WDPN33 PGTW 232100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (CO-MAY) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.9N 118.0E INITIAL INTENSITY: 60 KTS GEOGRAPHIC REFERENCE: 221 NM NORTHWEST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 27 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL STORM (TS) 11W IS EMBEDDED WITHIN THE SOUTHWESTERN EDGE OF A LARGE CYCLONIC GYRE ROTATION, WHICH EXTENDS ACROSS APPROXIMATELY 1000NM, FROM TS 11W ALL THE WAY NORTHEASTWARD TO AND BEYOND TS 10W. THE CENTROID OR AXIS OF ROTATION OF THIS GYRE PATTERN IS CURRENTLY POSITIONED IN THE PHILIPPINE SEA TO THE EAST OF THE LUZON STRAIT, AND ANIMATED TOTAL PERCEPTIBLE WATER (TPW) IMAGERY SHOWS MULTIPLE TROPICAL SYSTEMS ROTATING ABOUT THIS CENTROID. AS DEPICTED IN THE ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY, TS 11W IS CURRENTLY UNDERGOING RAPID INTENSIFICATION (RI), UNDER VERY FAVORABLE ENVIRONMENTAL CONDITIONS. THE EIR SHOWS EXTREMELY DEEP CONVECTION, WITH VERY COLD OVERSHOOTING CLOUD TOPS DEVELOPING IN CLOSE PROXIMITY TO THE ASSESSED CENTER. HOWEVER, CONVECTION HAS YET TO FULLY SYMMETRIZE AND AN EYE HAS YET TO APPEAR IN THE EIR. HOWEVER, A 231529Z WSF-M COLOR-ENHANCED 37GHZ MICROWAVE IMAGE REVEALED A STRONG LOW-LEVEL MICROWAVE EYE FEATURE, WITH A SYMMETRICAL CYAN RING, INDICATIVE OF NEAR-TERM RI. ADDITIONALLY, A 231748Z AMSR2 COLOR-ENHANCED 89GHZ IMAGE REVEALED A VERTICALLY ALIGNED, SYMMETRICAL MICROWAVE EYE WITH STRONG CONVECTIVE BANDS WRAPPING INTO THE CENTER. THE MICROWAVE IMAGES PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, HIGHER THAN AVAILABLE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES, HEDGED HIGHER DUE TO THE FACT THAT DVORAK-BASED TECHNIQUES HISTORICALLY UNDERPERFORM ON COMPACT SYSTEMS. THE ENVIRONMENT IS HIGHLY FAVORABLE WITH LOW SHEAR, VERY WARM SSTS AND STRONG DUAL-CHANNEL OUTFLOW, PROVIDING OUTSTANDING SUPPORT FOR ADDITIONAL RI. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: THE SYSTEM IS TRACKING ALONG THE GRADIENT FLOW BETWEEN A LARGE CYCLONIC GYRE WITH A CENTROID OVER THE PHILIPPINE SEA AND A NEAR EQUATORIAL RIDGE (NER) OVER THE MALAY PENINSULA. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS KNES: T3.5 - 55 KTS DEMS: T3.5 - 55 KTS CIMSS SATCON: 44 KTS AT 231900Z CIMSS ADT: 51 KTS AT 231730Z CIMSS AIDT: 42 KTS AT 231730Z CIMSS D-MINT: 34 KTS AT 231757Z CIMSS D-PRINT: 42 KTS AT 231730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG DUAL-CHANNEL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE ENDPOINT OF THE FORECAST HAS BEEN EXTENDED DOWN TRACK BY ABOUT 160NM SINCE THE PREVIOUS RUN. RAPID INTENSIFICATION (RI) HAS BEEN SPECIFICALLY INTRODUCED WITH THIS FORECAST AND AN ALTERNATE SCENARIO HAS BEEN ADDED TO THE FORECAST DISCUSSION. FORECAST DISCUSSION: TS 11W HAS TRACKED SOUTHWESTWARD OVER THE PAST SIX HOURS, PUSHING FURTHER AWAY FROM THE LUZON COASTLINE THAN ORIGINALLY EXPECTED. THERE IS NO CHANGE TO THE OVERALL STEERING PATTERN, AND TS 11W WILL TURN SOUTHWARD IN THE NEXT FEW HOURS AS IT CONTINUES TO TRACK ALONG THE GRADIENT BETWEEN THE LARGE CYCLONIC GYRE TO THE