WDPN31 PGTW 292100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (SINLAKU) WARNING 
NR 15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 21W (SINLAKU), LOCATED APPROXIMATELY 138 NM 
SOUTH-SOUTHEAST OF DA NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD 
AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE 
IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER 
(LLCC) WITH DEEP CONVECTIVE BANDING DISPLACED OVER THE WESTERN SEMI- 
CIRCLE OF THE LLCC. A 291438Z METOP-A 91 GHZ IMAGE DEPICTS DEEP 
CONVECTIVE BANDING OVER THE WESTERN QUADRANT WITH TIGHTLY-WRAPPED 
SHALLOW BANDING ELSEWHERE, WRAPPING INTO A WELL-DEFINED CENTER. 
OVERALL, THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION OF THE 
SYSTEM OVER CENTRAL VIETNAM. THE INITIAL INTENSITY OF 45 KNOTS IS 
BASED ON DVORAK INTENSITY ESTIMATES RANGING FROM ALL AGENCIES WITH 
THE SYSTEM STARTING TO DISSIPATE DUE TO LAND INTERACTION. UPPER-
LEVEL ANALYSIS INDICATES MODERATE (15 KNOTS) EASTERLY VERTICAL WIND 
SHEAR OFFSET BY DIFFLUENT FLOW. TS SINLAKU IS CURRENTLY TRACKING 
ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC 
REASONING MESSAGE.
   B. TS SINLAKU IS FORECAST TO CONTINUE TO TRACK WESTWARD THROUGH 
THE FORECAST PERIOD OVER LAND, DISSIPATING RAPIDLY. THE DYNAMIC 
MODELS ARE IN TIGHT AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE 
IN THE JTWC FORECAST.//
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