Tropical Storm YUTU Advisory Fri Oct 26

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.//
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