WDPN33 PGTW 291500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (HAIKUI) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.1N 137.2E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 411 NM SOUTHWEST OF IWO TO MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) AND PROXY VISIBLE SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) TO THE EAST OF AN AREA OF PERSISTENT CONVECTION WITH ROBUST OVERSHOOTING TOPS. WHILE THE CONVECTION IS IMPRESSIVE, BASED ON THE PROXY VISIBLE IMAGERY AND A 290918Z SSMIS 91GHZ IMAGE AND A 291202Z AMSU-B 89GHZ IMAGE, THE VORTEX IS SIGNIFICANTLY TILTED TO THE WEST WITH HEIGHT DUE TO PERSISTENT MODERATE EASTERLY SHEAR. THIS IS BORN OUT IN HAFS-A CROSS SECTIONS WHICH SHOW AN EXTREMELY TILTED VORTEX. THE LATEST IMAGERY SHOWS CONVECTION IS PUSHING EAST AGAINST THE SHEAR, AND THE LLCC IS TUCKING BACK UNDER THE EASTERN PORTION OF THE CDO FEATURE, BUT IT REMAINS TO BE SEEN IF THIS PUSH WILL SUSTAIN ITSELF. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE LLCC EVIDENT IN THE IMAGERY DESCRIBED ABOVE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON EVALUATION OF THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES AVERAGING T3.5 AND THE SUBJECTIVE ESTIMATES AVERAGING ROUGHLY 55 KNOTS. THE SYSTEM IS TRACKING WESTWARD ALONG THE SOUTHERN SIDE OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH. ENVIRONMENTAL ANALYSIS REVEALS ROUGHLY FAVORABLE CONDITIONS, WITH WARM SSTS AND GOOD WESTWARD AND EQUATORWARD OUTFLOW OFFSET BY THE MODERATE EASTERLY SHEAR. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T4.0 - 65 KTS RCTP: T3.0 - 45 KTS KNES: T3.0 - 45 KTS CIMSS ADT: 47 KTS AT 291140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE FORECAST POINTS IN THE LATER PORTIONS IN THE FORECAST HAVE BEEN SHIFTED 150NM SOUTHWARD AS TRACK UNCERTAINTY CONTINUES TO INCREASE. FORECAST DISCUSSION: A REANALYSIS OF EARLIER MICROWAVE IMAGERY HAS RESULTED IN A SLOWING IN THE TRACK SPEED, BUT NO MAJOR SHIFT IN THE TRACK DIRECTION, WITH TROPICAL STORM (TS) 09W (HAIKUI) STILL HEADING TOWARDS THE WEST-NORTHWEST ALONG THE SOUTHERN SIDE OF THE STRONG STR FAR TO THE NORTHEAST. CONTINUING THE TREND ESTABLISHED SIX HOURS AGO, MODEL GUIDANCE CONTINUES TO DIVERGE AT A STEADILY INCREASING RATE, WITH THE DIVERGENCE BEGINNING AS EARLY AS TAU 36. THE KEY DIFFERENCE FROM SIX HOURS AGO IS THAT THE ECMWF AND ITS ENSEMBLE ARE NOW THE SOLE OUTLIERS IN TAKING THE SYSTEM ON A PATH STRAIGHT AT OKINAWA AND ONWARDS INTO THE EAST CHINA SEA. THE REMAINDER OF THE GUIDANCE IS TRENDING CLOSER TO THE GFS-BASED FAMILY OF MODELS WHICH INSIST THE SYSTEM WILL TURN SHARPLY SOUTHWEST AFTER TAU 36, PERFORM A COUNTER-CLOCKWISE LOOP, AND THEN TRACK BACK TO THE NORTHEAST UNDER THE INFLUENCE OF A STRENGTHENING RIDGE OVER EASTERN CHINA, AND A BINARY INTERACTION WITH A POTENTIAL FUTURE TROPICAL CYCLONE DEVELOPING EAST OF GUAM. