Tropical Storm KHANUN Advisory Вс, 15.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KHANUN)
WARNING NR 11//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (KHANUN), LOCATED APPROXIMATELY 217 NM
SOUTHEAST OF HONG KONG, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
SHOWS THE OVERALL STRUCTURE OF THE SYSTEM HAS RAPIDLY IMPROVED OVER
THE PAST SIX HOURS, WITH A BROAD AND RAGGED EYE FEATURE DEVELOPING
IN THE RECENT IMAGERY. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON A MICROWAVE EYE FEATURE VISIBLE IN 141726Z GPM
37GHZ AND 89GHZ MICROWAVE IMAGERY. THE INITIAL INTENSITY IS SET AT
70 KNOTS BASED ON AN OVERALL ASSESSMENT OF MULTI-AGENCY SUBJECTIVE
DVORAK INTENSITY ESTIMATES OF T4.0 (65 KNOTS), HEDGED SLIGHTLY
HIGHER IN LIGHT OF THE OVERALL APPEARANCE IN MICROWAVE AND INFRARED
IMAGERY AND AUTOMATED DVORAK TECHNIQUE (ADT) ESTIMATES OF T4.3 (72
KNOTS). ENVIRONMENTAL ANALYSIS INDICATES THAT AS TY 24W HAS MOVED
MORE NORTHERLY THAN EXPECTED, IT HAS MOVED INTO A MORE FAVORABLE
ENVIRONMENT, WITH MODERATE (15-20 KNOTS) EASTERLY VERTICAL WIND
SHEAR (VWS) OFFSET BY A STRONG WESTWARD DIVERGENT OUTFLOW AND ITS
STORM MOTION THAT IS IN-PHASE WITH THE VWS VECTOR. SEA SURFACE
TEMPERATURES ARE SLIGHTLY LOWER THAN PREVIOUS FORECASTS, BUT REMAIN
SUPPORTIVE AT 28-29 DEG CELSIUS. THE SYSTEM IS TRACKING ALONG THE
SOUTHWESTERN BOUNDARY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED NEAR TAIWAN.
3. FORECAST REASONING.
     A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
     B. TY 24W WILL CONTINUE TO TRACK NORTHWESTWARD OVER THE NEXT
12 HOURS. THEREAFTER, AN EXTENSION OF A DEEP-LAYER RIDGE OVER
SOUTHERN CHINA WILL BUILD IN TO THE NORTH OF THE SYSTEM AND DRIVE
IT ONTO A WESTWARD COURSE TOWARDS SOUTHERN CHINA. THE SYSTEM IS
FORECAST TO MAKE LANDFALL SOUTH OF ZHANJIANG AROUND TAU 30 AND
REEMERGE INTO THE GULF OF TONKIN BY TAU 36. DUE TO THE WEAKENED
STATE OF THE SYSTEM AFTER LANDFALL, THE TRACK WILL COME UNDER THE
INFLUENCE OF THE SYNOPTIC LOW LEVEL FLOW, LEADING TO A TURN
SOUTHWESTWARD TOWARDS CENTRAL VIETNAM THROUGH TAU 72. TY 24W IS
EXPECTED TO INTENSIFY SLIGHTLY OVER THE NEXT 12 HOURS, REACHING A
PEAK INTENSITY OF 75 KNOTS, AS THE ENVIRONMENT REMAINS FAVORABLE
FOR INTENSIFICATION. THE SYSTEM WILL THEREAFTER BEGIN A GRADUAL
WEAKENING TREND BEFORE LANDFALL AS IT ENCOUNTERS INCREASING VWS,
DECREASING SSTS AND DECREASED EXHAUST DUE TO UPPER-LEVEL MASS
CONVERGENCE ALOFT. INTERACTION WITH THE LAND AFTER TAU 24 WILL
INCREASE THE RATE OF WEAKENING, AND THE SYSTEM IS EXPECTED TO
REEMERGE IN THE GULF OF TONKIN AS A WEAK TROPICAL STORM. THE HIGH
SSTS IN THE GULF OF TONKIN WILL BE OFFSET BY HIGH VWS AND WEAK TO
NO EXHAUST, LEADING TO FURTHER WEAKENING BEFORE MAKING A SECOND
LANDFALL IN CENTRAL VIETNAM AS A TROPICAL DEPRESSION NEAR TAU 72.
NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT AND THERE IS HIGH
CONFIDENCE IN THE JTWC TRACK FORECAST.
     C. NEAR TAU 72, TY KHANUN WILL MAKE LANDFALL OVER CENTRAL
VIETNAM THEN QUICKLY DISSIPATE DUE TO INTERACTION WITH RUGGED
TERRAIN. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH THE
EXTENDED PORTION OF THE FORECAST, WITH SOME INCREASED MODEL SPREAD
BEYOND TAU 72 AS THE SYSTEM WEAKENS AND THE MODELS LOSE THE VORTEX.
OVERALL THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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