Tropical Storm WIPHA Advisory so., 31.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (WIPHA)
WARNING NR 05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 08W (WIPHA), LOCATED APPROXIMATELY 313 NM EAST OF
HANOI, VIETNAM, HAS TRACKED NORTHWESTWARD AT 05 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY SHOWS A LARGE AREA OF
FRAGMENTED AND POORLY ORGANIZED DEEP CONVECTION WITH MONSOON
DEPRESSION CHARACTERISTICS. THE MAIN BANDS ARE FEEDING IN FROM THE
SOUTH INTO A BROAD, ELONGATED AND ASYMMETRICAL LOW LEVEL CIRCULATION
(LLC). THE INITIAL POSITION AND INTENSITY ARE EXTRAPOLATED FROM A
311415Z DIRECT ASCAT PASS SHOWING MULTIPLE 35-KNOT WIND BARBS ALONG
THE NORTHWEST PERIPHERY OF THE LLC. THE INTENSITY IS HELD SLIGHTLY
HIGHER THAN RJTD AND PGTW DVORAK ESTIMATES BUT CONSISTENT WITH THE
311800Z T2.5/35KTS FIX FROM RCTP. UPPER LEVEL ANALYSIS INDICATES AN
EASTWARD OUTFLOW CHANNEL TOWARD A TUTT CELL ANCHORED OVER OKINAWA
THAT IS PROVIDING VENTILATION TO THE FLARING CONVECTION. HOWEVER,
THIS IS OFFSET BY A MODERATE (15-20 KNOT) EASTERLY VERTICAL WIND
SHEAR (VWS). TS 08W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS WIPHA IS EXPECTED TO REMAIN ON ITS CURRENT TRACK THROUGHOUT
THE FORECAST, MAKING LANDFALL OVER THE LEIZHOU PENINSULA SHORTLY
AFTER TAU 12. AFTERWARD, IT WILL CROSS THE GULF OF TONKIN MOMENTARILY
BEFORE MAKING A FINAL LANDFALL IN SOUTH CHINA NEAR BEIHAI. LAND
INTERACTION, IN ADDITION TO THE MODERATE VWS, WILL RAPIDLY ERODE THE
SYSTEM, LEADING TO DISSIPATION BY TAU 36. THERE IS A SMALL
PROBABILITY THAT TS 08W WILL TRACK MORE WESTWARD RESULTING IN A
LONGER DRIFT OVER THE GULF OF TONKIN, HENCE, A LONGER LIFESPAN.
AVAILABLE NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH SOME SPREADING
AFTER TAU 24, LENDING FAIR CONFIDENCE IN THE JTWC TRACK FORECAST.  //
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