Tropical Storm DOKSURI Advisory Thu Sep 14

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (DOKSURI)
WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 21W (DOKSURI), LOCATED APPROXIMATELY 298 NM WEST OF
MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS
FRAGMENTED BUT DEEP CONVECTIVE BANDS FEEDING INTO A WELL-DEFINED LOW
LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE BANDING LLC. THE INITIAL INTENSITY OF 45
KNOTS IS BASED ON DVORAK ESTIMATE OF T3.0 FROM RJTD AND PGTW.
ENVIRONMENTAL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF LOW
(10-15 KNOT) VERTICAL WIND SHEAR (VWS), GOOD EQUATORWARD OUTFLOW, AND
IS DRIFTING OVER VERY WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES
(SSTS). TS 21W IS TRACKING UNDER THE INFLUENCE OF AN EXTENSION OF THE
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 21W WILL CONTINUE TO TRACK WEST-NORTHWESTWARD IN THE SOUTH
CHINA SEA UNDER THE INFLUENCE OF THE STR THROUGHOUT THE FORECAST. BY
TAU 48, THE CYCLONE WILL REACH THE GULF OF TONKIN AND POISED TO MAKE
LANDFALL INTO NORTHERN VIETNAM. THE FAVORABLE ENVIRONMENT WILL ALLOW
FOR STEADY INTENSIFICATION, PEAKING AT 80 KNOTS BY TAU 48. AFTER
LANDFALL, THE SYSTEM WILL RAPIDLY WEAKEN TO 55 KNOTS BY TAU 72.
DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE
IN THIS PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, TS DOKSURI WILL CONTINUE TO RAPIDLY ERODE DUE TO
FRICTIONAL EFFECTS OF THE RUGGED TERRAIN AND DISSIPATE OVER THE
MOUNTAINS OF THAILAND BY TAU 96. DYNAMIC MODEL GUIDANCE IS ALSO IN
GOOD AGREEMENT, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC
TRACK FORECAST.//
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