MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (YUTU) WARNING NR 16// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON 31W (YUTU), LOCATED APPROXIMATELY 151 NM WEST- NORTHWEST OF TINIAN, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS STY 31W HAS MAINTAINED A WELL-DEFINED EYE WITH DEEP CONVECTION SURROUNDING IT. THE INITIAL POSITION IS BASED ON A 250600Z HIMAWARI VISIBLE SATELLITE IMAGE WHICH SHOWS THE 15NM WIDE EYE. THE INITIAL INTENSITY IS MAINTAINED AT 145 KNOTS, BETWEEN THE DVORAK CURRENT INTENSITY (CI) ESTIMATES OF T7.5 (155 KNOTS) FROM RJTD AND KNES AND A T7.0 (140 KTS) ESTIMATE FROM PGTW, AND SLIGHTLY ABOVE THE 250651Z SATCON ESTIMATE OF 140 KTS. STY 31W HAS BEEN UNDERGOING AN EYEWALL REPLACEMENT CYCLE (ERC), THOUGH A LACK OF RECENT HIGH RESOLUTION MICROWAVE IMAGERY MAKES IT DIFFICULT TO DETERMINE WHAT STAGE OF THE ERC STY 31W IS EXPERIENCING. ENVIRONMENTAL ANALYSIS SHOWS STY 31W IS MOVING INTO AN AREA OF MODERATE (15 TO 20 KTS) VERTICAL WIND SHEAR (VWS) AND HAS NEAR RADIAL OUTFLOW. SEA SURFACE TEMPERATURES ALSO REMAIN FAVORABLE, NEAR 30 DEGREES CELSIUS. STY 31W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST AND THE SOUTHEASTERN PERIPHERY OF AN STR LOCATED TO THE NORTHWEST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE JTWC FORECAST TRACK IS CURRENTLY STRAIGHT-RUNNING WEST-NORTHWESTWARD THROUGH TAU 120, BUT DOES NOT PRECLUDE THE POSSIBILITY OF A RECURVE AFTER TAU 120. B. THROUGH TAU 72, STY 31W WILL CONTINUE TO TRACK TO THE WEST- NORTHWEST WHILE POSITIONED BETWEEN THE AFOREMENTIONED STRS. MODEL GUIDANCE REMAINS IN FAIRLY GOOD AGREEMENT THOUGH TAU 24, INDICATING A WEST-NORTHWESTWARD TRACK, BUT QUICKLY DIVERGES AFTER THAT WITH A SPREAD OF 295 NM BY TAU 72. AT TAU 72, JGSM, GALWEM, AND THE UKMET MODEL ARE THE SOUTHERN OUTLIERS DEPICTING A STRAIGHT-RUNNING TRACK TO THE WEST, WHILE NAVGEM, COAMPS-NAVGEM, AND COAMPS-GFS ARE THE NORTHERN OUTLIERS DEPICTING A RECURVE SCENARIO BEGINNING AT TAU 72. GFS, HWRF, AND ECMWF ARE IN THE MIDDLE OF THIS TRIFURCATION SCENARIO SHOWING A WEST-NORTHWESTWARD TRACK THROUGH TAU 72. THE JTWC FORECAST TRACK IS PLACED NEAR THE MULTI-MODEL CONSENSUS IN THE MIDDLE OF THE TRIFURCATION SCENARIO. AS STY 31W ENTERS A REGION OF HIGHER VWS, IT WILL BEGIN A GRADUAL WEAKENING TREND, THOUGH SHORT- TERM INTENSIFICATION IS ALSO POSSIBLE AS THE ERC IS COMPLETED AND THE NEW, BROADER EYEWALL CONTRACTS. DUE TO THE WIDE SPREAD IN MODEL GUIDANCE THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK. C. BEYOND TAU 72, THE TRIFURCATION IN THE MODELS BECOMES EVEN MORE PRONOUNCED. NAVGEM, COAMPS-NAVGEM, AND COAMPS-GFS SHARPLY RECURVE THE SYSTEM AFTER TAU 72 AS A TROUGH MOVES THROUGH THE AREA AND SPLITS THE TWO STRS. JGSM, GALWEM, AND THE UKMET MODEL MAINTAIN STRONG STRS AND CONTINUE MOVING STY 31W TO THE WEST OVER LUZON. THE MIDDLE GROUP OF GFS, ECMWF, AND HWRF PREDICT A SLOWING TRACK SPEED TOWARDS THE END OF THE FORECAST PERIOD. NOTABLY, THE MOST RECENT RUNS OF ECMWF AND HWRF DO NOT DEPICT A RECURVE SCENARIO, THOUGH GFS NEWLY SHOWS A RECURVE SCENARIO STARTING AT THE END OF THE FORECAST PERIOD, MUCH FURTHER TO THE WEST THAN THE OTHER RECURVING MODELS, WHEN IT PREVIOUSLY PREDICTED A STRAIGHT-RUNNING SYSTEM. THE JTWC FORECAST TRACK IS PLACED NEAR THE MULTI-MODEL CONSENSUS, THOUGH IT HAS BEEN SHIFTED TO THE SOUTHWEST DUE TO ECMWF SHIFTING THE TRACK TO THE SOUTHWEST. STY 31W WILL CONTINUE TO WEAKEN GRADUALLY UNDER THE INCREASING VWS AND DRIER AIR IN THE PHILIPPINE SEA, ALTHOUGH SSTS WILL REMAIN FAVORABLE, ABOVE 28 CELSIUS. THE JTWC INTENSITY FORECAST IS PLACED WITH LOW CONFIDENCE ON THE HIGH SIDE OF THE MULTIMODEL CONSENSUS, TOWARDS THE MESOSCALE MODEL INTENSITY SOLUTIONS. DUE TO THE 1247 NM SPREAD IN MODEL GUIDANCE AT TAU 120, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN