WDPN31 PGTW 060300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (DUJUAN)/ WARNING NR 11// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 13W (DUJUAN), LOCATED APPROXIMATELY 710 NM SOUTH-SOUTHWEST OF TOKYO, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY NOW DEPICTS A PARTIALLY-EXPOSED AND WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH CONVECTIVE BANDING OVER THE WESTERN SEMI-CIRCLE. OVER THE PAST 06 HOURS, DEEP CONVECTION OVER THE LLCC HAS DIMINISHED, HOWEVER, THE SYSTEM HAS MAINTAINED INTENSITY AT 45 KNOTS. THIS IS BASED ON DVORAK ESTIMATES FROM ALL THREE AGENCIES (PGTW, KNES AND RJTD). ANIMATED WATER VAPOR IMAGERY INDICATES IMPROVED POLEWARD OUTFLOW AHEAD OF AN UPPER-LEVEL TROUGH DIGGING OVER WESTERN JAPAN. A WEAK UPPER-LEVEL LOW HAS DEVELOPED WEST OF THE SYSTEM OVER OKINAWA AND APPEARS TO BE BOOSTING POLEWARD OUTFLOW DESPITE SOME PRESSURE ON THE WESTERN PERIPHERY. THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION AND 12-HOUR MOTION BASED ON RECENT VISIBLE IMAGERY AS WELL AS A SERIES OF HIGH RESOLUTION MICROWAVE IMAGES (051246Z TRMM, 051702Z AMSR-E, 052108Z WINDSAT 37 GHZ AND 052231Z SSMIS). TS 13W IS CLEARLY MOVING ALONG A NORTH- NORTHEASTWARD TRAJECTORY. 3. FORECAST REASONING. A. NO CHANGES IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. BASED ON CLOUD TRACK WINDS AND SOUNDING DATA ACROSS JAPAN, THE STRONG MID- TO UPPER-LEVEL WEST-SOUTHWESTERLY FLOW REMAINS ENTRENCHED ACROSS, AND JUST SOUTH OF JAPAN (E.G., HACHIYO JIMA SOUNDING). THE CHICHI JIMA SOUNDING INDICATES DEEP SOUTHWESTERLIES AND CONTINUES TO SUPPORT THIS FORECAST TRACK. TS 13W IS EXPECTED TO TRACK ALONG THE LOW- TO MID-LEVEL SUBTROPICAL RIDGE POSITIONED TO THE EAST AND SOUTHEAST AND WILL TURN NORTHEASTWARD AND ACCELERATE WITHIN THE STRONG MIDLATITUDE WESTERLIES. WITH THE EXCEPTION OF NOGAPS AND GFDN (THROUGH TAU 36), THE MODELS SUPPORT THIS TRACK WITH A TIGHT CLUSTER OF MODEL VORTEX TRACKERS. BOTH NOGAPS AND GFDN HAVE EXHIBITED AN ERRONEOUS, EARLY NORTHWESTWARD BIAS OVER THE PAST 36 HOURS--THIS HAS YET TO VERIFY AND THE UPPER AIR DATA PREVIOUSLY MENTIONED DOES NOT SUPPORT IT. RELIABLE INTENSITY GUIDANCE CONTINUES TO INDICATE A PEAK INTENSITY BETWEEN 60-70 KNOTS AT TAU 36-48 BASED ON IMPROVED POLEWARD OUTFLOW. TS 13W IS STILL EXPECTED TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 48 AND COMPLETE BETWEEN TAU 72-96. C. TS 13W IS FORECAST TO COMPLETE ETT JUST AFTER TAU 72. THE MAJORITY OF THE MODELS CLEARLY INDICATE THAT THE SYSTEM WILL BE EMBEDDED WITHIN THE MIDLATITUDE WESTERLIES AT THAT TIME WITH AN OBVIOUS FRONTAL SIGNATURE IN THE 1000-500MB THICKNESS FIELDS.// NNNN