Tropical Storm PODUL Advisory 8月29日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (PODUL) WARNING NR
10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 13W (PODUL), LOCATED APPROXIMATELY 316 NM
EAST OF HUE, VIETNAM, HAS TRACKED WESTWARD AT 10 KNOTS (KTS) OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE (EIR) IMAGERY
SHOWS THE CENTRAL CONVECTION DISPLACED APPROXIMATELY 70NM
SOUTHWESTWARD OF THE PARTIALLY EXPOSED LOW LEVEL CIRCULATION (LLC).
THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LLC IN THE EIR LOOP AND MOSTLY CONCENTRIC WITH AN
LLC FEATURE IN A COMPOSITE RADAR REFLECTIVITY LOOP FROM CMA. THE
INITIAL INTENSITY OF 35 KNOTS IS BASED ON MULTI-AGENCY DVORAK
ESTIMATES OF T2.5/35KTS AND IS CONSISTENT WITH NEARBY SURFACE
OBSERVATIONS INCLUDING THOSE FROM XISHA DAO, APPROXIMATELY 72NM TO
THE WEST-SOUTHWEST. THE ENVIRONMENT IS MARGINAL AT BEST WITH
UNFAVORABLY STRONG (25-30 KT) VERTICAL WIND SHEAR (VWS) OFFSETTING
FAVORABLE WESTWARD OUTFLOW, IN-PHASE STORM MOTION, AND WARM SEA
SURFACE TEMPERATURES (29-30 CELSIUS). TS 13W IS TRACKING ALONG THE
SOUTHERN 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. TS 13W WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE STR UNTIL MAKING LANDFALL OVER NORTH
CENTRAL VIETNAM SHORTLY AFTER TAU 30. MARGINAL ENVIRONMENTAL
CONDITIONS WILL SUSTAIN THE INTENSITY UP TO 12 HOURS THEN GRADUALLY
WEAKEN PRIOR TO LANDFALL. AFTERWARD, THE SYSTEM WILL RAPIDLY ERODE
AND SHOULD DISSIPATE DUE TO LAND INTERACTION NO LATER THAN TAU 48.
MODEL GUIDANCE IS IN GOOD AGREEMENT WITH NAVGEM AS THE NOTABLE
RIGHT-OF-TRACK OUTLIER. THE JTWC TRACK FORECAST IS LAID WITH FAIR
CONFIDENCE JUST LEFT OF AND SLOWER THAN CONSENSUS TO OFFSET NAVGEMS
UNLIKELY POLEWARD TRACK TOWARD THE STR.//
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