Tropical Storm KHANUN Advisory Sun Oct 15

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KHANUN)
WARNING NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 24W (KHANUN), LOCATED APPROXIMATELY 346 NM
SOUTHEAST OF HONG KONG, HAS TRACKED NORTHWESTWARD AT 08 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
INITIALLY SHOWED THAT A RAGGED EYE-LIKE FEATURE DEVELOPED BUT HAS
FILLED TOWARD THE END OF THE LOOP. OVERALL, THE SYSTEM IS NOW MORE
CONSOLIDATED AS CONVECTIVE BANDS WRAPPING FROM THE SOUTH HAVE
DEEPENED AND BECOME MORE ORGANIZED. THE INITIAL POSITION IS BASED
ON THE RAGGED EYE FEATURE WITH GOOD CONFIDENCE. THE INITIAL
INTENSITY OF 60 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY
AND OBJECTIVE DVORAK ESTIMATES AND REFLECTS THE IMPROVED STATE OF
THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES TS 24W IS IN AN AREA OF
MODERATE (15-20 KNOT) EASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY
A STRONG WESTWARD DIVERGENT OUTFLOW AND A STORM MOTION THAT IS IN-
PHASE WITH THE VWS. ALONG-TRACK SEA SURFACE TEMPERATURES AT 29-30
CELSIUS ARE ALSO FAVORABLE. THE CYCLONE IS TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF AN EXTENSION OF THE SUBTROPICAL RIDGE
(STR) TO THE NORTHEAST.
3. FORECAST REASONING.
     A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
     B. TS 24W WILL CONTINUE TO TRACK NORTHWESTWARD OVER THE NEXT
12 HOURS. AFTERWARD, A SECONDARY EXTENSION OF THE STR BUILDING IN
OVER SOUTH CHINA WILL ASSUME AND STEER THE SYSTEM WESTWARD. AFTER
TAU 48, THE NEW STEERING RIDGE WILL BUILD AND DEFLECT THE CYCLONE
SOUTHWESTWARD. OVER THE NEXT 24 HOURS, THE AFOREMENTIONED FAVORABLE
CONDITIONS WILL PREVAIL AND INTENSIFY THE SYSTEM TO A PEAK OF 70
KNOTS. AFTERWARD, INCREASING VWS, ENTRAINMENT OF LOW LEVEL COOL DRY
AIR FROM THE NORTH, THEN INTERACTION WITH THE ISLAND OF HAINAN,
WILL GRADUALLY WEAKEN THE SYSTEM. BY TAU 72, TS 24W WILL BE REDUCED
TO 40 KNOTS AS IT DRIFTS SOUTHWESTWARD IN THE GULF OF TONKIN.
NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT AND THE JTWC TRACK
FORECAST IS LAID WITH HIGH CONFIDENCE JUST SOUTH OF THE MULTI-MODEL
CONSENSUS.
     C. BEYOND TAU 72, TS KHANUN WILL MAKE LANDFALL OVER SOUTHERN
VIETNAM THEN QUICKLY DISSIPATE DUE TO STRONG VWS AND INTERACTION
WITH RUGGED TERRAIN. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT THROUGH THE EXTENDED PORTION OF THE FORECAST, WITH SOME
INCREASED SPREAD BEYOND TAU 96 AS THE SYSTEM WEAKENS AND THE MODELS
LOSE THE VORTEX. OVERALL THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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