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 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 08W (WIPHA), LOCATED APPROXIMATELY 185 NM
EAST OF HANOI, VIETNAM, HAS TRACKED SOUTHWESTWARD AT 01 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
CONTINUES TO SHOW A RELATIVELY UNIMPRESSIVE AND RAGGED SYSTEM WITH
SOME INCREASED DEEP CONVECTION BEGINNING TO DEVELOP NEAR THE
ASSESSED LOW LEVEL CENTER AS INDICATED BY OVERSHOOTING TOPS EVIDENT
IN THE EARLY MORNING MULTISPECTRAL IMAGERY. WHILE NOT EVIDENT IN THE
MULTISPECTRAL IMAGERY, LAND BASED RADAR COMPOSITES FROM CHINA
INDICATE A VERY WELL-DEFINED EYE FEATURE ASSOCIATED WITH THIS
SYSTEM, JUST OFFSHORE BEHAI, CHINA. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE RADAR LOOP AND NEARBY SURFACE
OBSERVATIONS, INCLUDING THOSE FROM BEHAI. A 012318Z SSMIS 89 GHZ
MICROWAVE IMAGE WITH A WEAK MICROWAVE EYE FEATURE LENDS SUPPORT TO
THE INITIAL POSITION AND SHOWS A BROAD BAND OF DEEP CONVECTION OVER
WATER TO THE SOUTH OF THE LLCC. UPPER-LEVEL ANALYSIS INDICATES A
MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (15-20 KNOTS)
VWS AND STRONG EQUATORWARD OUTFLOW. A WEAK POINT SOURCE APPEARS TO
HAVE DEVELOPED OVER THE TOP OF TS 08W, WHICH IS PROVIDING SOME
ADDITIONAL POLEWARD OUTFLOW ALONG THE WESTERN SIDE OF AN UPPER-LEVEL
ANTICYCLONE TO THE EAST NEAR HONG KONG. SSTS IN THE AREA OF 30-31
DEGREES CELSIUS ARE SUPPORTIVE FOR INTENSIFICATION. AFTER REEMERGING
INTO THE GULF OF TONKIN, FORWARD MOTION HAS SLOWED CONSIDERABLY,
WITH THE SYSTEM NOW BECOMING QUASI-STATIONARY WHILE MOVING THROUGH A
GENERALLY WEAK STEERING ENVIRONMENT BETWEEN A STR OVER EAST-CENTRAL
CHINA AND NER CENTERED NEAR THE NORTHERN STRAIT OF MALACCA.
3. FORECAST REASONING.
   A. WHILE THE OVERALL FORECAST PHILOSOPHY HAS NOT CHANGED, DUE TO
THE QUASI-STATIONARY MOTION IN THE NEAR-TERM, THE TRACK HAS BEEN
ADJUSTED TO REMAIN OVER WATER THROUGH TAU 48 AND THE FORECAST
EXTENDED TO TAU 72.
   B. OVER THE NEXT 24 HOURS, TS 08W WILL DRIFT SLOWLY SOUTHWESTWARD
UNDER THE INFLUENCE OF A WEAK STEERING ENVIRONMENT. BY TAU 24, AN
UPPER-LEVEL ANTICYCLONE WILL STRENGTHEN OVER SOUTHERN CHINA,
ALLOWING TS 08W TO ACCELERATE SLIGHTLY WHILE MAINTAINING AND OVERALL
SOUTHWESTWARD TRACK THROUGH TAU 48, PARALLEL TO THE VIETNAMESE
COASTLINE. THE SYSTEM IS FORECAST TO MAKE LANDFALL SOUTH OF HANOI
NEAR TAU 60. THE SYSTEM IS FORECAST TO INTENSIFY SLIGHTLY AS IT
REMAINS OVER VERY WARM (30-31 DEGREES CELSIUS) AND MAINTAINS ROBUST
EQUATORWARD AND WEAK POLEWARD OUTFLOW THROUGH TAU 24 WITH RELATIVELY
LOW VWS. THEREAFTER THE SYSTEM WILL GRADUALLY WEAKEN, AS THE OUTFLOW
GRADUALLY BECOMES LESS DIFFLUENT AND VWS INCREASES. DYNAMIC MODEL
GUIDANCE IS IN MODERATE AGREEMENT ON THE TRACK OF TS 08W, WITH THE
ECMWF SOLUTION TAKING THE SYSTEM INLAND MUCH SOONER AND CLOSER TO
HANOI, WHILE THE AFUM AND NAVGEM KEEP THE SYSTEM OVER WATER AND
FURTHER SOUTH. THE OFFICIAL JTWC FORECAST TRACK LIES JUST SOUTH OF
THE MULTI-MODEL CONSENSUS, BUT IS MUCH SLOWER IN LIGHT OF THE NEAR-
TERM QUASI-STATIONARY MOTION, LEADING TO A LONGER PERIOD OVER WATER
IN WHICH THE SYSTEM COULD INTENSIFY. DUE TO THIS UNCERTAINTY, THERE
IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK.//
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