Tropical Storm CHABA Advisory 02 Οκτ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 21W (CHABA) WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 21W (CHABA), LOCATED APPROXIMATELY 551 NM SOUTH-
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWESTWARD AT
12 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS THE SYSTEM HAS SIGNIFICANTLY CONSOLIDATED AND
BECOME MORE SYMMETRICAL, ALBEIT THE CONVECTIVE SIGNATURE HAS
VIRTUALLY NOT CHANGED IN THE PAST SIX HOURS. THE INITIAL POSITION IS
BASED ON A CENTRAL WARM PIXEL IN THE EIR LOOP AND EXTRAPOLATED FROM
CURRENT STORM MOTION WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS
MAINTAINED AT 65 KNOTS BASED ON CONGRUENT AGENCY DVORAK ESTIMATES.
TY 21W IS TRACKING IN A FAVORABLE ENVIRONMENT WITH STRONG DIFFLUENCE
ALOFT, LOW (5-10 KNOT) VERTICAL WIND SHEAR (VWS), AND VERY WARM (30C)
SEA SURFACE TEMPERATURES (SSTS). TY 21W IS TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TY 21W WILL CONTINUE NORTHWESTWARD OVER THE NEXT 36 HOURS
TOWARDS OKINAWA. AFTERWARDS, IT WILL ROUND THE STR AXIS AND RECURVE
TO THE NORTHEAST. ENVIRONMENTAL CONDITIONS WILL REMAIN FAVORABLE FOR
CONTINUED INTENSIFICATION, PEAKING AT 110 KNOTS BY TAU 48 PARTLY DUE
TO AN APPROACHING MID-LATITUDE TROUGH THAT WILL ENHANCE POLEWARD
OUTFLOW. BY TAU 72, THE CYCLONE WILL APPROACH KYUSHU, JAPAN, AND
BEGIN TO WEAKEN MOSTLY DUE TO INCREASING VWS AND COOLING SSTS.
DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH THIS PORTION
OF THE FORECAST PROVIDING HIGH CONFIDENCE.
   C. IN THE EXTENDED FORECAST, TY CHABA WILL MAKE LANDFALL OVER
KYUSHU, JAPAN AND ACCELERATE NORTHEASTWARD. THE SYSTEM WILL DRAG
ACROSS THE JAPANESE ISLAND CHAIN AND RAPIDLY ERODE DUE TO LAND
INTERACTION, IN ADDITION TO STRONG (30-40 KNOT) VWS. CONCURRENTLY,
THE SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AND IS EXPECTED
TO COMPLETE ETT BY THE END OF THE FORECAST PERIOD AFTER IT TRACKS
BACK INTO THE PACIFIC OCEAN EAST OF MISAWA. DYNAMIC MODEL GUIDANCE
CONTINUES TO SPREAD BOTH IN TERMS OF SPEED AND DIRECTION AFTER TAU
72. IN VIEW OF THIS, THERE REMAINS LOW CONFIDENCE IN THE EXTENDED
PORTION OF THE JTWC TRACK FORECAST.//
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