CIRCLE. THE INITIAL POSITION IS BASED ON RECENT FIXES AND THE 241227Z METOP-A IMAGE WITH FAIR CONFIDENCE. TS 19W IS CURRENTLY TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF THE LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 19W IS FORECAST TO TRACK GENERALLY NORTH-NORTHEASTWARD THROUGH THE PERIOD AND SHOULD INTENSIFY TO A PEAK INTENSITY NEAR 45 KNOTS BY TAU 24 DUE TO INCREASING POLEWARD OUTFLOW ASSOCIATED WITH THE APPROACHING MIDLATITUDE SHORTWAVE TROUGH AND DECREASING VWS. AFTER TAU 48, TS 19W IS FORECAST TO ENCOUNTER AN INCREASINGLY HOSTILE ENVIRONMENT AS IT TRACKS ALONG AND INTO THE LEADING EDGE OF THE AFOREMENTIONED SHORTWAVE TROUGH. THE SYSTEM MAY ENCOUNTER WEAK BAROCLINICITY ASSOCIATED WITH THE SUBTROPICAL TROUGH; HOWEVER, THERE IS NO EVIDENCE THAT TS 19W WILL UNDERGO EXTRA-TROPICAL TRANSITION UNTIL WELL AFTER THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE IS IN FAIR AGREEMENT, THEREFORE, THE JTWC TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS. C. IN THE EXTENDED TAUS, TS 19W IS FORECAST TO WEAKEN RAPIDLY DUE TO COOLER SST AND INCREASING VWS AND WILL ACCELERATE NORTHEASTWARD. DYNAMIC GUIDANCE REMAINS IN FAIR AGREEMENT. DUE TO THE PRESENCE OF STRONG WESTERLY FLOW OVER HONSHU, TS 19W IS NOT EXPECTED TO IMPACT THE KANTO PLAIN AND SHOULD ALSO WEAKEN RAPIDLY SOUTHEAST AND EAST OF HONSHU. THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK.// NNNN