Tropical Storm FENGSHEN Advisory 11月16日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (FENGSHEN) WARNING NR 018//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 26W (FENGSHEN), LOCATED APPROXIMATELY 153 NM SOUTH-
SOUTHEAST OF IWO TO, JAPAN, HAS TRACKED NORTHWARD AT 14 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
(EIR) SHOWS THE SYSTEM HAS MAINTAINED OVERALL EIR SIGNATURE AND A
PINHOLE 10NM EYE SURROUNDED BY DEEP COMPACT CENTRAL CONVECTION. THE
INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON THE EYE
FEATURE, ADJUSTED FOR A SLIGHT TILT. THE INITIAL INTENSITY OF 110KTS
IS AVERAGED FROM AGENCY DVORAK ESTIMATES OF T5.5/102KTS TO
T6.0/115KTS AND REFLECTS THE SUSTAINED EIR STRUCTURE. TY 26W HAS
DRIFTED INTO AN AREA OF LOW TO MODERATE (10-15KT) VERTICAL WIND
SHEAR (VWS), OFFSET BY WARM (28-29C) SSTS AND EXCELLENT POLEWARD
OUTFLOW. THE CYCLONE HAS CRESTED THE WESTERN EDGE OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A.  THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 26W IS FORECAST TO TRACK NORTHEASTWARD THEN EASTWARD ON THE
POLEWARD SIDE OF THE STR. AFTER TAU 36, AS THE SYSTEM ERODES DUE TO
INCREASING VWS AND COOLING SSTS, A SECONDARY, MID-LAYERED STR TO THE
NORTH WILL ASSUME STEERING AND DRIVE THE SYSTEM WEST-SOUTHWESTWARD.
BY TAU 72, TY 26W WILL BE REDUCED TO 55KTS.
   C. AFTER TAU 72, THE SYSTEM, STILL UNDER THE SECONDARY STR, WILL
TURN NORTHWESTWARD. THE NEGATIVE COMBINED EFFECTS OF HIGH VWS AND
COOL SSTS WILL RESULT IN DISSIPATION BY TAU 96. THE MAJORITY OF THE
NUMERICAL MODELS ARE IN BROAD 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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