WDPN32 PGTW 160300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 19W (SONCA), LOCATED APPROXIMATELY 630 NM EAST-SOUTHEAST OF CHICHI JIMA, JAPAN, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A PARTIALLY-EXPOSED, WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTIVE BANDING WRAPPING FROM THE WEST QUADRANT INTO THE SOUTHEAST QUADRANT. A 152216Z SSMIS 37 GHZ IMAGE DEPICTS TIGHTLY-CURVED BANDING WRAPPING INTO A WELL- DEFINED LLCC, WHICH IS POSITIONED ON THE EASTERN EDGE OF THE DEEP CONVECTION. RECENT MICROWAVE IMAGERY AND ASCAT DATA OVER THE PAST 24 HOURS SUPPORTS A 45-50 KNOT SYSTEM, THEREFORE, THE CURRENT INTENSITY WAS INCREASED TO 45 KNOTS. DVORAK ESTIMATES RANGE FROM 30- 35 KNOTS AND ARE TOO LOW DUE TO THE LACK OF DEEP CENTRAL CONVECTION. THERE IS HIGH CONFIDENCE IN THE CURRENT POSITION AND MOTION BASED ON THE SSMIS IMAGE. OVER THE PAST 18 HOURS, AN UPPER-LEVEL LOW HAS DEVELOPED AND STRENGTHENED OVER THE CENTER WITH STRONG WESTERLY FLOW AND DRY AIR DIGGING INTO THE SOUTHWEST PERIPHERY OF THE SYSTEM. SIMILAR TO TS 18W, TS 19W APPEARS TO BE TRANSITIONING INTO A HYBRID SYSTEM. AT THIS TIME, AMSU CROSS SECTIONS CONTINUE TO DEPICT A +3C WARM TEMPERATURE ANOMALY TYPICAL OF A TROPICAL CYCLONE. 3. FORECAST REASONING. A. NO CHANGE TO FORECAST PHILOSOPHY. B. TS 19W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP SUBTROPICAL STEERING RIDGE AND IS FORECAST TO ACCELERATE NORTHWESTWARD THROUGH TAU 48 AND THEN RE-CURVE EAST OF TOKYO. MODEL GUIDANCE IS TIGHTLY CLUSTERED WITH THE RECENT EXCEPTION OF THE UKMO TRACKER. ANALYSIS OF THE UKMO 850 MB VORTICITY FIELDS INDICATES THAT THE ACTUAL TRACK IS SIMILAR TO THE OTHER MODELS, HOWEVER, THE COMPLEX TRACKER ERRONEOUSLY JUMPS THE CENTER TO THE BAROCLINIC ZONE FORECAST TO MOVE INTO CENTRAL JAPAN. TS 19W IS EXPECTED TO INTENSIFY SLOWLY DUE TO GENERALLY MARGINAL UPPER-LEVEL CONDITIONS. C. TS 19W WILL CONTINUE TO RE-CURVE AND ACCELERATE EAST- NORTHEASTWARD AS IT BECOMES EMBEDDED WITHIN THE STRONG WESTERLY FLOW. TS 19W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 72 AS IT APPROACHES JAPAN AND WILL COMPLETE ETT EAST OF HONSHU AS IT BECOMES FULLY EMBEDDED IN THE MIDLATITUDE WESTERLIES.// NNNN