Tropical Storm WIPHA Advisory Fri Aug 02

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (WIPHA)
WARNING NR 07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 08W (WIPHA), LOCATED APPROXIMATELY 287 NM
EAST OF HANOI, VIETNAM, HAS TRACKED NORTH-NORTHWESTWARD AT 05 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS A COMPACT, WELL-DEFINED LOW-LEVEL CIRCULATION CENTER
(LLCC) WITH FRAGMENTED DEEP CONVECTIVE BANDING. A 010530Z AMSR2
89GHZ IMAGE DEPICTS SHALLOW BANDING WRAPPING INTO A WELL-DEFINED
LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. A
010245Z ASCAT IMAGE REVEALS A DEFINED CENTER WITH 30 TO 35 KNOT
WINDS OVER THE SOUTH AND EAST QUADRANTS, WHICH SUPPORTS THE INITIAL
INTENSITY ASSESSMENT OF 35 KNOTS. THE ASCAT AMBIGUITY ANALYSIS,
AMSR2 IMAGE, MSI AND A 010716Z GPM 89GHZ IMAGE ALL PROVIDE EVIDENCE
OF AN ABRUPT NORTH-NORTHWESTWARD TURN OVER THE PAST 5-6 HOURS, WHICH
HAS ALLOWED THE SYSTEM TO REMAIN OVER FAVORABLE SST (28-29C) WITH AN
IMPROVED CONVECTIVE SIGNATURE. HOWEVER, THE SYSTEM IS STILL EXPECTED
TO TURN GRADUALLY WESTWARD OVER THE NEXT 12 TO 24 HOURS. 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 POSITIONED WEST AND SOUTH OF A LOW- TO MID-LEVEL
SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 08W HAS TRACKED NORTH-NORTHWESTWARD IN THE SHORT-TERM DUE
TO AN EXTENSION OF THE STR TO THE EAST, HOWEVER, THE SYSTEM WILL
GRADUALLY TURN WESTWARD AS IT TRACKS UNDER THE DOMINANT STEERING
INFLUENCE OF THE STR ENTRENCHED TO THE NORTH. THERE IS SOME
UNCERTAINTY IN THE TIMING OF THIS INEVITABLE WESTWARD TURN, WHICH
INTRODUCES SOME 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 42 AND DISSIPATION BY TAU 48 NEAR HANOI.
DYNAMIC MODEL GUIDANCE REFLECTS THIS UNCERTAINTY WITH SOME SOLUTIONS
FURTHER NORTH OVER THE COAST, WHICH COULD LEAD TO GREATER WEAKENING.
DUE TO THIS UNCERTAINTY, THERE IS MODERATE CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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