Tropical Storm MEKKHALA Advisory Seg, 10-08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (SEVEN) WARNING
NR 003//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 07W (SEVEN), LOCATED APPROXIMATELY 305 NM
SOUTHEAST OF HONG KONG, HAS TRACKED NORTHWARD AT 09 KNOTS OVER THE
PAST SIX HOURS. THE CURRENT POSITION IS SITUATED DOWNSTREAM FROM A
CENTER FEATURE EVIDENT IN 092233Z SSMIS IMAGERY AND NEAR SATELLITE
POSITION FIXES FROM PGTW AND RJTD. THE INTENSITY OF 35 KNOTS IS
BASED ON A CONSENSUS OF RECENT SUBJECTIVE DVORAK AND AUTOMATED
INTENSITY ESTIMATES FROM MULTIPLE REPORTING AGENCIES, AND A 100031Z
METOP-A ASCAT PASS SHOWING AN AREA OF 35 KNOT WINDS WITHIN THE
SOUTHERN PORTION OF THE LOW-LEVEL CIRCULATION. DEEP CONVECTION HAS
INCREASED OVER THE CIRCULATION AND CONVECTIVE BANDING HAS BECOME
MORE DEFINED OVER THE PAST SIX HOURS. TS 07W IS TRACKING POLEWARD
ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL STEERING RIDGE (STR)
EXTENSION. THE SYSTEM IS SITUATED IN AN AREA OF MODERATE (15-20 KTS)
VERTICAL WIND SHEAR AND VERY WARM (29-30C) SEA SURFACE TEMPERATURES.
UPPER-LEVEL DIFFLUENCE IS LIMITED, BUT AN ANALYSIS OF SATELLITE-
DERIVED ATMOSPHERIC MOTION VECTORS SUGGESTS THAT SOUTHWESTWARD
OUTFLOW IS INCREASING.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 07W WILL CONTINUE TO TRACK POLEWARD ALONG THE STR THROUGH
THE FORECAST PERIOD, MAKING LANDFALL IN SOUTHEASTERN CHINA JUST
AFTER TAU 24. STEADY INTENSIFICATION IS ANTICIPATED PRIOR TO
LANDFALL, DESPITE PERSISTENT VERTICAL WIND SHEAR, DUE TO CONTINUED
PASSAGE OVER VERY WARM WATER AND INCREASING POLEWARD OUTFLOW AIDED
BY AN UPPER-LEVEL TROUGH TO THE NORTHEAST. AFTER THE SYSTEM MAKES
LANDFALL, IT WILL WEAKEN DUE TO THE FRICTIONAL EFFECTS OF LAND AND
DISSIPATE BY TAU 48. NUMERICAL MODEL FORECASTS ARE IN GOOD AGREEMENT
REGARDING THE OVERALL FORECAST SCENARIO, BUT THERE IS SOME SPREAD IN
THE EXACT DIRECTION AND SPEED OF MOVEMENT. OVERALL, THERE IS FAIR
CONFIDENCE IN JTWC TRACK FORECAST.//
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