Tropical Storm BOLAVEN Advisory mar, 28.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (BOLAVEN) WARNING
NR 33//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 16W (BOLAVEN), LOCATED APPROXIMATELY 200 NM
SOUTHWEST OF SEOUL, SOUTH KOREA, HAS TRACKED NORTHWARD AT 18 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS THE CONVECTION THAT HAD PREVIOUSLY BEEN COLLOCATED OVER THE
LOW LEVEL CIRCULATION CENTER (LLCC) HAS STARTED TO SEPARATE IN THE
PRESENCE OF INCREASING SOUTHWESTWARD VERTICAL WIND SHEAR (VWS). THE
LLCC ITSELF APPEARS TO BE PARTIALLY EXPOSED ON THE SOUTHWESTERN
QUADRANT OF THE DEEPEST CONVECTION BUT REMAINS OBSCURED BY A FEW
BANDS OF WEAKER CONVECTION WRAPPING INTO THE DEEPER CONVECTION. THE
CURRENT INTENSITY OF 55 KNOTS IS BASED ON A 3.0/3.5 DVORAK FROM
PGTW, WHICH INDICATES THE LLCC IS WEAKENING MORE RAPIDLY THAN
PREVIOUSLY FORECAST. RJTD IS SLIGHTLY HIGHER AT A 3.5/4.0, BUT IS
ALSO INDICATING A WEAKENING TREND OVER THE PAST 12 HOURS. UPPER
LEVEL ANALYSIS REVEALS THAT TS 16W IS NORTH OF AN UPPER LEVEL
SUBTROPICAL RIDGE (STR) AXIS, WHICH IS CREATING THE HIGH LEVELS OF
VWS (20 TO 30 KNOTS) NOTED EARLIER. TS 16W CONTINUES TO TRACK ALONG
THE WESTERN PERIPHERY OF A DEEP STR CENTERED OVER CENTRAL JAPAN.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 16W IS FORECAST TO CONTINUE TRACKING NORTHWARD ALONG THE
WESTERN EDGE OF THE STR THROUGH TAU 12, AND ACCELERATING AHEAD OF A
DEEP UPPER-LEVEL TROUGH DIGGING OVER EASTERN CHINA. BASED ON THE
RECENT INCREASE IN TRACK SPEED, TS 16W IS EXPECTED TO MAKE LANDFALL
ALONG THE WESTERN COAST OF NORTH KOREA BY TAU 12. THE INTENSITY WILL
REMAIN ON A STEADY DECLINE IN THE PRESENCE OF A DECREASINGLY
FAVORABLE ENVIRONMENT (INCREASED VWS, DECREASED SEA SURFACE
TEMPERATURES, AND LAND INTERACTION). IN LIGHT OF THE INCREASING VWS
AND INTERACTION WITH AN APPROACHING MID-LATITUDE LOW FROM THE WEST,
EXTRATROPICAL TRANSITION HAS STARTED AND IS EXPECTED TO COMPLETE BY
TAU 36. THERE IS HIGH CONFIDENCE IN THE TRACK FORECAST BASED ON THE
TIGHT MODEL SPREAD.//
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