Tropical Storm GAEMI Advisory Sat Oct 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (GAEMI) WARNING NR
19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 21W (GAEMI), LOCATED APPROXIMATELY 330 NM
EAST-NORTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED
SATELLITE IMAGERY INDICATES THAT TS 21W HAS INTENSIFIED SLIGHTLY
OVER THE PAST SIX HOURS WITH A LARGE AREA OF DEEP CONVECTION NOW
CONCEALING THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE BULK OF THIS
DEEP CONVECTION REMAINS CONFINED TO THE WESTERN SEMI-CIRCLE DUE TO
MODERATE (20-25 KNOTS) EASTERLY VERTICAL WIND SHEAR (VWS). RECENT
MICROWAVE IMAGERY INCLUDING A 062202Z SSMIS SHOWS IMPROVED
CONVECTIVE BANDING BUT SUGGESTS THE CENTER IS POSITIONED ALONG THE
EASTERN EDGE OF THE DEEP CONVECTION. DUE TO THE INCREASE IN
CONVECTION OVER THE LLCC, THERE IS DECREASING CONFIDENCE IN THE
INITIAL POSITION. THE INITIAL INTENSITY WAS ASSESSED
AT 40 KNOTS BASED ON AN AVERAGE OF DVORAK ESTIMATES RANGING FROM 35
TO 45 KNOTS AND IS CONSISTENT WITH OBJECTIVE DVORAK ESTIMATES
RANGING FROM 40 TO 45 KNOTS. TS 21W IS TRACKING WESTWARD UNDER THE
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 21W WILL CONTINUE TRACKING WESTWARD THROUGH THE FORECAST
PERIOD AND WILL MAKE LANDFALL ALONG THE EAST COAST OF VIETNAM BY TAU
12. AFTER TAU 12, GAEMI IS FORECAST TO DISSIPATE DUE TO LAND
INTERACTION. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT,
THEREFORE, THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK. TS 21W IS
FORECAST TO INTENSIFY SLIGHTLY TO A PEAK OF 45 KNOTS PRIOR TO
LANDFALL AS THE EASTERLY VWS IS OFFSET SOMEWHAT BY THE QUICK
WESTWARD TRACK.//
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