Tropical Storm YUTU Advisory Sat Oct 27

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (YUTU) WARNING NR
20//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON 31W (YUTU), LOCATED APPROXIMATELY 391 NM WEST-
NORTHWEST OF NAVSTA GUAM, HAS TRACKED WESTWARD AT 13 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS STY
31W HAS MAINTAINED A STRONG, SYMMETRIC CONVECTIVE EYEWALL AND WELL-
DEFINED EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE 22NM-WIDE EYE IN ENHANCED INFRARED SATELLITE IMAGERY.
HOWEVER, RECENT ANIMATED SATELLITE IMAGERY CONTINUES TO INDICATE
TROCHOIDAL TRACK MOTION. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE
ENVIRONMENT WITH LOW (10 TO 15 KNOTS) EASTERLY VERTICAL WIND SHEAR
AND ROBUST OUTFLOW WITH THE EXCEPTION OF THE EASTERN QUADRANT, WHERE
AN UPPER LEVEL ANTICYCLONE TO THE EAST IS IMPINGING ON UPPER LEVEL
OUTFLOW. THE INITIAL INTENSITY IS HELD AT SUPER TYPHOON STRENGTH
(130 KTS) BASED ON THE PGTW AND KNES DVORAK CURRENT INTENSITY
ESTIMATES OF T6.5 (127 KTS), UNDER THE 260332Z SATCON ESTIMATE OF
140 KTS, BUT CONSISTENT WITH THE AUTOMATED DVORAK TECHNIQUE ESTIMATE
OF 132 KTS. STY 31W IS TRACKING WEST-NORTHWESTWARD ALONG THE
SOUTHWEST PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) POSITIONED TO
THE NORTHEAST. THERE IS A BREAK IN THE STR TO THE NORTHWEST OF THE
SYSTEM ASSOCIATED WITH A WEAK MIDLATITUDE SHORTWAVE TROUGH MOVING
INTO THE YELLOW SEA.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE. WIND RADII WERE ADJUSTED
BASED ON A 260034Z ASCAT IMAGE.
   B. STY 31W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD
TOWARD THE BREAK IN THE STR THROUGH TAU 36, HOWEVER, THE SYSTEM
SHOULD GRADUALLY TURN MORE WESTWARD AFTER TAU 36 AS THE
AFOREMENTIONED SHORTWAVE TROUGH PROPAGATES EASTWARD AND A BROAD
MIDLATITUDE RIDGE TO THE NORTH ALLOWS THE STR TO RE-BUILD. EXCLUDING
THE PRIMARY OUTLIERS, COAMPS-TC (CTCX) AND NAVGEM, DYNAMIC MODEL
GUIDANCE IS IN BETTER AGREEMENT THROUGH TAU 72 WITH A 140NM SPREAD
IN SOLUTIONS AT TAU 72. STY 31W IS EXPECTED TO MAINTAIN NEAR-STY
STRENGTH THROUGH TAU 12 AS THE EYEWALL RE-STRENGTHENS AND THE EYE
CONTRACTS. HOWEVER, AFTER TAU 12, THE SYSTEM SHOULD GRADUALLY WEAKEN
AS VERTICAL WIND SHEAR INCREASES TO MODERATE LEVELS.
   C. BEYOND TAU 72, THERE IS INCREASING UNCERTAINTY IN THE FORECAST
TRACK WITH TWO DISTINCT CLUSTERS OF MODEL GUIDANCE. ECMWF, EEMN,
UKMET, JGSM, AFUM, GFS, AEMN AND HWRF INDICATE A WEST-SOUTHWESTWARD
(OVER LUZON) TO WEST-NORTHWESTWARD (TOWARD THE LUZON STRAIT) TRACK.
NAVGEM, COAMPS-NAVGEM, AND COAMPS-GFS CONTINUE TO INDICATE AN
UNLIKELY RECURVE SCENARIO. THOUGH THE MIDLATITUDE TROUGH WILL CREATE
A BREAK IN THE STR, THE TROUGH WILL BE ASSOCIATED WITH A COLD
NORTHEASTERLY SURFACE SURGE THAT WILL PREVENT THE SYSTEM FROM
RECURVING SIGNIFICANTLY NORTH. THE JTWC FORECAST TRACK FAVORS A MORE
WESTWARD TRACK WITH A DECREASE IN TRACK SPEEDS ASSOCIATED WITH A
BREAK IN THE STR AND THE SURFACE COLD SURGE. STY 31W WILL CONTINUE
TO GRADUALLY WEAKEN UNDER INCREASING VERTICAL WIND SHEAR AND THE
COLD, DRY AIR ASSOCIATED WITH THE NORTHEASTERLY COLD SURGE, ALTHOUGH
SSTS REMAIN FAVORABLE INTO THE LUZON STRAIT, BETWEEN 26-27 DEGREES
CELSIUS. BASED ON THE BIFURCATION IN THE DYNAMIC MODELS AND LARGE
OVERALL SPREAD, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.//
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