Tropical Storm SONGDA Advisory wo, 12-10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 23W (SONGDA) WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 23W (SONGDA), LOCATED APPROXIMATELY 618 NM EAST-
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 19
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS THAT THE SYSTEM HAS STARTED TO SHOW THE EFFECTS
OF THE HIGH VERTICAL WIND SHEAR (VWS) ASSOCIATED WITH THE STRONG MID-
LATITUDE WESTERLIES. THE STRUCTURE HAS STARTED TO ELONGATE TO THE
NORTHEAST AND THE EYE IS CLOUD FILLED IN VISIBLE SATELLITE IMAGERY.
AN 112058Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTS A MORE RAGGED CORE
STRUCTURE; HOWEVER, A DEEP CONVECTIVE RING STILL SURROUNDS THE EYE
FEATURE. THE CURRENT POSITION IS BASED ON THE 22-NM EYE IN THE MSI
IMAGERY. THE INTENSITY HAS BEEN DECREASED TO 120 KNOTS BASED ON AN
ASSESSMENT OF DECREASING DVORAK INTENSITY ESTIMATES FROM ALL
AGENCIES. ENVIRONMENTAL CONDITIONS CONTINUE TO DETERIORATE DUE
PRIMARILY TO THE AFOREMENTIONED HIGH VWS. TY 23W IS TRACKING
NORTHEASTWARD ALONG THE NORTHERN PERIPHERY OF THE DEEP-LAYERED SUB-
TROPICAL RIDGE.
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY SONGDA WILL CONTINUE ACCELERATING NORTHEASTWARD AS IT
EMBEDS DEEPER WITHIN THE MID-LATITUDE WESTERLY FLOW. THE CYCLONE
STRUCTURE WILL CONTINUE TO ELONGATE AND WEAKEN AS IT ENCOUNTERS VWS
OVER 40 KNOTS AND COOLING SEA SURFACE TEMPERATURES. TY SONGDA WILL
BEGIN EXTRA-TROPICAL TRANSITION (ETT) OVER THE NEXT 12 HOURS AND
COMPLETE ETT BY THE END OF THE FORECAST PERIOD. DYNAMIC MODEL
GUIDANCE REMAINS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE TO THE
FORECAST TRACK.//
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