Tropical Storm KHANUN Advisory Mon Oct 16

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KHANUN) WARNING NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (KHANUN), LOCATED APPROXIMATELY 108 NM
SOUTH-SOUTHWEST OF HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 17
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS A MORE COMPACT CENTRAL DENSE OVERCAST FEATURE
CONTINUED TO CONSOLIDATE AND DEEPEN AROUND A SUNKEN BUT VISIBLE
CLOUD-FILLED EYE. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EYE FEATURE. THE INITIAL INTENSITY OF 90
KNOTS IS BASED ON AN OVERALL ASSESSMENT OF CLOSELY CLUSTERED MULTI-
AGENCY AND OBJECTIVE DVORAK FIXES AND REFLECTS THE IMPROVED STATE OF
THE CYCLONE. ENVIRONMENTAL ANALYSIS INDICATES THAT TY 24W IS IN A
FAVORABLE ENVIRONMENT WITH MODERATE (15-20 KNOT) EASTERLY VERTICAL
WIND SHEAR (VWS) THAT IS, FOR NOW, MOSTLY OFFSET BY THE ACCELERATED
STORM MOTION THAT IS IN-PHASE WITH THE VWS DIRECTION, RESULTING IN A
LOWER RELATIVE SHEAR VALUE. OUTFLOW IS MARGINAL WITH JUST AN
EQUATORWARD OUTFLOW CHANNEL. SEA SURFACE TEMPERATURES AT 30 DEG
CELSIUS ALSO REMAIN FAVORABLE. TY 24W IS TRACKING ALONG THE
SOUTHWESTERN PERIPEHRY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST.
3. FORECAST REASONING.
     A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
     B. TY KHANUN WILL TRACK MORE WESTWARD THEN SOUTHWESTWARD AS THE
STR BUILDS AND REORIENTS, CROSSING THE CHINESE LEIZHOU PENINSULA INTO
THE GULF OF TONKIN BEFORE TURNING TOWARD CENTRAL VIETNAM. THE SYSTEM
MAY HAVE PEAKED IN INTENSITY AS IT WILL NOW BEGIN TO INTERACT WITH
THE CHINESE LANDMASS. ADDITIONALLY, AS THE STORM MOTION BECOMES MORE
SOUTHWESTWARD, VWS WILL INCREASE RESULTING IN A MORE RAPID DECAY. BY
TAU 48, TY 24W WILL BE REDUCED TO A 35-KNOT TROPICAL STORM BEFORE
MAKING LANDFALL JUST NORTH OF HUE, VIETNAM, THEN DISSIPATE RAPIDLY
OVER ROUGH TERRAIN BY TAU 72. MODEL GUIDANCE IS IN GOOD AGREEMENT UP
TO TAU 24 THEN SPREADS OUT SIGNIFICANTLY. THERE IS HIGH CONFIDENCE
IN THE FIRST DAY OF THE JTWC TRACK FORECAST THEN LOW CONFIDENCE
AFTERWARD.//
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