WDPN31 PGTW 211500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (TEN) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.0N 126.3E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 338 NM EAST-NORTHEAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DISPLACED TO THE NORTHEAST OF AN AREA OF SYMMETRICAL FLARING CONVECTION. A 211224Z ASCAT-B PARTIAL SCATTEROMETER PASS SHOWED THE TIGHT, WELL-DEFINED LLCC TO THE NORTHEAST OF THE CONVECTION, AND A FAIRLY LARGE WIND FIELD WITH 25 KNOT WINDS EXTENDING ABOUT 100 NM TO THE NORTH AND SOUTH OF THE CENTER. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SCATTEROMETER DATA AND THE EXPOSED LLCC IN THE EIR. THE INITIAL INTENSITY IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON THE SCATTEROMETER WIND SPEED DATA AND IS IN LINE WITH THE SUBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES OF T1.5 FROM PGTW, RJTD AND KNES. WHILE TD 10W HAS NOT BEEN ABLE TO CONVECTIVELY ORGANIZE, THE WINDS AROUND THE SYSTEM HAVE STEADILY INCREASED AS THE PRESSURE HAS CONTINUED TO FALL. THE ENVIRONMENT IS MARGINALLY FAVORABLE CURRENTLY, WITH MODERATE (15-20 KNOTS) NORTHEASTERLY WIND SHEAR OFFSET SOMEWHAT BY STRONG EQUATORWARD DIFFLUENT OUTFLOW AND VERY WARM (30-31C) SSTS AND HIGH OHC. THE SYSTEM IS MOVING SLOWLY ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH. WIND RADII BASIS: THERE ARE NO WIND RADII IN THE ANALYSIS. CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.5 - 25 KTS KNES: T1.5 - 25 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE EQUATORWARD OTHER FACTORS: HIGH OHC ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NA 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES. THIS IS THE FIRST WARNING AND ESTABLISHES THE FORECAST REASONING. FORECAST DISCUSSION: TD 10W HAS SLOWLY BUT STEADILY INTENSIFIED OVER THE PAST COUPLE OF DAYS, EVEN THOUGH IT HAS BEEN UNABLE TO ESTABLISH A CONVECTIVE STRUCTURE TYPICAL OF A TROPICAL CYCLONE AND RECENT SCATTEROMETER DATA PROVES THE WIND FIELD HAS REACHED 25 TO 30 KNOTS. OVER THE NEXT 24 HOURS THE SYSTEM WILL TRACK GENERALLY TOWARDS THE WEST, WITH A BIT OF A WEST-SOUTHWEST JOG IN THE NEAR-TERM AS IT MOVES ALONG THE SOUTHERN SIDE OF A DEEP STR TO THE NORTH. AFTER TAU 24 THE SYSTEM IS EXPECTED TO TURN ONTO A MORE NORTHWESTWARD TRACK AS THE RIDGE BEGINS TO STRENGTHEN AND BUILD TO THE EAST, WITH THE CENTER EVENTUALLY ASSUMING A POSITION TO THE EAST OF TD 10W. TD 10W IS FORECAST TO SKIRT THE NORTHEAST TIP OF LUZON AROUND TAU 36, THEN TRACK NORTHWESTWARD TOWARDS A LANDFALL NEAR HONG KONG AROUND TAU 96. DUE TO THE RELATIVELY HIGH SHEAR AND THE LACK OF A CONVECTIVE CORE STRUCTURE, TD 10W WILL STRUGGLE TO INTENSIFY MUCH IN THE NEAR-TERM, WITH THE FORECAST CALLING FOR SLOW BUT STEADY INTENSIFICATION TO TROPICAL STORM STRENGTH BY TAU 36. ONCE PAS LUZON THE SYSTEM WILL INTENSIFY A BIT MORE RAPIDLY AS THE MODEL GUIDANCE SUGGESTS A WEAK POINT SOURCE MAY DEVELOP OVER THE SYSTEM, FINALLY ALLOWING FOR A BURST OF INTENSIFICATION PRIOR TO LANDFALL ALONG THE CHINESE COAST. ONCE ASHORE IN SOUTHEAST CHINA, TD 10W WILL RAPIDLY WEAKEN AND ULTIMATELY DISSIPATE NO LATER THAN TAU 120. MODEL DISCUSSION: DUE TO TECHNICAL ISSUES AT JTWC, RELIABLE DETERMINISTIC MODEL TRACKERS ARE NOT CURRENTLY AVAILABLE AND THUS THE TRACK FORECAST IS GENERATED USING GLOBAL MODEL FIELD ANALYSIS. GENERALLY SPEAKING THE GFS, ECMWF AND NAVGEM MODELS CONCUR IN THE OVERALL TRACK, WITH ONLY MODEST SPREAD THROUGH TAU 72, INCREASING THROUGH THE END OF THE FORECAST. ALL THREE MODELS AGREE THAT TD 10W WILL SKIRT THE NORTHEAST TIP OF LUZON, WITH THE GFS BEING THE FURTHEST SOUTH OF THE BUNCH. IN THE LONGER TERM, THE GFS REMAINS THE SOUTHERN OUTLIER TAKING THE SYSTEM TO A LANDFALL SOUTH OF HONG KONG, WHILE THE NAVGEM AND ECMWF TAKE THE SYSTEM ASHORE TO THE NORTH OF HONG KONG. THE ENSEMBLE GUIDANCE SHOWS A MUCH WIDER SPREAD, BETWEEN NORTHERN HAINAN AND SOUTHERN TAIWAN. THE JTWC FORECAST LIES CLOSE TO THE ECMWF SOLUTION WITH LOW CONFIDENCE. INTENSITY GUIDANCE IS ALSO EXTREMELY LIMITED, WITH ONLY COAMPS-TC AVAILABLE AND SHOWING A PEAK OF 75-80 KNOTS. BASED ON THE UPPER-LEVEL ENVIRONMENT FORECAST BY THE GLOBAL MODELS, THE JTWC FORECAST IS LOWER THE AGGRESSIVE COAMPS-TC, BUT CONFIDENCE IS LOW BASED ON A LACK OF RELIABLE GUIDANCE AT THIS TIME. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN