Tropical Storm LAN Advisory Sa, 21.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 25W (LAN) WARNING NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 25W (LAN), LOCATED APPROXIMATELY 358 NM SOUTH-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTHEASTWARD AT 08 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
A SYMMETRIC EYEWALL SURROUNDING A 50NM ROUND EYE. STY 25W HAS
RAPIDLY INTENSIFIED (RI) OVER THE PAST 24 HOURS FROM 85 KNOTS TO
135 KNOTS (50 KNOTS). UPPER-LEVEL ANALYSIS INDICATES EXCELLENT
OUTFLOW, PARTICULARLY POLEWARD, WHICH IS TAPPING INTO THE
MIDLATITUDE WESTERLIES OVER JAPAN. A 202147Z WINDSAT 37GHZ IMAGE
SHOWS SPIRAL BANDING WRAPPING INTO THE SYSTEM WITH A WELL-DEFINED
MICROWAVE EYE FEATURE. THE INITIAL INTENSITY IS ASSESSED AT 135
KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM T6.5
(127 KNOTS) TO T7.0 (140 KNOTS). STY 25W IS TRACKING POLEWARD ALONG
THE WESTERN PERIPHERY OF THE DEEP LAYERED SUBTROPICAL RIDGE.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. ANIMATED SATELLITE IMAGERY INDICATES SOME EYE WOBBLE, HOWEVER,
STY 25W IS TRACKING GENERALLY POLEWARD TOWARD CENTRAL JAPAN. STY LAN
SHOULD REMAIN AT STY STRENGTH THROUGH THE NEXT 12 HOURS THEN WEAKEN
AS IT APPROACHES JAPAN AND BEGINS TO INTERACT WITH THE BAROCLINIC
ZONE BY TAU 24. AFTER TAU 24, STY 25W WILL ENCOUNTER STRONG VERTICAL
WIND SHEAR, BEGIN TO INTERACT WITH LAND AND WILL WEAKEN
SIGNIFICANTLY. THE SYSTEM WILL COMPLETE EXTRA-TROPICAL TRANSITION BY
TAU 48 AS IT GAINS FRONTAL CHARACTERISTICS AND BEGINS TO ACCELERATE
NORTHEASTWARD. STY 25W IS FORECAST TO MAINTAIN EXTENSIVE GALE-FORCE
WINDS DUE TO THE VERY LARGE SIZE OF THE SYSTEM, AND PROXIMITY OF
COLD-SURGE WINDS AND GRADIENT WINDS ASSOCIATED WITH THE FRONTAL ZONE
CURRENTLY SITUATED OVER JAPAN. DYNAMIC MODEL GUIDANCE REMAINS IN
TIGHT AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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