Tropical Storm ATSANI Advisory Tu, 25-08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (ATSANI) WARNING NR 41//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 17W (ATSANI), LOCATED APPROXIMATELY 500 NM
EAST-SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 11
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULSPECTRAL SATELLITE IMAGERY
(MSI) SHOWS SPIRAL BANDING HAVE MAINTAINED THEIR DEGREE OF WRAP
AROUND A RAGGED, ALBEIT WELL-DEFINED LOW LEVEL CIRCULATION. THE
INITIAL POSITION IS BASED ON THE ANIMATED MSI WITH GOOD CONFIDENCE.
THE INITIAL INTENSITY OF 65 KNOTS IS CONSISTENT WITH DVORAK ESTIMATES
FROM ALL REPORTING AGENCIES. UPPER LEVEL ANALYSIS INDICATES LOW TO
MODERATE (10-15 KNOT) VWS THAT IS MOSTLY OFFSET BY GOOD RADIAL
OUTFLOW. THE NORTHERN EXTENT OF THIS EXPANSIVE SYSTEM HOWEVER IS
UNDER CONSIDERABLY HIGHER VWS AND IS INTERACTING WITH THE
MID-LATITUDE BAROCLINIC ZONE. TY 17W IS TRACKING ALONG THE
NORTHWESTERN PERIPHERY OF THE DEEP-
LAYERED SUB-TROPICAL RIDGE (STR) LOCATED TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 17W WILL CONTINUE NORTHEASTWARD IN THE MID-LATITUDE
WESTERLY FLOW. SEA SURFACE TEMPERATURES WILL DROP BELOW 26 CELSIUS
OVER THE NEXT 12-24 HOURS AND THE SYSTEM WILL BEGIN EXTRA-TROPICAL
TRANSITION (ETT). THE ETT WILL BE COMPLETE BY TAU 48. GOOD OUTFLOW
AND LOW VWS WILL SOMEWHAT OFFSET COLDER SSTS, RESULTING IN A GRADUAL
WEAKENING TREND. TY 17W IS THEREFORE EXPECTED TO BECOME A STRONG
GALE-FORCE COLD CORE LOW BY THE END OF THE FORECAST PERIOD.//
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