Tropical Storm WIPHA Advisory Qua, 31-07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (WIPHA)
WARNING NR 02//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 08W (WIPHA), LOCATED APPROXIMATELY 234
NM SOUTH-SOUTHWEST OF HONG KONG, HAS TRACKED NORTHWESTWARD AT 06
KNOTS (KTS) OVER THE PAST SIX HOURS. THERE IS FAIR CONFIDENCE IN THE
INITIAL POSITION BASED ON A FULLY EXPOSED, BUT POORLY-DEFINED, LOW
LEVEL CIRCULATION CENTER (LLCC) IN ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI). THE MSI ALSO REVEALS THAT THE OVERALL CONVECTIVE
SIGNATURE HAS IMPROVED SLIGHTLY, WITH MORE DEEP CONVECTION IN THE
WESTERN QUADRANT, BUT THE SYSTEM STILL LACKS CENTRAL CONVECTION. THE
INITIAL INTENSITY IS BEING HELD AT 30 KTS AS THE OVERALL MSI
SIGNATURE IS JUST STARTING TO SHOW SIGNS OF IMPROVEMENT AND DVORAK
INTENSITY ESTIMATES REMAIN AT T1.5 (25 KTS) AND BELOW. ENVIRONMENTAL
CONDITIONS ARE SOMEWHAT FAVORABLE WITH GOOD EQUATORWARD OUTFLOW,
WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE, AND LOW (10-15 KT)
VERTICAL WIND SHEAR. A WEAK UPPER LEVEL LOW JUST NORTH OF THE SYSTEM
IS PROVIDING SUBSIDENCE AND INHIBITING INTENSIFICATION. TD 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. THROUGH TAU 72, TD 08W IS EXPECTED TO CONTINUE TRACKING ALONG
THE PERIPHERY OF THE STR, PASS OVER THE LEIZHOU PENINSULA AROUND TAU
30, ENTER THE GULF OF TONKIN NEAR TAU 36, AND MAKE LANDFALL NEAR
HANOI AROUND TAU 72. THE SUBSIDENCE FROM THE UPPER LEVEL LOW TO THE
NORTH IS EXPECTED TO LIMIT INTENSIFICATION TO A PEAK OF 35 KTS AT
TAU 12. BY TAU 24, THE UPPER LEVEL LOW SHOULD FILL BUT, BY THAT
TIME, LAND INTERACTION WILL INHIBIT INTENSIFICATION. THE JTWC TRACK
FORECAST FOLLOWS THE CONSENSUS THROUGH TAU 72. BASED ON SPREAD IN
THE NUMERICAL MODEL GUIDANCE BEING ABOUT 185 NM AT TAU 72 (PRIMARILY
DUE TO DIFFERENCES IN ALONG-TRACK SPEED), THERE IS LOW CONFIDENCE
FOR THIS PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, TD 08W WILL CONTINUE INLAND AND DISSIPATE. THE
JTWC TRACK FORECAST FOLLOWS CONSENSUS WITH LOW CONFIDENCE BASED ON
LARGE SPREAD IN THE MODEL GUIDANCE.//
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