Tropical Storm VONGFONG Advisory lun, 13.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (VONGFONG) WARNING
NR 42//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 19W (VONGFONG), LOCATED APPROXIMATELY 102 NM
SOUTH-SOUTHEAST OF SASEBO, JAPAN, HAS TRACKED EAST-NORTHEASTWARD
AT 19 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICTS A BROAD, NOW FULLY-EXPOSED, LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH LIMITED DEEP CONVECTION SHEARED OVER
THE NORTHERN SEMI-CIRCLE OF THE LLCC. A 122322Z SSMIS MICROWAVE
IMAGE ADDITIONALLY SHOWS THE OVERALL STRUCTURE IS STARTING TO
ELONGATE AS IT BEGINS TO ENCOUNTER LAND. DUE TO THE BROADENING
NATURE OF THE LLCC THERE IS DECREASING CONFIDENCE IN THE INITIAL
POSITION AND MOTION. THE INITIAL INTENSITY ASSESSMENT HAS BEEN
DECREASED TO 5O KNOTS AS THE OBSERVATIONS ACROSS KYUSHU SUGGEST THE
SYSTEM HAS WEAKENED. DVORAK INTENSITY ESTIMATES CONTINUE TO FALL AS
THE CONVECTIVE ORGANIZATION WEAKENS AND MAY BE UNREPRESENTATIVE OF
THE CURRENT INTENSITY. UPPER-LEVEL ANALYSIS, ALONG WITH ANIMATED
WATER VAPOR IMAGERY, REVEALS A HOSTILE ENVIRONMENT AS STRONG (30 TO
40 KNOTS) SOUTHWESTERLY VERTICAL WIND SHEAR IS OFFSETTING ENHANCED
POLEWARD OUTFLOW INTO THE MIDLATITUDE WESTERLIES. TS 19W IS
ACCELERATING TO THE NORTHEAST AS IT TRACKS ALONG THE NORTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 19W IS FORECAST TO CONTINUE TO ACCELERATE TO THE NORTHEAST
THROUGH THE REMAINDER OF THE FORECAST PERIOD AS AN APPROACHING
MIDLATITUDE TROUGH DIGS IN FROM THE KOREAN PENINSULA AND PRESSES ON
THE STR. AS THE SYSTEM GAINS LATITUDE AND DRAGS ACROSS JAPAN, EXTRA-
TROPICAL TRANSITION (ETT) WILL BEGIN DUE TO THE SYSTEM BECOMING
EMBEDDED IN THE MID-LATITUDE WESTERLIES. ETT, ALONG WITH INCREASED
LAND INTERACTION, WILL INDUCE A WEAKENING TREND AS THE SYSTEM
BROADENS AND GAINS BAROCLINIC ENERGY WITH THE STRONGEST WINDS
MIGRATING INTO THE DEVELOPING FRONTAL FEATURES. TS 19W IS EXPECTED
TO COMPLETE ETT BY TAU 24 AS IT APPROACHES THE KANTO PLAIN AS A GALE
FORCE, COLD-CORE, LOW. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT
WITH THE FORECAST SCENARIO AND TRACK; THEREFORE, THERE IS HIGH
CONFIDENCE IN THE FORECAST.//
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