Tropical Storm CHAN-HOM Advisory 10月10日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING
NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 343 NM
SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 07
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY DEPICTS A FULLY-EXPOSED LOW LEVEL
CIRCULATION CENTER WITH ASSOCIATED CONVECTION SHEARED TO THE
NORTHEAST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON THE FULLY-EXPOSED NATURE OF THE LLCC AND LOW LEVEL FEATURES
EVIDENT IN A 091629Z AMSR2 89 GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY IS SET AT 50 KTS AND IS SUPPORTED BY MULTI-AGENCY DVORAK
INTENSITY ESTIMATES RANGING FROM T2.5-3.5 (35-55 KTS) AND A 091740Z
ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.8 (43 KTS). A 091627Z AMSR2
WINDSPEED PRODUCT REVEALS SWATHS OF 50 KT WINDS AROUND THE LLCC,
LENDING GOOD CONFIDENCE TO THE INITIAL INTENSITY. UPPER LEVEL
ANALYSIS REVEALS A ROBUST POLEWARD OUTFLOW CHANNEL ASSOCIATED WITH
THE JET POSITIONED OVER JAPAN BEING OFFSET BY HIGH (>30 KT) VERTICAL
WIND SHEAR (VWS) VALUES. SEA SURFACE TEMPERATURES (SST) REMAIN
CONDUCIVE AT 26-27 CELSIUS. OVERALL, TS 16W IS TRACKING THROUGH AN
UNFAVORABLE ENVIRONMENT FOR DEVELOPMENT ALONG THE NORTHERN PERIPHERY
OF A SUBTROPICAL RIDGE. THE SYSTEM IS TRACKING ALONG THE EDGE OF THE
BAROCLINIC ZONE AND HAS BEGUN SUBTROPICAL TRANSITION (STT) AS IT
BEGINS TO EXHIBIT A COMBINATION OF TROPICAL AND EXTRATROPICAL
CHARACTERISTICS.
3. FORECAST REASONING.
   A. THE FORECAST PHILOSOPHY HAS SHIFTED FROM AN EXTRATROPICAL
TRANSITION TO A DISSIPATION SCENARIO IN THIS PROGNOSTIC REASONING
BASED ON MODEL GUIDANCE.
   B. TS 16W WILL CONTINUE TO TRACK EAST-NORTHEASTWARD THEN EASTWARD
THROUGH TAU 24 AS IT CONTINUES STT, INTERACTING WITH THE BAROCLINIC
ZONE TO THE NORTH. PERSISTENTLY HIGH VWS WILL LEAD TO STEADY
WEAKENING TO 40 KTS BY TAU 24. AFTER THIS, THE SYSTEM WILL TURN TO A
SOUTHEASTWARD TRACK AS A BREAK APPEARS WITHIN THE STR. ALONG THIS
TRACK, THE SYSTEM WILL RAPIDLY WEAKEN DUE TO HIGH VWS VALUES AND DRY
AIR ENTRAINMENT. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 24. AFTERWARDS, ALL MODEL SOLUTIONS BEGIN TO TURN THE
SYSTEM TO THE SOUTHEAST WITH SPREAD INCREASING TO 202 NM BY TAU 48.
THIS DIVERGENCE IN TRACK GUIDANCE PLACES OVERALL POOR CONFIDENCE IN
THE JTWC FORECAST TRACK, WHICH IS PLACED NEAR THE MULTI-MODEL
CONSENSUS AND THE ECMWF TRACK SOLUTION.//
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