Tropical Storm HAISHEN Advisory Fri Sep 04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 11W (HAISHEN) WARNING NR
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 11W (HAISHEN), LOCATED APPROXIMATELY 493
NM SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. STY 11W HAS RAPIDLY INTENSIFIED
50 KNOTS OVER THE PAST 24 HOURS FROM 85 KNOTS TO THE CURRENT
INTENSITY OF 135 KNOTS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS A 35NM ROUND EYE, WHICH SUPPORTS THE INITIAL POSITION WITH
GOOD CONFIDENCE. A 032200Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTS A
COMPACT EYEWALL, APPROXIMATELY 100NM DIAMETER, WITH SPIRAL BANDING
OVER THE SOUTHERN SEMICIRCLE. THE INITIAL INTENSITY IS ASSESSED AT
135 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM
6.5 (127 KNOTS) TO 7.0 (140 KNOTS). UPPER-LEVEL ANALYSIS REVEALS A
FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR (VWS) AND RADIAL
OUTFLOW. ADDITIONALLY, SST VALUES (30-31C) AND HIGH OCEAN HEAT
CONTENT VALUES ARE CONDUCIVE FOR FURTHER DEVELOPMENT. THE 03/1200Z
500MB ANALYSIS SHOWS A DEEP MIDLATITUDE SHORTWAVE TROUGH OVER THE
EAST CHINA SEA AND WESTERN JAPAN WITH A BROAD SUBTROPICAL RIDGE
ENTRENCHED NORTH OF THE SYSTEM AND A WEAK EXTENSION OF THIS STR
EXTENDING SOUTHWESTWARD TO ABOUT 25N 130E. STY 11W IS TRACKING WEST-
NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE DEEP-LAYERED
SUBTROPICAL RIDGE (STR) AND IS TRACKING TOWARD A COL REGION
POSITIONED JUST SOUTH OF OKINAWA.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. THE STR IS FORECAST TO BUILD AND REMAIN STATIONARY OVER JAPAN
WITH THE SHORTWAVE TROUGH GRADUALLY FILLING OVER THE KOREAN
PENINSULA. THE NUMERICAL MODEL TRACKERS ARE NOW IN CLOSER AGREEMENT
NEAR OKINAWA WITH A SPREAD OF 70NM. THE FORECAST TRACK REMAINS
HIGHLY CONSISTENT WITH THE PREVIOUS FORECAST AND INDICATES A NORTH-
NORTHWESTWARD TRACK OVER AMAMI OSHIMA THEN JUST WEST OF KYUSHU AT
TAU 72. NUMERICAL MODEL GUIDANCE HAS REMAINED STABLE AND THE 03/12Z
ECMWF ENSEMBLE ALSO SUPPORTS THE FORECAST TRACK, HOWEVER, THE SYSTEM
COULD TRACK CLOSER TO SASEBO / KYUSHU DUE TO UNCERTAINTY IN THE
MODELS, WHICH ARE IN OVERALL FAIR AGREEMENT WITH A 100NM SPREAD IN
SOLUTIONS NEAR TAU 72. STY 11W IS FORECAST TO MAINTAIN STY INTENSITY
THROUGH TAU 36 WITH GRADUAL WEAKENING AFTER TAU 36 AS THE SYSTEM
TRACKS POLEWARD.
   C. IN THE EXTENDED PERIOD, NUMERICAL MODEL GUIDANCE DIVERGES WITH
INCREASING UNCERTAINTY IN THE EXACT TRACK OVER SOUTH KOREA. STY 11W
IS FORECAST TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 72 AS
IT INTERACTS WITH THE SHORTWAVE TROUGH AND WILL ACCELERATE POLEWARD
AND COMPLETE ETT BY TAU 96 WHEN IT GAINS FRONTAL CHARACTERISTICS
OVER NORTH KOREA. SIGNIFICANT WEAKENING WILL OCCUR OVER THE KOREAN
PENINSULA DUE TO INCREASING VWS AND INTERACTION WITH MOUNTAINOUS
TERRAIN. OVERALL, THERE IS MODERATE CONFIDENCE IN THE JTWC FORECAST
TRACK, WHICH IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS.//
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