Tropical Storm KHANUN Advisory dom, 15.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KHANUN)
WARNING NR 12//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (KHANUN), LOCATED APPROXIMATELY 149 NM SOUTH-
SOUTHEAST OF HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
INDICATES THAT THE SYSTEM HAS CONTINUED TO CONSOLIDATE OVER THE
PAST SIX HOURS. SEVERAL CONSECUTIVE MICROWAVE PASSES SHOW A SMALL
BUT CLEAR MICROWAVE EYE FEATURE, INDICATING THE SYSTEM HAS
CONTINUED TO STRENGTHEN. THE MICROWAVE EYE IS NOT EVIDENT IN THE
VISIBLE IMAGERY, THOUGH THERE ARE HINTS OF A WARM SPOT IN THE
INFRARED IMAGERY. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON A 142238Z SSMIS 89GHZ MICROWAVE IMAGE WITH A
SMALL SYMMETRIC EYE. THE INITIAL INTENSITY IS SET AT 75 KNOTS BASED
ON ANALYSIS OF MULTI-AGENCY SUBJECTIVE DVORAK INTENSITY ESTIMATES
OF T4.5 (77 KNOTS) FROM PGTW AND T5.0 FROM RJTD (75 KNOTS) AS WELL
AS AUTOMATED DVORAK TECHNIQUE (ADT) ESTIMATES OF T4.7 (79 KNOTS).
ENVIRONMENTAL ANALYSIS SHOWS THAT TY 24W REMAINS IN A FAVORABLE
ENVIRONMENT, CONDUCIVE FOR FURTHER INTENSIFICATION. VERTICAL WIND
SHEAR (VWS) REMAINS IN THE MODERATE RANGE (15-20 KNOTS) BUT THE
STORM MOTION IS IN PHASE WITH THE SHEAR VECTOR, RESULTING IN A
LOWER RELATIVE SHEAR VALUE. OUTFLOW IS MARGINAL, WITH ONLY THE MAIN
OUTLET BEING TOWARDS THE SOUTHWEST. SEA SURFACE TEMPERATURES ARE
28-29 DEG CELSIUS AND FAVORABLE FOR SYSTEM DEVELOPMENT. TY 24W HAS
TURNED MORE WESTERLY OVER THE PAST SIX HOURS AND 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 ON A BROAD, CURVING TRACK
GENERALLY WESTWARD THROUGH TAU 24 UNDER THE INFLUENCE OF A DEEP
LAYER SUBTROPICAL RIDGE (STR) WHICH EXTENDS FROM TAIWAN TO MYANMAR.
TY 24W IS FORECAST TO MAKE LANDFALL SOUTH OF ZHANJIANG, CHINA NEAR
TAU 30 AND REEMERGE INTO THE GULF OF TONKIN BY TAU 36 AS A WEAK
TYPHOON. AFTER REEMERGENCE, THE SYSTEM WILL REMAIN UNDER THE
STEERING INFLUENCE OF THE STR, BUT AS THE AXIS OF THE RIDGE
REORIENTS, TY 24W WILL TURN SOUTHWESTWARD AND TRACK TOWARDS THE
CENTRAL COAST OF VIETNAM. TY 24W IS EXPECTED TO INTENSIFY SLIGHTLY
THROUGH TAU 12, AS THE ENVIRONMENT REMAINS FAVORABLE FOR
INTENSIFICATION AND IS EXPECTED TO PEAK AT 80 KNOTS. THEREAFTER,
THE SYSTEM WILL START TO WEAKEN, BOTH AS IT INTERACTS WITH LAND
OVER SOUTHERN CHINA, BUT ALSO IN RESPONSE TO INCREASING VWS AND
DECREASED OUTFLOW DUE TO UPPER-LEVEL MASS CONVERGENCE ALOFT. THE
RATE OF WEAKENING WILL INCREASE AS THE SYSTEM TURNS SOUTHWARD IN
THE GULF OF TONKIN AS VWS CONTINUES TO INCREASE AND THE SYSTEM
LOSES ITS UPPER LEVEL OUTFLOW MECHANISM. TY 24W IS EXPECTED TO MAKE
A SECOND LANDFALL ALONG THE CENTRAL VIETNAM COAST AROUND TAU 60 AND
RAPIDLY WEAKEN ONCE INLAND DUE TO TERRAIN EFFECTS. NUMERICAL MODEL
GUIDANCE IS IN GOOD AGREEMENT AND THERE IS HIGH CONFIDENCE IN THE
JTWC TRACK FORECAST.
     C. BEYOND TAU 72, THE SYSTEM WILL RAPIDLY DISSIPATE OVER THE
RUGGED TERRAIN OF SOUTHERN LAOS AND EASTERN THAILAND AND FULLY
DISSIPATE BY TAU 96. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT IN
THE LATER PORTION OF THE FORECAST WITH MOST MODELS LOSING THE
VORTEX. HOWEVER, THERE IS OVERALL HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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