Tropical Storm BOLAVEN Advisory jue, 04-01

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (BOLAVEN)
WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 01W (BOLAVEN), LOCATED APPROXIMATELY 477
NM EAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED NORTHWESTWARD AT 13
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER
(LLCC) POSITIONED ON THE SOUTHEASTERN EDGE OF AN AREA OF
DISORGANIZED, PERSISTENT DEEP CONVECTION. A 030600Z HIMAWARI VISIBLE
SATELLITE IMAGE SHOWS THE AFOREMENTIONED LLCC WITH CONVECTION LOCATED
TO THE NORTHWEST. UPPER-LEVEL ANALYSIS INDICATES A MARGINAL
ENVIRONMENT WITH LOW TO MODERATE (15 TO 20 KNOTS) VERTICAL WIND SHEAR
(VWS) AND BROAD DIFFLUENCE. THE INITIAL INTENSITY ASSESSMENT REMAINS
AT 30 KNOTS BASED ON AN RJTD DVORAK ESTIMATE OF T2.0 (30 KNOTS). SEA
SURFACE TEMPERATURES REMAIN FAVORABLE, NEAR 27 DEGREES CELSIUS. TD
01W IS TRACKING WESTWARD UNDER THE STEERING INFLUENCE OF AN EAST-WEST
ORIENTED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 01W IS FORECAST TO TRACK WESTWARD TO WEST-NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR WHICH IS LOCATED TO THE NORTH
AND SHOULD MAINTAIN INTENSITY AT 30 KNOTS THROUGH TAU 12. AFTER TAU
12, TD 01W WILL WEAKEN GRADUALLY DUE TO PERSISTENT VWS AND COOLER SEA
SURFACE TEMPERATURES AS IT APPROACHES VIETNAM. TD 01W IS FORECAST TO
MAKE LANDFALL SHORTLY AFTER TAU 24. THE SYSTEM IS EXPECTED TO
DISSIPATE RAPIDLY AS IT TRACKS INLAND. NUMERICAL MODEL GUIDANCE
REMAINS IN FAIR AGREEMENT THROUGH TAU 12 WITH INCREASED SPREADING IN
MODEL GUIDANCE BEYOND TAU 12. OVERALL, THERE IS LOW CONFIDENCE IN THE
JTWC FORECAST TRACK DUE TO THE LARGE SPREAD IN MODEL SOLUTIONS AFTER
TAU 12.//
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