Tropical Storm KAI-TAK Advisory Tue Aug 14

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (KAI-TAK) WARNING
NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 14W (KAI-TAK), LOCATED APPROXIMATELY 220 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED SOUTHWESTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY (EIR) SHOWS THE CENTRAL DENSE OVERCAST CONVECTION APPEARS TO
BE BUILDING NORTHWARD OVER THE LOW LEVEL CIRCULATION CENTER (LLCC)
WITHIN THE PAST SIX HOURS. ADDITIONALLY, IN OLDER MULTISPECTRAL
IMAGERY, THE LLCC HAD BEGUN TO TURN SOUTHWESTWARD AND APPEARS TO
PERSIST IN THE EIR AS WELL. THIS APPEARS TO BE IN PART DUE TO A
CONSOLIDATION OF THE LOW LEVEL TO A MORE SYMMETRICALLY ORGANIZED
LLCC. THE CURRENT POSITION IS BASED ON A CONSOLIDATION OF POSITION
FIXES FROM PGTW AND RJTD AND IS SUPPORTED BY A RECENT 141129Z SSMIS
91 GHZ IMAGE. UPPER LEVEL ANALYSIS INDICATES A POINT SOURCE
ANTICYCLONE LOCATED TO THE NORTHEAST OF TS 14W PERSISTS IN CREATING
15 TO 20 KNOTS OF VERTICAL WIND SHEAR (VWS) OVER THE LLCC. THE VWS
IS PROVIDING AN AMPLE EQUATORWARD OUTFLOW CHANNEL. THE CURRENT
INTENSITY HAS BEEN INCREASED TO 50 KNOTS BASED ON THE IMPROVING
DVORAK ESTIMATES FROM PGTW AND IS SUPPORTED BY THE INCREASING
CENTRAL CONVECTION AND COOLING CLOUD TOPS OBSERVED IN EIR. TS 14W IS
BEING STEERED IN A GENERAL WEST-NORTHWESTWARD DIRECTION UNDER THE
INFLUENCE OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) CENTERED FAR
TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 14W IS FORECASTED TO TRACK WEST-NORTHWESTWARD UNDER THE
INFLUENCE OF THE STR THROUGHOUT THE FORECAST PERIOD. DUE TO THE
RECENT SOUTHWESTWARD TRACK OF THE LLCC, THIS FORECAST BRINGS THE
OVERALL TRACK SOUTHWARD SLIGHTLY. THE FORECAST IS SLIGHTLY SOUTH OF
CONSENSUS, AS THE RECENT DIP WAS NOT PREVIOUSLY INDICATED WITHIN
MODEL GUIDANCE, THROUGH TAU 48. A SERIES OF WEAK MID-LATITUDE
TROUGHS ARE EXPECTED TO SLIGHTLY WEAKEN THE STR OVER THE NEXT 36
HOURS, BUT WILL NOT CREATE A FULL BREAK WITHIN THE STR. THIS
WEAKENING EXPLAINS THE MODEL GUIDANCE SHOWING THE SHIFT IN THE TRACK
TO THE WEST-NORTHWESTWARD. BEYOND TAU 36, THE TROUGHS WILL TRACK
RAPIDLY EASTWARD ALLOWING THE STR TO BUILD BACK IN OVER EASTERN
CHINA. GRADUAL INTENSIFICATION AFTER TAU 12 IS EXPECTED AS THE
SYSTEM TRACKS OVER LUZON INTO THE SOUTH CHINA SEA. DUE TO THE
COMPETING INFLUENCES OF VERY WARM ALONG TRACK SEA SURFACE
TEMPERATURES (SST) (28-30 DEGREES CELSIUS) AND MODERATE VWS, ONCE TS
14W MOVES BACK OVER WATER, THE EXPECTED INTENSIFICATION RATE WILL
REMAIN SLOW. THE FORECASTED MAXIMUM INTENSITY OF 65 KNOTS AT TAU 48
DOES NOT REFLECT THE EXPECTED MAXIMUM INTENSITY OF ABOUT 70 TO 75
KNOTS AROUND TAU 60 SLIGHTLY BEFORE MAKING LANDFALL TO THE EAST OF
HONG KONG. A VERY WARM POOL OF SSTS ALONG THE COASTAL REGION ARE
EXPECTED TO FURTHER INTENSIFY THE SYSTEM BETWEEN TAU 48 AND 60. THE
TIMING OF LANDFALL REMAINS BETWEEN TAU 48 AND 72 WITH FRICTIONAL
LAND INFLUENCES QUICKLY WEAKENING THE LLCC UPON LANDFALL.
   C. AFTER TAU 72 TS 14W WILL CONTINUE TO WEAKEN UNDER THE
INFLUENCE OF FRICTIONAL DRAG AND THE LOSS OF THE OCEAN HEATING LINK.
NUMERICAL MODEL GUIDANCE REMAINS IN FAIR AGREEMENT THROUGH TAU 48,
WITH NGPS AND WBAR BEING THE NORTHERN OUTLIERS. ECMWF, GFS, AND GFDN
ARE THE SOUTHERN OUTLIERS, AND ARE IN BETTER AGREEMENT WITH THE
OFFICIAL FORECAST. ALTHOUGH THERE IS LOW CONFIDENCE IN THE CURRENT
POSITION, THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK BASED ON
ANALYSIS OF THE SYNOPTIC ENVIRONMENT AND NUMERICAL MODELS SHOWING A
SIMILAR PICTURE WITH ONLY SLIGHT VARIATIONS IN THE AMOUNT OF
WEAKENING DEPICTED FOR THE STR.//
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