WDPN31 PGTW 201500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (KOMPASU) WARNING
NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 13W (KOMPASU), LOCATED APPROXIMATELY 209 NM EAST-
NORTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWESTWARD AT 25 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY (MSI) SHOWS TIGHTLY CURVED BANDING WRAPPING INTO A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) EMBEDDED WITHIN THE
NORTHERN EXTENT OF A VERY BROAD HIGH-LATITUDE MONSOON GYRE. THE
INITIAL POSITION IS BASED WITH HIGH CONFIDENCE ON A LOW REFLECTIVITY
CIRCULATION FEATURE IN THE 201139Z AMSU-B IMAGE. THE INITIAL
INTENSITY OF 35 KNOTS IS BASED ON OBJECTIVE DVORAK ESTIMATES AND ON A
201047Z ASCAT PASS. UPPER LEVEL ANALYSIS INDICATES A ROBUST POLEWARD
OUTFLOW OFFSET BY MODERATE (15-20 KNOT) VERTICAL WIND SHEAR.
ADDITIONALLY, SEA SURFACE TEMPERATURES (SSTS) ARE MARGINALLY
SUPPORTIVE AT 26 DEGREES CELSIUS. THE CYCLONE IS TRACKING
NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF A SUBTROPICAL STEERING
RIDGE (STR).
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS KOMPASU WILL BEGIN EXTRA-TROPICAL TRANSITION AS IT CONTINUES
TRACKING ALONG THE STR, AND WILL RECURVE  TO THE NORTHEAST AFTER TAU
12 IN RESPONSE TO AN APPROACHING MID-LATITUDE TROUGH. CONCURRENTLY,
SSTS WILL FALL BELOW 26 DEGREES. TS 13W WILL BECOME A 30-KNOT
COLD-CORE LOW BY TAU 36 AS THE SYSTEM IS FULLY EMBEDDED IN THE
BAROCLINIC ZONE. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST.//