Tropical Storm WIPHA Advisory 8月2日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (WIPHA)
WARNING NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 08W (WIPHA), LOCATED APPROXIMATELY 197 NM
EAST OF HANOI, VIETNAM, HAS TRACKED WESTWARD AT 08 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
SHOWS THE SYSTEM HAS DEGRADED AS IT TRACKED ACROSS THE LEIZHOU
PENINSULA AND INTO THE GULF OF TONKIN. THE ASSOCIATED CONVECTION HAVE
BEGUN TO COLLAPSE AS EVIDENCED BY WARMING TOPS, AND UNRAVEL. HOWEVER,
THE LOW LEVEL CIRCULATION CENTER (LLCC) REMAINS INTACT, BASED ON A
COMPOSITE RADAR LOOP FROM CHINA. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE RADAR LOOP AND FROM NEARBY SURFACE
OBSERVATIONS, INCLUDING THOSE FROM BEHAI, 15 NM NORTHWEST OF THE
LLCC. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE
ENVIRONMENT WITH LOW TO MODERATE VERTICAL WIND SHEAR OFFSET BY GOOD
POLEWARD AND EQUATORWARD OUTFLOW. TS 08W IS TRACKING UNDER THE
STEERING INFLUENCE OF THE LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR)
TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 08W WILL GRADUALLY TURN WESTWARD TO WEST-SOUTHWESTWARD AS
IT TRACKS UNDER THE STR. THERE IS UNCERTAINTY IN THE TIMING OF
THIS WESTWARD TURN, WHICH ALSO INTRODUCES UNCERTAINTY IN THE
INTENSITY
FORECAST AND EXACT TRACK OVER THE GULF OF TONKIN. THE CURRENT JTWC
FORECAST TRACK SKIRTS THE SOUTHERN COAST OF CHINA WITH LANDFALL
ALONG THE NORTHEAST COAST OF VIETNAM NEAR TAU 18 AND DISSIPATION BY
TAU 36 EAST OF HANOI. DYNAMIC MODEL GUIDANCE REFLECTS THIS
UNCERTAINTY
WITH SOME SOLUTIONS FURTHER SOUTH OVER WATER, WHICH COULD LEAD TO A
PROLONGED LIFESPAN. DUE TO THIS UNCERTAINTY, THERE IS LOW CONFIDENCE
IN THE JTWC FORECAST TRACK.//
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