Tropical Storm NANGKA Advisory 10月14日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (NANGKA)
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 18W (NANGKA), LOCATED APPROXIMATELY 183 NM
EAST-SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT
17 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS THE SYSTEM HAS ACCELERATED THROUGH THE
ISLAND OF HAINAN AND EXITED INTO THE GULF OF TONKIN WITH MINOR
DEGRADATION. CONVECTION WRAPPING INTO A DEFINED LOW LEVEL
CIRCULATION (LLC) HAS QUICKLY RESUMED ALTHOUGH THE MAIN FEEDER BAND
HAS SEVERED AND REMAINED IN THE SOUTH CHINA SEA. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE LLC FEATURES IN
THE EIR LOOP AND A COMPOSITE RADAR LOOP FROM CNA. THE INITIAL
INTENSITY OF 45KTS IS BASED ON THE HIGH END OF AGENCY DVORAK
ESTIMATES OF T2.5/35KTS TO T3.0/45KTS. ENVIRONMENTAL ANALYSIS
INDICATES THE SYSTEM IS IN A GENERALLY FAVORABLE ENVIRONMENT WITH
LOW (10-15KT) VERTICAL WIND SHEAR, DIVERGENT WESTWARD OUTFLOW, AND
WARM (30C) SST. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY
OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS NANGKA WILL TRACK WESTWARD UNDER THE STR THROUGH THE GULF
OF TONKIN AND MAKE A FINAL LANDFALL OVER NORTHERN VIETNAM NEAR TAU
18. THE FAVORABLE ENVIRONMENT WILL FUEL A SECONDARY PEAK TO 50KTS BY
TAU 12; AFTERWARD, LAND INTERACTION WILL RAPIDLY ERODE THE SYSTEM TO
DISSIPATION BY TAU 36 AFTER IT DRAGS ACROSS THE RUGGED TERRAIN OF
VIETNAM AND LAOS. NUMERICAL MODELS REMAIN IN TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST.//
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