WDPN34 PGTW 130300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (USAGI) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.1N 127.7E INITIAL INTENSITY: 70 KTS GEOGRAPHIC REFERENCE: 390 NM EAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 29 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 27W (USAGI) WITH WELL-DEFINED CONVECTIVE BANDING TIGHTLY WRAPPING INTO AN OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). ENVIRONMENTAL ANALYSIS INDICATES THAT 27W IS IN A FAVORABLE ENVIRONMENT FOR INTENSIFICATION CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE TIGHTLY WRAPPING CLOUD LINES IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 70 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.0 - 65 KTS RJTD: T4.0 - 65 KTS RCTP: T4.0 - 65 KTS KNES: T4.0 - 65 KTS CIMSS SATCON: 67 KTS AT 130100Z CIMSS ADT: 51 KTS AT 130000Z CIMSS AIDT: 60 KTS AT 130000Z CIMSS DPRINT: 76 KTS AT 130000Z CIMSS DMINT: 78 KTS AT 122133Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: 27W IS FORECAST TO TRACK WEST-NORTHWESTWARD THROUGH TAU 36, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR TO THE NORTH. NEAR TAU 36, THE SYSTEM WILL BEGIN TO ROUND THE RIDGE AXIS AS IT ENTERS THE LUZON STRAIT. AFTER TAU 72, A BIFURCATION IN GUIDANCE STILL REMAINS WITH SOME MODELS SUGGESTING A SOUTHWESTWARD TRACK INTO THE SOUTH CHINA SEA AFTER TAU 48 WHILE OTHERS SUGGESTS A RECURVE. THE MAIN REASONING FOR THE TURN TO THE SOUTHWEST IS AN INCOMING COLD SURGE FLOWING SOUTHWESTWARD NEAR TAIWAN. THE VORTEX IS FORECAST TO BE STRONG ENOUGH TO NOT GET SHOVED BY THE SURGE AND CONTINUE WITH A RECURVE, BUT THERE COULD BE LARGE CHANGES TO THE FORECAST IF GUIDANCE SHIFTS. REGARDING INTENSITY, 27W IS FORECAST TO BEGIN QUICKLY INTENSIFYING OVER THE NEXT 36 HOURS TO A PEAK OF 100 KTS IN RESPONSE TO THE HIGHLY CONDUCIVE ENVIRONMENT. AFTER TAU 48, THE ENVIRONMENT WILL QUICKLY WORSEN DUE TO INCREASING VERTICAL WIND SHEAR AND COOLING SEA SURFACE TEMPERATURES. ADDITIONALLY, THE COLD SURGE BRINGING IN COLD AND DRY AIR WILL FURTHER AID IN WEAKENING THE SYSTEM. 27W IS FORECAST TO BEGIN EXTRATROPICAL TRANSITION NEAR TAU 96 WITH COMPLETION BY TAU 120. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 48, BUT THEN VERY QUICKLY DIVERGES DUE TO THE MENTIONED BIFURCATION. THE ECMWF ENSEMBLE CONTINUES TO HAVE NEAR 100 PERCENT OF MEMBERS RECURVING WHILE THE GFS ENSEMBLE IS SPLIT BETWEEN THE RECURVE AND THE SOUTHWESTWARD TRACK INTO THE SOUTH CHINA SEA. THE JTWC TRACK FORECAST HAS A RECURVE, IN LINE WITH THE ECMWF ENSEMBLE, AS WELL AS THE GALWEM, UKMET, AND COAMPS-TC TRACKERS. INTENSITY GUIDANCE IS NOW IN WORSE AGREEMENT WITH HAFS-A AND HWRF AGREEING ON RAPID INTENSIFICATION (RI) WHILE GFS SUGGESTS A STEADY INTENSITY. RAPID INTENSIFICATION AIDS HAVE NOW DISAPPEARED. THE COAMPS-TC ENSEMBLE ALSO SUGGESTS A VASTLY LOWER PROBABILITY OF RI AS WELL. ADDITIONALLY, THE TRACK INTO THE SOUTH CHINA SEA WOULD COMPLETELY CHANGE THE INTENSITY FORECAST AS WELL. OVERALL, THE JTWC INTENSITY FORECAST IS PLACED CLOSER TO THE HAFS-A AND HWRF WITH LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN