Tropical Storm TALIM Advisory Sun Sep 17

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (TALIM) WARNING NR
36//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 20W (TALIM), LOCATED APPROXIMATELY 115 NM EAST OF
IWAKUNI, JAPAN, HAS TRACKED NORTHEASTWARD AT 26 KNOTS OVER THE
PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT AGENCY
SATELLITE POSITION FIXES AND OBSERVATIONAL AND RADAR DATA FROM THE
JAPAN METEOROLOGICAL AGENCY. THE INTENSITY OF 55 KNOTS IS CONSISTENT
WITH SUBJECTIVE DVORAK INTENSITY ESTIMATES FROM RJTD AND SYNOPTIC
OBSERVATIONS FROM REPORTING STATIONS ACROSS JAPAN. TS 20W HAS
CONTINUED TO ACCELERATE NORTHEASTWARD OVER THE PAST SIX HOURS IN THE
GRADIENT BETWEEN A SUBTROPICAL STEERING RIDGE TO THE SOUTHEAST AND A
MID-LATITUDE TROUGH TO THE NORTHWEST. RECENT CHANGES IN KEY STORM
CHARACTERISTICS, SUCH AS THE NOTED ACCELERATION IN FORWARD MOTION
AND ASYMMETRIC CONVECTIVE DEVELOPMENT, INDICATE THAT TS 20W HAS
BEGUN TO MERGE WITH THE MID-LATITUDE TROUGH, COMMENCING THE INITIAL
STAGE OF EXTRATROPICAL TRANSITION.
3. FORECAST REASONING.
   A. THE FORECAST TRACK HAS AGAIN SHIFTED SLIGHTLY TO THE RIGHT
BASED ON RECENT STORM MOTION RELATIVE TO THE PREVIOUS FORECAST.
HOWEVER, THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 20W WILL COMPLETE EXTRATROPICAL TRANSITION WITHIN THE NEXT
12 HOURS AS IT TRACKS RAPIDLY NORTHEASTWARD. FAVORABLE BAROCLINIC
INTERACTION BETWEEN TS 20W AND THE MID-LATITUDE TROUGH DURING
EXTRATROPICAL TRANSITION WILL ALLOW THE SYSTEM TO MAINTAIN AN
EXPANSIVE AREA OF LOW-LEVEL GALE-FORCE AND STRONGER WINDS. GIVEN THE
SIZE OF THIS WIND FIELD, POTENTIALLY SIGNIFICANT WEATHER IMPACTS
SHOULD BE ANTICIPATED THROUGHOUT MAINLAND JAPAN - PARTICULARLY IN
COASTAL AREAS - FOR THE NEXT 24 HOURS. BASED ON CONTINUED TIGHT
AGREEMENT AMONG FORECAST MODELS, THERE IS HIGH CONFIDENCE IN THE
CURRENT JTWC OFFICIAL TRACK FORECAST.//
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