Tropical Storm DOKSURI Advisory gio, 14.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (DOKSURI)
WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 21W (DOKSURI), LOCATED APPROXIMATELY 225 NM EAST OF DA
NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS.  ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS
STRONG CONVECTION SOUTH OF THE LOW LEVEL CIRCULATION CENTER (LLCC)
WITH CONVECTION STARTING TO DEVELOP AND WRAP INTO A NASCENT EYE
FEATURE. THE LATEST MICROWAVE IMAGE AVAILABLE WAS FROM 131904Z,
WHICH SHOWED A DEVELOPING MICROWAVE EYE IN THE 89 GHZ BAND. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON HIGH
RESOLUTION VISIBLE IMAGERY, AND NEAR THE MULTI-AGENCY FIX LOCATIONS.
THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON SUBJECTIVE DVORAK
CURRENT INTENSITY ESTIMATES OF T4.0 (65 KNOTS) FROM BOTH PGTW AND
KNES. ANALYSIS SHOWS THE SYSTEM IS IN A FAVORABLE ENVIRONMENT, WITH
LOW VERTICAL WIND SHEAR (VWS) (10-15 KNOTS), ROBUST EQUATORWARD
OUTFLOW ALOFT AND SEA SURFACE TEMPERATURES OF 30-31 CELSIUS. TY 21W
IS MOVING WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF A DEEP-
LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH AS WELL A STR EXTENSION
WHICH IS BUILDING WESTWARD OVER THE PHILIPPINES.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY DOKSURI WILL CONTINUE TO TRACK GENERALLY WESTWARD AND WILL
PASS SOUTH OF HAINAN ISLAND BEFORE EVENTUALLY MAKING LANDFALL IN
NORTHERN VIETNAM.  THE STR LOCATED TO THE NORTH WILL CONTINUE TO
BUILD, KEEPING THE FORECAST TRACK WESTERLY.  ENVIRONMENTAL
CONDITIONS INCLUDING STRONG EQUATORWARD OUTFLOW AND DIVERGENCE
ALOFT, HIGH SEA SURFACE TEMPERATURES AND LOW VWS, WILL ALL REMAIN
FAVORABLE FOR THE INTENSIFICATION OF TY 21W. ADDITIONALLY, BY TAU 12
TY 21W WILL BE LOCATED OVER SEA SURFACE TEMPERATURES IN EXCESS OF 31
CELSIUS, PROVIDING A SOURCE OF ADDITIONAL INTENSIFICATION. TY 20W IS
EXPECTED TO REACH PEAK INTENSITY OF 90 KNOTS BEFORE MAKING LANDFALL
SHORTLY AFTER TAU 48, THEREAFTER RAPIDLY DECREASE IN INTENSITY AND
FORWARD SPEED AND DISSIPATE BY TAU 72.  MODEL TRACK GUIDANCE REMAINS
IN VERY TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC TRACK
FORECAST.//
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