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND THE CONSENSUS MEAN TO TAU 48, THEN DEPARTS FROM THE MEAN, HEDGING TOWARDS THE SOUTH AND WEST NEAR THE GFS ENSEMBLE MEAN. ENSEMBLE SPREAD IS LESS THAN IT WAS EARLIER, WITH ONLY A HANDFUL OF GEFS MEMBERS SUPPORTING THE NORTHERN TRACK. BUT THE 1000NM SPREAD BETWEEN THE GFS AND ECMWF TRACKERS AT TAU 120 ARE INDICATIVE OF THE EXTREME UNCERTAINTY IN THE FORECAST TRACK. HAVING BRIEFLY POKED ITS HEAD OUT OF FROM UNDER THE CONVECTIVE MASS EARLIER IN THE DAY, THE LLCC HAS DECIDED ITS HAD ENOUGH MOON SHINE FOR ONE NIGHT AND TUCKED BACK UNDER THE CONVECTIVE SHIELD IN THE PAST COUPLE OF HOURS. DUE TO THE PRESENCE OF PERSISTENT MODERATE EASTERLY SHEAR, IT REMAINS TO BE SEEN IF THE CONVECTIVE TOWERS CURRENTLY FIRING ON THE UPSHEAR SIDE CAN ACTUALLY CONTINUE FOR MORE THAN A BRIEF PERIOD OF TIME. SHEAR IS EXPECTED TO REMAIN AT MODERATE LEVELS FOR THE NEXT 24 HOURS OR SO AND WILL PUT A BRAKE ON VORTEX ALIGNMENT AND INTENSIFICATION. SHEAR IS EXPECTED TO RELAX SOMEWHAT AFTER TAU 24, ALLOWING THE SYSTEM TO SYMMETRIZE AND INTENSIFY AT A FASTER RATE, REACHING A PEAK OF 95 KNOTS BY TAU 72. HOWEVER, DUE TO THE EXTREME UNCERTAINTY IN THE TRACK, THE INTENSITY GUIDANCE IS ALSO HIGHLY UNCERTAIN DUE TO THE RELATIONSHIP BETWEEN THE TRACK AND INTENSITY. A TRACK MORE IN LINE WITH THE GFS WILL RESULT IN A MUCH HIGHER INTENSITY PEAK, WHILE AN ECMWF-LIKE TRACK WILL LEAD TO A LOWER PEAK. MODEL DISCUSSION: AS DISCUSSED ABOVE, DETERMINISTIC TRACK GUIDANCE EXHIBITS AND UNUSUALLY LARGE SPREAD OF NEAR 1000NM AT TAU 120, WHILE ENSEMBLE MEMBER SHOW A SIMILARLY WIDE SPREAD. THE JTWC TRACK LIES CLOSE TO THE CONSENSUS MEAN TO TAU 48, THEN IS SIGNIFICANTLY SLOWER AND TO THE SOUTH OF THE MEAN THROUGH THE REMAINDER OF THE FORECAST, MOST CLOSELY TRACKING THE GFS ENSEMBLE MEAN. CONFIDENCE IS VERY LOW THROUGH THE ENTIRE FORECAST PERIOD AND MAJOR SHIFTS IN THE TRACK CAN BE EXPECTED IN FUTURE FORECASTS AS THE STEERING PATTERN CONTINUES TO EVOLVE. INTENSITY GUIDANCE IS VERY MIXED AS WELL, WITH THE COAMPS-TC (BOTH VERSIONS) AND THE ENSEMBLE MEAN INDICATING RAPID INTENSIFICATION (RI) AFTER TAU 24, TO A PEAK NEAR 150 KNOTS. HOWEVER, IN LIGHT OF THE FACT THAT THE COAMPS-TC TRACK IS CLOSE TO THE GFS DETERMINISTIC, IT IS CURRENTLY ASSESSED AS UNLIKELY. THE JTWC FORECAST LIES ON TOP OF THE CONSENSUS MEAN WITH LOW CONFIDENCE, AND MAJOR CHANGES IN THE TRACK FORECAST WILL RESULT IN LARGE SHIFTS IN THE INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN