WDPN32 PGTW 172100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (MAN-YI) WARNING NR 036// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.7N 119.4E INITIAL INTENSITY: 75 KTS GEOGRAPHIC REFERENCE: 208 NM NORTH-NORTHWEST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 17 KTS SIGNIFICANT WAVE HEIGHT: 24 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON 25W (MAN-YI) WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) AND FRAGMENTED CONVECTIVE BANDING ALONG THE SOUTHERN AND EASTERN PERIPHERIES OF THE CIRCULATION. THE WESTERN PORTION OF THE SYSTEM IS VOID OF CONVECTION, BUT THE LLCC SEEMS TO STILL BE STRONG. ENVIRONMENTAL ANALYSIS INDICATES THAT 25W IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE RADIAL OUTFLOW ALOFT, LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR, AND WARM (28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 75 KTS IS ASSESSED WITH LOW CONFIDENCE DUE TO THE SHORT TIME BACK OVER WATER. AGENCY DVORAK FINAL T NUMBERS AND OBJECTIVE INTENSITY ESTIMATES SUGGEST AN INTENSITY OF AROUND 70-75 KTS THOUGH. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF AN EXTENSION OF A SUBTROPICAL RIDGE (STR) TO THE EAST THAT EXTENDS WESTWARD, NORTH OF THE SYSTEM. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.5 - 77 KTS RJTD: T5.5 - 102 KTS RCTP: T5.0 - 90 KTS KNES: T6.0 - 115 KTS DEMS: T4.5 - 77 KTS CIMSS SATCON: 77 KTS AT 171700Z CIMSS ADT: 94 KTS AT 171800Z CIMSS AIDT:71 KTS AT 171800Z CIMSS DMINT: 83 KTS AT 171800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: PRESSURE FROM THE COLD SURGE FLOWING SOUTHWESTWARD INTO THE SOUTH CHINA SEA. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: 25W IS FORECAST TO TRACK WEST-NORTHWESTWARD, ALONG THE SOUTHERN PERIPHERY OF THE RIDGING TO THE NORTH THROUGH TAU 24. THE COLD SURGE FLOWING INTO THE SOUTH CHINA SEA ALONG WITH THE MENTIONED RIDGING WILL INHIBIT 25W FROM GAINING MUCH LATITUDE. FROM TAU 24 TO 48, 25W IS FORECAST TO TRACK GENERALLY WESTWARD TOWARD HAINAN. AFTER TAU 48, THE WEAKENED VORTEX IS FORECAST TO TRACK ALONG THE LOW-LEVEL STEERING PATTERN AS IT DISSIPATES NEAR TAU 72. REGARDING INTENSITY, 25W IS FORECAST TO WEAKEN STEADILY THROUGH TAU 48 TO AROUND 35 KTS IN RESPONSE TO A MARGINAL ENVIRONMENT (25-30 KTS OF SHEAR AND COOLER SEA SURFACE TEMPERATURES). ADDITIONALLY, THE COLD SURGE WILL BRING IN COLD, DRY AIR WHICH WILL AID IN WEAKENING THE SYSTEM. AFTER TAU 48, THE ENVIRONMENT QUICKLY WORSENS WITH AROUND 35 KTS OF SHEAR AND SIGNIFICANT DRY AIR ENTRAINMENT. AS A RESULT, 25W IS FORECAST TO DISSIPATE SOUTH OF HAINAN AROUND TAU 72. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT REGARDING THE TRACK OF 25W THROUGH TAU 48 WITH A 110 NM CROSS-TRACK SPREAD AT THAT TIME. AFTER TAU 48 THE MODELS BEGIN TO DIVERGE AS THE VORTEX WEAKENS. GALWEM IS A PRIMARY OUTLIER, TRACKING THE VORTEX INTO SOUTHERN VIETNAM AT TAU 72. THE JTWC TRACK FORECAST IS PLACED CLOSE TO CONSENSUS, DISREGARDING GALWEM, WITH OVERALL MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH ALL MODELS SUGGESTING WEAKENING THROUGH THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO CONSENSUS THROUGHOUT THE FORECAST WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN