WDPN31 PGTW 051500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (DUJUAN)/ WARNING NR 09// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 13W (DUJUAN), LOCATED APPROXIMATELY 430 NM EAST-SOUTHEAST OF OKINAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED INFRARED SATELLITE IMAGERY SHOWS DEEP CONVECTION CONTINUES TO DEVELOP OVER LOW LEVEL CIRCULATION CENTER. ANIMATED WATER VAPOR IMAGERY SUGGESTS THAT OUTFLOW IN THE POLEWARD AND EQUATORWARD CHANNELS HAS PERSISTED ALLOWING THE DEEP CONVECTIVE DEVELOPMENT TO PERSIST. THE CURRENT POSITION IS BASED ON A 051130Z PGTW FIX AND A 050839Z WINDSAT PASS. THE CURRENT INTENSITY ESTIMATE OF 45 KNOTS IS CONSISTENT WITH DVORAK T-NUMBER VALUES OF 3.0 FROM RJTD AND KNES. 3. FORECAST REASONING. A. THE GENERAL FORECAST PHILOSOPHY HAS NOT CHANGED SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TS 13W IS EXPECTED TO TRACK INCREASINGLY POLEWARD OVER THE NEXT 36 HOURS UNDER THE CONTINUED STEERING INFLUENCE OF SUBTROPICAL RIDGING TO THE EAST. AFTER TAU 36 THE TROPICAL STORM WILL CREST THE STEERING RIDGE AXIS AND TURN NORTHEASTWARD AHEAD OF AN APPROACHING MIDLATITUDE TROUGH. THE TROPICAL STORM SHOULD INTENSIFY STEADILY OVER THE NEXT 48 HOURS AS POLEWARD AND EQUATORWARD OUTFLOW ALOFT REMAIN FAVORABLE. HOWEVER, THE CYCLONE IS EXPECTED TO MAINTAIN INTENSITY BETWEEN TAU 48 AND TAU 72 AS WESTERLY VERTICAL WIND SHEAR BEGINS TO INCREASE. C. TS 13W WILL ACCELERATE INTO THE MIDLATITUDE WESTERLY FLOW PATTERN AFTER TAU 48, STARTING EXTRATROPICAL TRANSITION BY TAU 72 AND BECOMING FULLY BAROCLINIC BY TAU 96. VERTICAL WIND SHEAR WILL INCREASE SIGNIFICANTLY DURING THIS EXTENDED PERIOD, RESULTING IN A STEADY WEAKENING TREND AS THE CYCLONE ACCELERATES NORTHEASTWARD. THE AVAILABLE NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE CURRENT FORECAST. FORECAST TEAM: BRAVO.// NNNN