Tropical Storm FENGSHEN Advisory dom, 17-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (FENGSHEN) WARNING NR 020//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 26W (FENGSHEN), LOCATED APPROXIMATELY 185 NM EAST OF
IWO TO, JAPAN, HAS TRACKED NORTHEASTWARD AT 17 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A
SYMMETRIC EYEWALL SURROUNDING A 13-NM RAGGED EYE, WHICH SUPPORTS THE
INITIAL POSITION WITH GOOD CONFIDENCE. A 160334Z AMSR2 89GHZ IMAGE,
HOWEVER, REVEALS AN ASYMMETRIC CONVECTIVE STRUCTURE WITH DEEP
CONVECTIVE BANDING WRAPPING INTO A MICROWAVE EYE FEATURE. UPPER-
LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH
MODERATE VERTICAL WIND SHEAR (VWS) OFFSET BY ROBUST POLEWARD
OUTFLOW. THE INITIAL INTENSITY IS ASSESSED AT 110 KNOTS BASED ON
DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM 5.5 TO 6.0 (102 TO
115 KNOTS). TY 26W HAS ROUNDED THE SUBTROPICAL RIDGE (STR) AXIS AND
IS ACCELERATING WITHIN THE MIDLATITUDE WESTERLIES.
3. FORECAST REASONING.
   A.  THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 26W WILL TRACK EAST-NORTHEASTWARD TO EASTWARD WHILE
WEAKENING RAPIDLY UNDER INCREASING, STRONG (40-50 KNOTS) VWS. AFTER
TAU 36, TY 26W WILL WEAKEN SIGNIFICANTLY, GRADUALLY SLOW AND TURN
SOUTHWARD THEN WESTWARD AS A STRONG LOW-LEVEL HIGH BUILDS TO THE
NORTH. THE SYSTEM IS EXPECTED TO DISSIPATE BY TAU 72 WITH THE
REMNANTS TRACKING POLEWARD. THE MAJORITY OF THE NUMERICAL MODELS ARE
IN GENERAL AGREEMENT WITH THIS LOOPING TRACK BUT WITH SIGNIFICANT
DIFFERENCES IN THE TRACK SPEED AND THE TIMING OF THE TURNS. IN VIEW
OF THIS COMPLEX STEERING AND THE LARGE VARIANCE IN THE NUMERICAL
MODEL SOLUTIONS, THERE IS LOW CONFIDENCE IN THE JTWC TRACK
FORECAST.//
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