Tropical Storm KAI-TAK Advisory 12月19日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 32W (KAI-TAK)
WARNING NR 21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 32W (KAI-TAK), LOCATED APPROXIMATELY 547 NM
EAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-SOUTHWESTWARD
AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY SHOWS THE LOW LEVEL CIRCULATION CENTER (LLCC)
WITH SCATTERED CONVECTION FLARING AROUND IT. THE INITIAL POSITION
IS BASED ON A 190000Z HIMAWARI VISIBLE SATELLITE IMAGE SHOWING
DISSIPATING CONVECTION NORTH OF THE LLCC WITH INTENSIFYING
CONVECTION SOUTH OF THE LLCC. THE INITIAL INTENSITY ESTIMATE IS 35
KNOTS WHICH IS BASED ON AN 181420Z ASCAT METOP-B IMAGE WHICH SHOWS
THE WESTERN EXTENT OF THE TS 32W WIND FIELD. UPPER LEVEL ANALYSIS
SHOWS VERTICAL WIND SHEAR REMAINS MODERATE (15 TO 20 KNOTS), BUT
HAS IMPROVED SLIGHTLY OVER THE PAST SIX HOURS. POLEWARD OUTFLOW HAS
DECREASED IN INTENSITY AND IS NOW MODERATE. SEA SURFACE
TEMPERATURES REMAIN FAVORABLE (26 TO 27 DEGREES CELSIUS). TS 32W IS
TRACKING WEST-SOUTHWESTWARD UNDER THE INFLUENCE OF A SUBTROPICAL
RIDGE (STR) WHICH IS LOCATED TO THE NORTHWEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 32W WILL TRACK SOUTHWESTERLY FOR THE REMAINDER OF THE
FORECAST WHILE UNDER THE INFLUENCE OF THE BUILDING STR LOCATED TO
THE NORTHWEST. THE SOUTH CHINA SEA IS EXPERIENCING STRONG NORTHERLY
WINDS WHICH ARE ASSOCIATED WITH A SURGE EVENT. THE DIFFERENTIATION
BETWEEN THE SURGE WINDS AND THE OUTER EDGE OF TS 32W IS DIFFICULT
TO DETERMINE. REGARDLESS, IN THE VICINITY OF TS 32W THE SOUTH CHINA
SEA WILL CONTINUE TO EXPERIENCE WINDS NEAR 35 TO 40 KNOTS
ASSOCIATED WITH BOTH THE SURGE EVENT AND TS 32W. NUMERICAL MODEL
GUIDANCE IS INDICATING THAT A WARM CORE CIRCULATION WILL MAINTAIN
COHESION AS IT TRACKS SOUTHWESTERLY ACROSS THE SOUTH CHINA SEA.
INTENSITY WILL INCREASE SLIGHTLY TO 40 KNOTS BY TAU 12. TS 32W WILL
MAINTAIN 40 KNOT INTENSITY THROUGH TAU 48 BEFORE IT BEGINS TO
DISSIPATE.
   C. BEYOND TAU 72, TS 32W WILL CONTINUE TO TRACK SOUTHWESTWARD
UNDER THE INFLUENCE OF THE STR LOCATED TO THE NORTHWEST. VERTICAL
WIND SHEAR IS FORECAST TO INTENSIFY AND WEAKEN TS 32W AS IT TRACK
ACROSS THE SOUTH CHINA SEA. TS 32W WILL DISSIPATE BY TAU 96. MODELS
ARE STILL UNABLE TO DIFFERENTIATE THE SURGE EVENT WIND FIELD FROM
THE TS 32W WIND FIELD. DESPITE THESE DIFFERENCES THERE IS OVERALL
HIGH CONFIDENCE IN THE FORECAST TRACK.//
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