WDPN31 PGTW 271500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 21W (DUJUAN) WARNING NR 24//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 21W (DUJUAN), LOCATED APPROXIMATELY 276 NM EAST-
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED WEST-NORTHWESTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A LARGE TO 45-NM EYE AND
HIGHLY SYMMETRIC DEEP CONVECTIVE BANDING WRAPPING TIGHLY INTO THE
EYE. THE INITIAL POSITION IS BASED ON THE EYE FEATURE AND
EXTRAPOLATED FROM A WELL-DEFINED MICROWAVE LOW REFLECTIVITY
CIRCULATION CENTER IN THE 271115Z SSMIS PASS WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY OF 125 KNOTS IS BASED ON CONGRUENT DVORAK
ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES
THE SYSTEM REMAINS IN A LOW (05-10 KNOT) VERTICAL WIND SHEAR AREA
WITH EXCELLENT RADIAL OUTFLOW ENHANCED BY A MICROSCALE ANTICYCLONE
ALOFT. ADDITIONALLY, ALONG-TRACK SEA SURFACE TEMPERATURES REMAIN
CONDUCIVE AT 29 DEGREES CELSIUS. THE CYCLONE IS TRANSITIONING TO A
NEW STEERING SUBTROPICAL RIDGE (STR) CURRENTLY ANCHORED OVER
SOUTHEAST CHINA. 
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY DUJUAN WILL MAINTAIN A WEST-NORTHWESTWARD TRAJECTORY AS THE
NEW STEERING STR BUILDS THEN FLATTENS OUT TO THE NORTH. THE
AFOREMENTIONED ENVIRONMENTAL CONDITIONS WILL PERSIST, HOWEVER, THE
TYPHOON WILL NOW GRADUALLY WEAKEN AS IT BEGINS TO INTERACT WITH
TAIWAN, MAKING LANDFALL BY TAU 24. AFTERWARDS, THE RUGGED MOUNTAINOUS
TERRAIN OF NORTHERN TAIWAN WILL SIGNIFICANTLY ERODE THE SYSTEM BUT
WILL STILL EMERGE AT TYPHOON STRENGTH IN THE COOLER TAIWAN STRAIT. TY
21W WILL MAKE A FINAL LANDFALL IN CHINA SOUTH OF FUZHOU AT TAU 36,
THEN RAPIDLY DECAY MAINLY DUE TO FRICTIONAL EFFECTS. BY TAU 72, THE
SYSTEM WILL BE REDUCED TO BELOW WARNING CRITERIA AFTER IT DEFLECTS
NORTHEASTWARD IN RESPONSE TO A MID-LATITUDE TROUGH APPROACHING FROM
THE NORTHWEST. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT UP TO
LANDFALL INTO CHINA THEN SPREADS OUT SIGNIFICANTLY. IN VIEW OF THIS,
THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK ONLY UP TO THAT
POINT.//
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