Tropical Storm CHAN-HOM Advisory 10月11日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING
NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 187 NM
SOUTH OF YOKOSUKA, JAPAN, HAS TRACKED EASTWARD AT 13 KNOTS (KTS)
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A BROAD, PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH A WEAK FRONTAL STRUCTURE AND DEEP CONVECTION
SHEARED TO THE EAST. OVERALL, THERE IS GOOD CONFIDENCE IN THE
INITIAL POSITION AND RECENT TRACK MOTION. A 101643Z ATMS 88.2 GHZ
MICROWAVE IMAGE INDICATES DEEPER CONVECTION DISPLACED TO THE
NORTHEAST AND WEAK SHALLOW BANDING WRAPPING INTO A LLCC. BASED ON
PGTW AND RJTD DVORAK CURRENT INTENSITY ESTIMATES OF T3.0 (45 KTS),
THE INITIAL INTENSITY REMAINS ASSESSED AT 50 KTS, SUPPORTED BY
RECENT ASCAT DATA REVEALING 45-50 KT WINDS TO THE NORTH OF THE LLCC.
ENVIRONMENTAL ANALYSIS SHOWS MARGINAL CONDITIONS AND IS
CHARACTERIZED BY STRONG VERTICAL WIND SHEAR (VWS) AND INCREASING DRY
AIR ENTRAINMENT. ADDITIONALLY, TS 16W IS EXPERIENCING BAROCLINIC
INFLUENCES AS THE SYSTEM IS EMBEDDED WITHIN THE ZONAL SUBTROPICAL
WESTERLY FLOW AND TRACKING ALONG THE SOUTHERN PERIPHERY OF THE
BAROCLINIC ZONE. ADDITIONALLY, THERE ARE BROAD LOW-LEVEL SUBTROPICAL
RIDGES (STR) ENTRENCHED TO THE EAST AND SOUTHWEST OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. DUE TO THE PRESENCE OF THE AFOREMENTIONED LOW-LEVEL
SUBTROPICAL RIDGES, TS 16W IS EXPECTED TO DECELERATE AND TURN
SOUTHEASTWARD THEN SOUTHWARD THROUGH THE FORECAST PERIOD. THE SYSTEM
WILL STEER ALONG THE EASTERN PERIPHERY OF THE LOW-LEVEL STR LOCATED
TO THE SOUTHWEST. ALTHOUGH THE EASTERN STR IS FORECAST TO WEAKEN, IT
WILL CONTINUE TO BLOCK THE EASTWARD PROGRESSION OF THE SYSTEM. DUE
TO INCREASING (25-35 KT) VWS AND CONTINUED DRY AIR ENTRAINMENT, TS
16W SHOULD WEAKEN THROUGHOUT THE FORECAST PERIOD WITH DISSIPATION
EXPECTED BY TAU 48. NUMERICAL MODEL GUIDANCE DIVERGES AS THE SYSTEM
TURNS SOUTHWARD, BUT LENDS OVERALL SUPPORT THE JTWC FORECAST TRACK
WITH FAIR CONFIDENCE.//
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