Tropical Storm NEOGURI Advisory Mo, 21.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (NEOGURI) WARNING
NR 019//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 21W (NEOGURI), LOCATED APPROXIMATELY 521 NM
SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 19
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTI-SPECTRAL SATELLITE
IMAGERY SHOWS THE SYSTEM IS BEING SIGNIFICANTLY SHEARED NORTHEASTWARD
AS IT HAS MOVED UNDER AN AREA OF VERY STRONG (45-50 KTS) UPPER-LEVEL
SOUTHWESTERLY FLOW INDUCED BY A DEEP TROUGH TO THE WEST. THE SYSTEM
HAS ALREADY BEGUN TRANSITIONING INTO AN EXTRA-TROPICAL COLD-CORE LOW
AS IT HAS BEGUN INTERACTING WITH THE BAROCLINIC ZONE. THE INITIAL
POSITION IS PLACED WITH FAIR CONFIDENCE DUE TO THE BROADENING NATURE
OF THE LOW-LEVEL CIRCULATION, ASSOCIATED WITH THE EXTRA-TROPICAL
TRANSITION (ETT). THE INITIAL INTENSITY OF 55 KTS IS BASED ON AN
AVERAGE OF AGENCY DVORAK ESTIMATES RANGING FROM 3.0 (45 KTS) TO 4.0
(65 KTS). AS PREVIOUSLY MENTIONED THE SYSTEM IS EXPERIENCING VERY
STRONG (45-50KT) VERTICAL WIND SHEAR (VWS), ALBEIT PARTIALLY OFFSET
BY ROBUST POLEWARD OUTFLOW. TS 21W IS TRACKING NORTHEAST AROUND THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 21W IS FORECAST TO CONTINUE TRACKING QUICKLY TO THE
NORTHEAST REMAINING OFF THE SOUTHEAST COAST OF JAPAN AND BY TAU 36 TS
21W WILL TRACK PAST TOKYO AND BE SOUTH OF NORTHERN HONSHU. VWS IS
EXPECTED TO INCREASE EVEN MORE (> 65KTS) AND BY TAU 24, THE SYSTEM
WILL COMPLETE ETT AND TRANSFORM INTO A COLD-CORE LOW WITH AN
EXPANDING, STRONG GALE-FORCE WIND FIELD EMBEDDED IN THE BAROCLINIC
ZONE. CONSEQUENTLY, THE LOW LEVEL CIRCULATION CENTER WILL CONTINUE TO
BE DIFFICULT TO PINPOINT THROUGHOUT THE ETT. MODEL GUIDANCE HAS
REMAINED WIDELY ERRATIC WITH SEVERAL MODELS HAVING ISSUES TRACKING
THE VORTEX AS IT TRACKS INSIDE THE BAROCLINIC ZONE. OVERALL, THERE IS
LOW CONFIDENCE IN THE JTWC FORECAST TRACK.//
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