WDPN33 PGTW 112100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KOMPASU) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 18.8N 120.5E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 254 NM NORTH OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: OVER THE PAST SIX HOURS, THE SMALL INNER CORE OF OTHERWISE VERY LARGE TS KOMPASU, HAS SKIRTED THE FAR NORTHERN TIP OF LUZON, AND IS NOW MOVING INTO THE SOUTH CHINA SEA. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS EXTENSIVE OUTER CONVECTIVE BANDS, EXTENDING FROM NORTH OF TAIWAN SOUTH TO THE NORTHERN SULU SEA, WRAPPING INTO A SOMEWHAT DISORGANIZED LOW LEVEL CIRCULATION CENTER (LLCC). THE PASSAGE OF TS KOMPASU CLOSE TO THE RUGGED TERRAIN OF LUZON HAS DISRUPTED THE INFLOW INTO THE CORE, AND THUS THE OVERALL SATELLITE DEPICTION HAS DEGRADED OVER THE PAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE JUST OFF THE NORTHWEST TIP OF LUZON BASED ON ANIMATED RADAR DATA FROM PAGASA, AND SURFACE WIND OBSERVATIONS FROM LAOAG, APARRI AND CALAYAN, PHILIPPINES. THE INITIAL INTENSITY OF 55 KNOTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A CONGRUENCE OF AGENCY FIXES AT T3.5, IN AGREEMENT WITH THE CIMSS ADT ESTIMATE, AND A SEA LEVEL PRESSURE READING OF 980MB FROM LAOAG, WHICH SUPPORTS A 55 KNOT INTENSITY BASED ON THE WIND-PRESSURE RELATIONSHIP. THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE WITH WARM SSTS, MODERATE LEVELS OF VERTICAL WIND SHEAR (VWS) ALONG WITH STRONG EQUATORWARD AND MODERATE POLEWARD OUTFLOW ALOFT. INITIAL WIND RADII BASIS: SCATTEROMETER DATA. CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T3.5 - 55 KTS RCTP: T3.5 - 55 KTS KNES: T3.5 - 55 KTS CIMSS ADT: 57 KTS AT 111740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: LAND INTERACTION WITH LUZON. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS KOMPASU IS FORECAST TO CONTINUE TRACKING WESTWARD THROUGH THE FORECAST PERIOD UNDER THE INFLUENCE OF DEEP-LAYER STR ENTRENCHED OVER CENTRAL CHINA. THE SYSTEM IS FORECAST TO CROSS OVER HAINAN ISLAND BY TAU 48, CROSS INTO THE GULF OF TONKIN, AND MAKE A SECOND LANDFALL IN NORTHERN VIETNAM SHORTLY AFTER TAU 72. THE SYSTEM HAS ANOTHER 12 TO 18 HOURS OF GOOD ENVIRONMENTAL CONDITIONS, AND NOW THAT IT IS MOVING AWAY FROM LUZON, ONCE THE INNER CORE IS REESTABLISHED, SHOULD INTENSIFY TO A PEAK OF 60 KNOTS BY TAU 12. THEREAFTER VWS IS FORECAST TO STEADILY INCREASE, WHICH WILL LEAD TO A SLOW WEAKENING TREND. ONCE ASHORE OVER HAINAN, THE SYSTEM WILL WEAKEN DRAMATICALLY, BUT IS FORECAST TO REMAIN AT MINIMAL TROPICAL STORM STRENGTH AS IT CROSSES OVER HAINAN. THE COMBINATION OF REDUCED OUTFLOW ALOFT, AND MODERATE SHEAR LEVELS WILL PRECLUDE INTENSIFICATION IN THE GULF OF TONKIN. AFTER LANDFALL, THE SYSTEM RUGGED TERRAIN OF NORTHERN VIETNAM WILL RAPIDLY ERODE THE SYSTEM, LEADING TO FULL DISSIPATION NO LATER THAN TAU 120 OVER LAOS. MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT, WITH A 95NM SPREAD AT TAU 48 AS THE SYSTEM TRACKS OVER HAINAN, INCREASING TO 140NM BY TAU 96 OVER VIETNAM. THE JTWC TRACK LIES CLOSE TO, BUT SLIGHTLY SLOWER THAN, THE CONSENSUS MEAN WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT, WITH THE MESOSCALE MODELS INDICATING NEAR-TERM INTENSIFICATION FOLLOWED BY STEADY WEAKENING FOR THE REMAINDER OF THE FORECAST. THE JTWC FORECAST IS ABOVE THE CONSENSUS MEAN, TRACKING THE COAMPS-TC THROUGH TAU 24, THEN DIVES WELL BELOW THE MEAN AS THE SYSTEM MOVES OVER HAINAN, THEN NEAR THE MEAN THROUGH THE REMAINDER OF THE FORECAST. CONFIDENCE IS MEDIUM THROUGH LANDFALL ON HAINAN, DECREASING TO LOW THEREAFTER. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN