Subject: Pacific-NW: Subj/prognostic Reasoning For Typhoon 16w Warning Nr 29//

From: SIU Weather Processor <[email-masked]>
Date: Thu, 28 Oct 2010 08:43:09 -0500

WDPN32 PGTW 281500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W WARNING NR 29//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 16W (CHABA), LOCATED APPROXIMATELY 130 NM EAST-
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT
12 KNOTS OVER THE PAST SIX HOURS. ANIMATED WATER VAPOR SATELLITE
IMAGERY SHOWS THE SYSTEM REMAINED SYMMETRIC AS THE TIGHTLY-WRAPPED
DEEP CONVECTIVE BANDS AROUND THE LOW LEVEL CIRCULATION CENTER
CONSTRICTED. THE 10 NM EYE HAS BECOME CLOUD-FILLED OVER THE PAST
THREE HOURS INDICATING AN INITIAL WEAKENING TREND. THE CURRENT
POSITION WAS BASED ON THE 281130Z PGTW EYE FIX AND SUPPORTED BY
KADENA RADAR FIXES. THE CURRENT INTENSITY IS AVERAGED FROM PGTW,
KNES, AND RJTD DVORAK ESTIMATES RANGING FROM 102 TO 115 KNOTS. RADIAL
OUTFLOW APPEARS TO BE DIMINISHING AS THE SYSTEM TRACKS 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 CHABA IS EXPECTED TO CONTINUE TRACKING NORTHEASTWARD,
COMMENCE EXTRATROPICAL TRANSITION (ET) BY TAU 36 AND COMPLETE ET BY
TAU 48. THE SYSTEM WILL START WEAKENING WITH INCREASING VERTICAL
WIND SHEAR ASSOCIATED WITH A MIDLATITUDE UPPER LEVEL TROUGH TO THE
NORTHWEST, AND DECREASING OCEAN HEAT CONTENT. AFTER TAU 24, TY 16W
WILL START TO ACCELERATE NORTHEASTWARD AND BEGIN TO INTERACT WITH
THE STRONG MID-LATITUDE WESTERLIES. MODEL GUIDANCE IS IN GOOD
AGREEMENT, EXCEPT GFDN ACTING AS THE SOLE OUTLIER TO THE LEFT OF THE
MODEL ENVELOPE. THIS FORECAST IS JUST TO THE RIGHT AND AHEAD OF
MODEL CONSENSUS TO OFFSET GFDN'S UNLIKELY PULL TO THE LEFT AND TO
ACCOUNT FOR THE TENDENCY OF THE CONSENSUS TO BE SLOW IN A RECURVATURE
SCENARIO.//

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