Tropical Storm EWINIAR Advisory mer, 26.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (EWINIAR)
WARNING NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 19W (EWINIAR), LOCATED APPROXIMATELY 40 NM
NORTH OF IWO-TO, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 08 KNOTS
OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON A PGTW
SATELLITE FIX AND A 252150Z TRMM PASS. THE CURRENT INTENSITY OF 50
KNOTS IS CONSISTENT WITH RECENT DVORAK CURRENT INTENSITY ESTIMATES
AND LOW-LEVEL STRUCTURE EVIDENT IN THE TRMM PASS. TS 19W IS MOVING
NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL STEERING
RIDGE TO THE EAST. DEEP CONVECTION REMAINS CONFINED TO THE EASTERN
PERIPHERY OF THE LOW-LEVEL CIRCULATION CENTER (LLCC) DUE TO
PERSISTENT VERTICAL WIND SHEAR INDUCED BY EASTERLY FLOW AHEAD OF AN
UPPER-LEVEL TROUGH TO THE WEST.
3. FORECAST REASONING.
   A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 19W IS FORECAST TO TURN FROM A NORTHEASTWARD TRACK TO A
NORTHWARD TRACK IN THE UPCOMING 12 HOURS AS THE STEERING RIDGE
WEAKENS WITH THE APPROACH OF THE AFOREMENTIONED TROUGH CURRENTLY
ANALYZED TO THE WEST OF THE CYCLONE. BETWEEN TAU 24 AND TAU 48, TS
19W IS EXPECTED TO SLOW SIGNIFICANTLY AS IT INTERACTS WITH AN UPPER-
LEVEL LOW DEVELOPING AT THE BASE OF THE APPROACHING TROUGH.
THEREAFTER, TS 19W WILL ACCELERATE NORTHEASTWARD AHEAD OF A SECOND
MIDLATITUDE TROUGH. THE SYSTEM IS EXPECTED TO INTENSIFY A BIT OVER
THE NEXT 24 HOURS WITH STRONG DIFFLUENCE ALOFT AND PASSAGE OVER WARM
WATER. AS THE CYCLONE ENCOUNTERS A BAROCLINIC ZONE AFTER TAU 48 IT
WILL WEAKEN SLOWLY AND BEGIN EXTRATROPICAL TRANSITION.
   C. IN THE EXTENDED PERIOD, TS 19W WILL ACCELERATE NORTHEASTWARD
AHEAD OF A MIDLATITUDE TROUGH AND COMPLETE EXTRATROPICAL TRANSITION
BY TAU 96. INCREASING VERTICAL WIND SHEAR AND PASSAGE OVER COOLER
WATER WILL ALLOW SLOW WEAKENING TO CONTINUE AS THE SYSTEM COMPLETES
THE TRANSITION INTO A COLD CORE LOW. THE NUMERICAL MODEL GUIDANCE IS
IN GOOD OVERALL AGREEMENT AND THE CURRENT TRACK FORECAST LIES
SLIGHTLY AHEAD OF THE CONSENSUS IN THE EXTENDED PERIOD. THERE IS
HIGH CONFIDENCE IN ALL TAUS OF THE CURRENT FORECAST TRACK.//
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