Tropical Storm CHOI-WAN Advisory Wed Oct 07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 23W (CHOI-WAN) WARNING NR 19//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 23W (CHOI-WAN), LOCATED APPROXIMATELY 864 NM
SOUTHEAST OF MISAWA, JAPAN, HAS TRACKED NORTHWARD AT 19 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A GENERAL WEAKENING TREND CORRESPONDING TO INCREASING
SOUTHWESTERLY VERTICAL WIND SHEAR (VWS). THIS TREND IS EVIDENT IN A
062154Z SSMIS 91GHZ IMAGE, WHICH SHOWS DEEP CONVECTION WRAPPING
BROADLY INTO AN ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC). THE
CURRENT POSITION IS BASED ON THE SSMIS 37GHZ IMAGE WITH GOOD
CONFIDENCE. THE INITIAL INTENSITY HAS BEEN REDUCED TO 65 KNOTS BASED
ON DVORAK CURRENT INTENSITY ESTIMATES OF 65 KNOTS (T4.0). UPPER-
LEVEL ANALYSIS DEPICTS A VIGOROUS POLEWARD OUTFLOW CHANNEL
ASSOCIATED WITH A DEEP TROUGH ENTRENCHED SOUTH OF JAPAN. TY
23W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP,
POLEWARD-ORIENTED STR.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TY CHOI-WAN WILL CONTINUE TO ACCELERATE NORTHWARD THROUGH THE
FORECAST PERIOD. TY 23W APPEARS TO HAVE PEAKED BUT WILL WEAKEN
SLOWLY THROUGH TAU 12 AS VWS WILL BE OFFSET BY THE STRONG POLEWARD
OUTFLOW. TY 23W HAS COMMENCED EXTRA-TROPICAL TRANSITION (ETT) AS IT
BEGINS TO INTERACT WITH THE BAROCLINIC ZONE AND WILL COMPLETE ETT BY
TAU 36 AS IT GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED
WITHIN THE MIDLATITUDE WESTERLIES. THE SYSTEM IS EXPECTED TO
MAINTAIN STORM FORCE WINDS AND EXPANSIVE GALE-FORCE WINDS, WHICH
COULD ENCROACH ON THE COASTAL REGIONS OF NORTHERN JAPAN. DYNAMIC
MODEL GUIDANCE REMAINS IN VERY TIGHT AGREEMENT THROUGHOUT THE
FORECAST PERIOD LEADING TO HIGH CONFIDENCE IN THE JTWC TRACK
FORECAST.//
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