Tropical Storm BOLAVEN Advisory 1月4日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (BOLAVEN)
WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 01W (BOLAVEN), LOCATED APPROXIMATELY 305 NM
EAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WESTWARD AT 15 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS
FLARING CONVECTION TO THE NORTH OF A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC). A 031349Z 89GHZ AMSU MICROWAVE IMAGE
SHOWS A SMALL AREA OF DEEP CONVECTION TO THE NORTHWEST OF THE LLCC.
THE IMAGE ALSO DEPICTS WEAK BANDING FEATURES WRAPPING INTO THE LLCC
FROM THE EASTERN SEMI-CIRCLE. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON EXTRAPOLATION FROM THE AFOREMENTIONED
MICROWAVE IMAGE AND THE PARTIALLY EXPOSED LLCC. THE INITIAL
INTENSITY IS HEDGED ON THE UPPER END OF MUTLI-AGENCY DVORAK CURRENT
INTENSITY ESTIMATES RANGING FROM T1.0 TO T2.0 (25-30 KNOTS) FROM
PGTW AND RJTD RESPECTIVELY. ENVIRONMENTAL ANALYSIS INDICATES A
MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (15 TO 20
KNOTS) VERTICAL WIND SHEAR (VWS) AND WARM (26-27 CELSIUS) SEA
SURFACE TEMPERATURES. UPPER LEVEL ANALYSIS REVEALS BROAD DIFFLUENCE
ALOFT WITH NO DEFINED OUTFLOW CHANNELS. TD 01W IS TRACKING WESTWARD
UNDER THE INFLUENCE OF AN EAST-WEST ORIENTED SUBTROPICAL STEERING
RIDGE (STR) LOCATED TO THE NORTHEAST.
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 WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE STR. THE SYSTEM WILL CONTINUE TO WEAKEN IN
A MARGINALLY FAVORABLE ENVIRONMENT, EVENTUALLY MAKING LANDFALL NORTH
OF HO CHI MINH CITY, VIETNAM AROUND TAU 12. AFTER LANDFALL, THE
SYSTEM WILL DISSIPATE RAPIDLY AS IT TRACKS INLAND THROUGH THE RUGGED
TERRAIN OF SOUTHERN VIETNAM. NUMERICAL MODEL GUIDANCE REMAINS IN
FAIR AGREEMENT THROUGH TAU 12 WITH A GENERALLY WESTERN TRACK. AFTER
TAU 12, THERE IS SIGNIFICANT SPREADING IN MODEL GUIDANCE WITH NAVGEM
BEING THE PRINCIPLE OUTLIER, PRODUCING A NORTHWESTERN TRACK
SOLUTION. 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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