Tropical Storm DUJUAN Advisory Sat Sep 26

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 21W (DUJUAN) WARNING NR 20//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 21W (DUJUAN), LOCATED APPROXIMATELY 282 NM SOUTH-
SOUTHEAST OF KADENA AB, JAPAN HAS TRACKED NORTHWESTWARD AT
09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY SHOWS AN IMPROVED CONVECTIVE CORE STRUCTURE WITH
COOLER CLOUD TOPS SURROUNDING A LARGE 38NM EYE WHICH SUPPORTS THE
INITIAL POSITION WITH HIGH CONFIDENCE. THE WATER VAPOR LOOP SHOWS A
MORE SYMMETRIC CORE STRUCTURE WITH DECREASED DRY AIR IMPACTING THE
TYPHOON. A 261230Z AMSU-B MICROWAVE IMAGE SHOWS A CLOSED OFF
MICROWAVE EYE FEATURE SURROUNDED BY AN INTENSE CONVECTIVE CORE. THE
CURRENT INTENSITY HAS BEEN INCREASED TO 95 KNOTS BASED ON AN
ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL AGENCIES AND IS
SUPPORTED BY A RECENT SATCON INTENSITY ESTIMATE OF 97 KNOTS.
ENVIRONMENTAL ANALYSIS INDICATES AN IMPROVED ENVIRONMENT WITH NEAR
RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR (VWS). TY DUJUAN IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP LAYERED SUB-
TROPICAL RIDGE.
3. FORECAST REASONING.
   A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY DUJUAN WILL MAINTAIN A WEST-NORTHWESTWARD TRAJECTORY
THROUGHOUT THE FORECAST PERIOD AS THE STEERING STR CONTINUES TO
BUILD OVER THE SYSTEM. CURRENT ENVIRONMENTAL CONDITIONS WILL SUPPORT
A SLIGHT INTENSIFICATION OVER THE NEXT 24 HOURS. BEYOND TAU 24, TY
21W WILL BEGIN TO WEAKEN DUE TO LOWER OHC VALUES, AN INCREASE IN
VWS AND LAND INTERACTION WITH THE MOUNTAINOUS TERRAIN OF TAIWAN. DUE
TO THE HIGH LIKELIHOOD OF A LEEWARD JUMP SCENARIO AS THE TYPHOON
PASSES THROUGH TAIWAN, THERE IS LIMITED CONFIDENCE IN THE TAU 72
POSITION.
   C. IN THE EXTENDED FORECAST, TY 21W WILL MAKE A SECOND LANDFALL
ALONG THE COAST OF CHINA AND WILL RAPIDLY DISSIPATE BY THE END OF
THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGHOUT THE FORECAST PERIOD WITH A SPREAD OF 130NM AT TAU 48 JUST
PRIOR TO LANDFALL OVER TAIWAN. THIS TIGHT MODEL AGREEMENT LEADS TO
HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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