Tropical Storm HAGIBIS Advisory 10月10日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 20W (HAGIBIS) WARNING NR
019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 20W (HAGIBIS), LOCATED APPROXIMATELY 798 NM
SOUTH OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY REVEALS A 20 NAUTICAL MILE (NM) EYE, PROVIDING
GOOD CONFIDENCE FOR THE INITIAL POSTION PLACEMENT. ADDITIONALLY, THE
EYE IS SHOWING TROCHOIDAL MOTION OVER THE PAST 6 HRS. A 091619Z
AMSR2 89GHZ IMAGE DISPLAYS CONCENTRIC EYEWALLS, HOWEVER THE CIMSS M-
PERC PRODUCT IS NOT INDICATING A HIGH LIKELIHOOD OF AN EYEWALL
REPLACEMENT CYCLE (ERC) OCCURRING AT THIS TIME. THE INITIAL
INTENSITY IS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF 7.0 (140
KTS) BY PGTW AND RJTD. FURTHERMORE, THERE IS A 090835Z SMAP IMAGE
(40 KM RESOLUTION) WITH MAX WIND SPEEDS OF 128 KTS (1-MINUTE
AVERAGE) THAT SUPPORTS THE CURRENT INTENSITY ESTIMATE. STY 20W HAS
STRONG RADIAL OUTFLOW; THE POLEWARD OUTFLOW IS BEING FURTHER
ENHANCED BY A TROUGH TO THE NORTHWEST OF THE SYSTEM. FURTHERMORE,
THE SYSTEM IS SITTING IN FAVORABLE ENVIRONMENTAL CONDITIONS WITH
WARM SST (29C) AND LOW VERTICAL WIND SHEAR (VWS). STY 20W IS
CURRENTLY WOBBLING TO THE NORTH-NORTHEAST AFTER A SHIFT FROM A NORTH-
NORTHWESTWARD TRACK OVER THE PAST 6-12 HOURS.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE. WIND RADII HAVE BEEN ADJUSTED
BASED ON RECENT ASCAT-C AND SMAP DATA--THIS DATA CONTINUES TO
INDICATE AN EXPANSIVE GALE WIND FIELD.
   B. STY 20W WILL TRACK NORTH-NORTHWESTWARD ALONG THE WESTERN
PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) THROUGH TAU 36
WITH LOW VWS, WARM SST, AND STRONG UPPER-LEVEL OUTFLOW. STY 20W IS
EXPECTED TO MAINTAIN INTENSITY FOR THE FIRST 12 HOURS DUE TO THE
ENHANCED POLEWARD OUTFLOW. HOWEVER, STY 20W IS EXPECTED TO BEGIN A
GRADUAL WEAKENING TREND AFTER TAU 12 AS THE TROUGH BEGINS TO
INTERFERE WITH OUTFLOW. NUMERICAL MODELS REMAIN IN GOOD CROSS-TRACK
AGREEMENT BUT POOR ALONG-TRACK SPEED AGREEMENT. AFTER TAU 36, A
SHORTWAVE TROUGH WILL PASS OVER JAPAN, WEAKENING THE STR AND
ALLOWING STY 20W TO BEGIN RECURVING. STY 20W WILL BEGIN EXTRA-
TROPICAL TRANSITION (ETT) NEAR TAU 48. OVERALL, THERE IS GOOD
CONFIDENCE IN THE OFFICIAL JTWC FORECAST IN THIS PORTION OF THE
TRACK.
   C. AFTER TAU 72, VWS WILL INCREASE SIGNIFICANTLY, SSTS WILL DROP
BELOW 24 DEGREES CELSIUS, FRICTIONAL EFFECTS FROM SKIRTING HONSHU
WILL DISRUPT THE STRUCTURE, AND A LOW LEVEL NORTHEASTERLY COLD SURGE
WILL BUILD IN TO THE WEST, ALL COMBINING TO CAUSE MORE RAPID
WEAKENING. STY 20W WILL ACCELERATE NORTHEASTWARD AND COMPLETE ETT BY
TAU 84 AS THE SYSTEM BECOMES EMBEDDED IN THE MIDLATITUDE WESTERLIES
AND GAINS STRONG FRONTAL CHARACTERISTICS. NUMERICAL MODELS ARE IN
FAIR CROSS-TRACK AGREEMENT AFTER RECURVATURE OF STY 20W. HOWEVER, AS
THE SYSTEM ACCELERATES, ALONG-TRACK SPREAD GREATLY INCREASES THROUGH
TAU 96. THE JTWC FORECAST TRACK IS PLACED NEAR BUT SLIGHTLY FASTER
THAN THE MULTI-MODEL CONSENSUS AFTER TAU 72. BASED ON THE VARIATION
IN MODEL TIMING OF THE RECURVE AND ALONG-TRACK SPEEDS, THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.//
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