Subject: Pacific-NW: Subj/prognostic Reasoning For Typhoon 16w Warning Nr 27//

From: SIU Weather Processor <[email-masked]>
Date: Wed, 27 Oct 2010 21:38:06 -0500

WDPN32 PGTW 280300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W WARNING NR 27//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 16W (CHABA), LOCATED APPROXIMATELY 140 NM SOUTH-
SOUTHEAST OF KADENA AIR BASE, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD
AT 09 KNOTS OVER THE PAST SIX HOURS. DESPITE COMPLETING AN EYEWALL
REPLACEMENT CYCLE, TY CHABA HAS MANAGED TO INTENSIFY SLIGHTLY WITHIN
THE LAST 12 HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS AN
ENLARGED, SYMMETRIC 40 NM EYE. INITIAL POSITION WAS BASED ON THE
PGTW FIX AND KADENA RADAR FIX. PGTW, KNES, AND RJTD DVORAK ESTIMATES
ARE INDICATING INTENSITIES BETWEEN 102 TO 127 KNOTS. THE SYSTEM HAS
INTENSIFIED DUE TO DUAL OUTFLOW CHANNELS, WITH AN ENHANCED POLEWARD
OUTFLOW CHANNEL INTO AN UPPER LEVEL, MID-LATITUDE TROUGH TO THE
NORTHEAST. TY 16W IS CURRENTLY TRACKING ALONG THE NORTHWESTERN
PERIPHERY OF A MID-LEVEL SUBTROPICAL STEERING RIDGE TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 16W IS EXPECTED TO CONTINUE TRACKING ALONG THE NORTHWESTERN
PERIPHERY OF THE SUBTROPICAL STEERING RIDGE AND CONTINUE TO ROUND
THE RIDGE AXIS. WITHIN THE NEXT 12 HOURS THE SYSTEM SHOULD START
WEAKENING WITH INCREASING VERTICAL WIND SHEAR, ASSOCIATED WITH A MID-
LATITUDE UPPER LEVEL TROUGH TO THE NORTHWEST, AND DECREASING OCEAN
HEAT CONTENT. AROUND TAU 24, TY CHABA SHOULD START TO ACCELERATE
NORTHEASTWARD AND BEGIN TO INTERACT WITH THE STRONG MID-LATITUDE
WESTERLIES. BY TAU 48, TY 16W SHOULD BECOME ABSORBED BY THE
BAROCLINIC ZONE AND FULLY TRANSITION INTO AN EXTRATROPICAL LOW,
WHCIH IS EVIDENT IN THE 500MB HEIGHT MODEL FIELDS.
   C. AFTER TAU 48, TY 16W WILL CONTINUE TO TRACK NORTHEASTWARD AS
AN EXTRATROPICAL LOW. MODEL GUIDANCE IS IN GOOD AGREEMENT, HOWEVER
THIS FORECAST IS JUST SOUTH AND AHEAD OF MODEL CONSENSUS TO ACCOUNT
FOR THE TENDENCY OF THE CONSENSUS TO BE SLOW IN A RECURVATURE
SCENARIO.//

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