NORTHEAST AND THE NER TO THE SOUTHWEST. BY TAU 12, THE SYSTEM WILL HAVE REACHED THE INFLECTION POINT IN THE SOUTHWESTERN TIP OF THE GYRE, AND THEN WILL RAPIDLY TURN NORTHEASTWARD THROUGH TAU 18. BY TAU 24, THE SYSTEM WILL HAVE ACCELERATED VERY QUICKLY TO THE NORTHEAST AS THE PRIMARY STEERING INFLUENCE SHIFTS TO THE TIGHT GRADIENT BETWEEN THE EAST SIDE OF THE GYRE AND A STRONG STR NORTHWEST OF GUAM. THE SYSTEM IS FORECAST TO LIE JUST WEST OF VIGAN, PHILIPPINES BY TAU 24, WITH A LANDFALL EXPECTED ALONG THE NORTHWESTERN TIP OF LUZON OCCURRING SHORTLY AFTER TAU 24. THE SYSTEM THEN CONTINUES ACCELERATING NORTHEASTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD. DUE TO THE HIGHLY FAVORABLE ENVIRONMENT, TS 11W IS FORECAST TO RI OVER THE NEXT 24 HOURS, REACHING PEAK INTENSITY OF AT LEAST 85 KNOTS JUST PRIOR TO LANDFALL. THE CURRENT FORECAST CALLS FOR THE SYSTEM TO TRACK OVER THE RUGGED TERRAIN OF NORTHWEST LUZON, WHICH COMBINED WITH INCREASING EASTERLY SHEAR, RAPIDLY WEAKEN THE SYSTEM THROUGH THE END OF THE FORECAST. MOST GLOBAL MODELS INDICATE THE SYSTEM WILL OPEN UP INTO A TROUGH AS IT RAPIDLY WEAKENS, WITH 25-30 KNOT SOUTHERLY FLOW ON THE EASTERN PERIPHERY, WITH THE SYSTEM DISSIPATING AS A TROPICAL CYCLONE BY TAU 48. AN ALTERNATE SCENARIO FINDS THE SYSTEM CONTINUING A SOUTHWESTWARD TRACK FOR A BIT LONGER, OPENING THE DISTANCE TO LUZON EVEN MORE, SUCH THAT THE CENTER AND INNER-CORE REMAIN OFFSHORE THROUGHOUT THE FORECAST. THIS WILL RESULT IN A MUCH STRONGER SYSTEM MOVING INTO THE LUZON STRAIT. SHEAR WILL STILL TAKE ITS TOLL IN THE ALTERNATE SCENARIO, HOWEVER IN THIS SCENARIO, THE RAPIDLY WEAKENING SYSTEM WILL PUSH FURTHER NORTHEAST TOWARDS THE RYUKUS AS A STRONGER TROPICAL STORM BEFORE DISSIPATING. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD CROSS-TRACK AGREEMENT THROUGH TAU 36, WITH 65NM OF SPREAD AT TAU 36, WITH THE CONSENSUS MEAN LYING JUST BARELY INLAND ON THE NORTHWEST TIP OF LUZON. ALONG-TRACK SPREAD INCREASES SHARPLY BEGINNING AT TAU 24, AND INCREASES TO 250NM BY TAU 36 BETWEEN THE VERY FAST EC-AIFS AND THE LAGGING NAVGEM. BY TAU 48, BOTH CROSS- AND ALONG-TRACK UNCERTAINTY INCREASES SHARPLY AGAIN, UP TO 330NM AND 225NM RESPECTIVELY. THE JTWC FORECAST IS POSITIONED CLOSE TO THE ECMWF AND ECENS MEAN THROUGH THE FORECAST PERIOD. THE BULK OF THE MESOSCALE INTENSITY MODELS ARE NOT IMPRESSED WITH TS 11W AND DEPICT LITTLE IN THE WAY OF INTENSIFICATION OVER THE NEXT 24 HOURS. MEANWHILE, NEARLY EVERY RI AID AVAILABLE HAS BEEN TRIPPED, AND EVEN THE DECAY-SHIPS MEMBERS SUPPORT NEAR-TERM RI. THUS THE JTWC FORECAST DEVIATES SIGNIFICANTLY HIGHER THAN MOST OF THE INTENSITY GUIDANCE BUT IS CONSISTENT WITH THE SHIPS OUTPUT AND THE RI AIDS. SOME RI AIDS SUPPORT AN EVEN HIGHER PEAK INTENSITY NEAR 100 KNOTS AND THIS CANNOT BE RULED OUT JUST YET, ESPECIALLY IF THE SYSTEM REMAINS FURTHER OFFSHORE. THE JTWC FORECAST ALSO DEVIATES LOWER THAN MOST OF THE GUIDANCE AT THE END OF THE FORECAST, TO INDICATE VERY RAPID WEAKENING OF THE SYSTEM AS DEPICTED IN THE BULK OF THE GLOBAL AND MESOSCALE MODELS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN