Tropical Storm HAISHEN Advisory 9月5日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 11W (HAISHEN) WARNING NR
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 11W (HAISHEN), LOCATED APPROXIMATELY 329 NM
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWESTWARD AT
09 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A WELL-DEFINED
22-NM ROUND EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE EYE FEATURE, ADJUSTED FOR A VERY SLIGHT SOUTHWESTWARD
TILT. THE INITIAL INTENSITY OF 135 KTS IS BASED ON THE HIGH END OF
MULTI-AGENCY DVORAK ESTIMATES RANGING FROM T6.5 (127 KTS) TO T7.0 (140
KTS) AND REFLECTS THE SUSTAINED HIGHLY SYMMETRIC AND COMPACT EIR
STRUCTURE. STY 11W IS IN AN OVERALL FAVORABLE ENVIRONMENT WITH LOW
(05-10KT) NORTHEASTERLY VERTICAL WIND SHEAR (VWS), EXCELLENT RADIAL
OUTFLOW, AND WARM (30-31C) SEA SURFACE TEMPERATURES (SST). THE CYCLONE
IS TRACKING UNDER THE STEERING INFLUENCE OF THE DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST, SITTING EAST OF HOKKAIDO
JAPAN.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. STY 11W WILL CONTINUE ON ITS CURRENT TRACK UNDER THE STEERING
STR. AROUND TAU 24, A SHORTWAVE TROUGH APPROACHING FROM THE NORTHWEST
WILL WEAKEN THE STR AND ALLOW THE SYSTEM TO TRACK MORE POLEWARD, PASS
JUST TO THE WEST OF KYUSHU, JAPAN, ACROSS THE KOREA STRAIT, MAKE
LANDFALL JUST WEST OF BUSAN, SOUTH KOREA BEFORE TAU 60, THEN DRAG
NORTHWARD ALONG THE RUGGED MOUNTAIN RANGES OF THE KOREAN PENINSULA.
INCREASING VWS, COOLING SSTS, AND EVENTUALLY, LAND INTERACTION WILL
GRADUALLY, THEN RAPIDLY ERODE THE SYSTEM, AND BY TAU 72 WILL BE
REDUCED TO 45 KTS AFTER IT CROSSES INTO NORTH KOREA. CONCURRENTLY, THE
CYCLONE WILL BEGIN EXTRA-TROPICAL TRANSITION AROUND TAU 48 AS IT
ENTERS THE BAROCLINIC ZONE AND TRANSFORM INTO A STORM-FORCE COLD CORE
LOW BY TAU 72.
   C. BEYOND TAU 72, STY HAISHEN WILL CONTINUE NORTHWARD AND CROSS
INTO MANCHURIA AND BY TAU 96, REDUCED TO A WEAK 25-KT EXTRA-TROPICAL
LOW. NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH ECMWF AND JGSM
OUTLYING ON THE RIGHT OF THE MODEL ENVELOPE AFTER TAU 36. THERE IS
OVERALL HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID JUST
LEFT OF THE MULTI-MODEL CONSENSUS BEYOND TAU 36 TO OFFSET THE
OUTLIERS.//
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