Tropical Storm BOLAVEN Advisory Fri Aug 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W (BOLAVEN) WARNING NR 17//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 16W (BOLAVEN), LOCATED APPROXIMATELY 445 NM SOUTHEAST OF
KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWESTWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
AND A 232354Z SSMIS 37 GHZ MICROWAVE IMAGE SHOW SEVERAL FORMATIVE
FEEDER BANDS WRAPPING INTO THE LOW-LEVEL CIRCULATION CENTER (LLCC).
THE NOTICEABLE LACK OF DEEP CONVECTION OVER THE NORTHWESTERN
QUADRANT SIX HOURS AGO HAS SINCE BEGUN TO BUILD IN AS RADIAL OUTFLOW
IMPROVES AND VERTICAL WIND SHEAR SLIGHTLY EASED TO 10-15 KNOTS FROM
THE NORTH. THE CURRENT POSITION IS BASED ON THE AFOREMENTIONED
IMAGERY AND AGREEABLE CENTER FIXES FROM PGTW AND RJTD WITH HIGH
CONFIDENCE. THE CURRENT INTENSITY IS BASED ON THE HIGHER SIDE OF
DVORAK ESTIMATES RANGING FROM 77 TO 102 KNOTS FROM KNES, RJTD, AND
PGTW. UPPER-LEVEL ANALYSIS INDICATES TY 16W IS LOCATED APPROXIMATELY
TEN DEGREES EQUATORWARD OF THE NORTHEAST-SOUTHWEST ORIENTATED
SUBTROPICAL RIDGE (STR) AXIS. THE SELF-MAINTAINED MESO-ANTICYCLONE
REMAINS OVERHEAD OF THE LLCC PROVIDING IMPROVED RADIAL OUTFLOW AND
WEAK (05-10 KNOTS) VWS ABOVE THE SYSTEM. TY 16W CONTINUES TO TRACK
ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP LAYERED STR TO THE
NORTH, ANCHORED JUST EAST OF HONSHU, JAPAN. THE PAST SIX HOUR TRACK
MOTION HAS TAKEN A MORE NORTH-NORTHWESTWARD PATH THEN PREVIOUSLY
EXPECTED AS IT SEEMS THE LARGE SIZE OF TY 16W IS MODIFYING THE
STEERING STR AT A FASTER PACE THEN PREVIOUSLY FORECAST. HOWEVER,
THIS IS A SLIGHT ADJUSTMENT IN FORECAST TRACK AND DOES NOT CHANGE
THE LLCC POSITION WHEN NEAR OKINAWA.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 16W WILL CONTINUE TO TRACK ALONG THE SOUTHWESTERN PERIMETER
OF THE STR THROUGH TAU 72; HOWEVER, GIVEN THE EXTRAORDINARY SIZE AND
MAGNITUDE OF THE CYCLONE, IT WILL CONTINUE TO MODIFY THE STR,
RESULTING IN A MORE POLEWARD STORM MOTION. AFTER TAU 48 A MID-
LATITUDE TROUGH APPROACHING FROM MONGOLIA AND TRACKING TOWARD THE
YELLOW SEA WILL WEAKEN THE STR RESULTING IN AN EVEN MORE POLEWARD
STORM MOTION. THE SYSTEM WILL STEADILY INTENSIFY, PEAKING AT 120
KNOTS BY TAU 36. THE SYSTEM WILL THEN MAINTAIN INTENSITY AS IT
APPROACHES LANDFALL OVER OKINAWA NEAR 260800Z. BY TAU 72 TY 16W
SHOULD BEGIN TO SLOWLY WEAKEN DUE TO DECREASING OCEAN HEAT CONTENT.
HOWEVER, A BRIEF PERIOD OF ENHANCED POLEWARD OUTFLOW OUT AHEAD OF
THE APPROACHING TROUGH SHOULD SLIGHTLY COMBAT THE DECLINING OCEAN
PARAMETERS. OBJECTIVE AID GUIDANCE IS IN TIGHT AGREEMENT WITH ECMWF
REMAINING DIRECTLY OVER OKINAWA. THE MODEL CONSENSUS WAS PULLED
SLIGHTLY EAST OF OKINAWA THIS RUN DUE TO THE RIGHT OUTLIER IN GFDN.
THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE TRACK FORECAST.
   C. AFTER TAU 72, TY 16W SHOULD TRACK NORTHWARD INTO THE WEAKNESS
CAUSED BY THE PREVIOUSLY MENTIONED TROUGH. TRACK SPEEDS WILL
ACCELERATE DURING THIS TIME AND INTENSITY WILL BE ON THE DECLINE AS
OCEAN PARAMETERS BECOME LESS FAVORABLE AND WESTERLY VWS INCREASES TO
STRONG LEVELS. EXTRA-TROPICAL TRANSITION IS EXPECTED TO BEGIN
OVERLAND BY TAU 120. OBJECTIVE AID GUIDANCE IS IN FAIR AGREEMENT IN
REGARDS TO THE LANDFALL POSITION WITH AN APPROXIMATELY 125 NM SPREAD
BETWEEN THE LEFTMOST OUTLIER, GFS, AND THE RIGHTMOST OUTLIER, GFDN.
REGARDLESS, ALL TRACKERS STILL INDICATE LANDFALL OVER THE
NORTHWESTERN PORTION OF THE KOREAN PENINSULA.  DUE TO THE DEEP UPPER-
LEVEL TROUGHING AND AMPLIFIED RIDGING IN RESPONSE THERE IS HIGH
CONFIDENCE IN THIS PORTION OF THE TRACK FORECAST CURVING OVER
NORTHERN KOREA. THIS IS FURTHER VALIDATED BY ANALYSIS OF THE LATEST
GFS AND ECMWF ENSEMBLE RUNS.//
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