Subject: Pacific-NW: Subj/prognostic Reasoning For Typhoon 12w Warning Nr 16//

From: SIU Weather Processor <[email-masked]>
Date: Sat, 18 Sep 2010 09:17:12 -0500

WDPN31 PGTW 181500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 12W (FANAPI), LOCATED APPROXIMATELY 165 NM EAST-
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED WEST-NORTHWESTWARD AT 09
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE
IMAGERY AND A 181122Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICT A 16 NM
EYE WITH MULTIPLE DEEP CONVECTIVE BANDS ALONG THE SOUTHERN PERIPHERY
OF THE SYSTEM. A RADAR LOOP FROM MIYAKOJIMA, JAPAN AND ENHANCED IR
IMAGERY INDICATE TY 12W IS CURRENTLY UNDERGOING AN EYE-WALL
REPLACEMENT CYCLE. THERE IS HIGH CONFIDENCE IN THE CURRENT POSITION
BASED ON AN EYE FIX IN IR AND A MICROWAVE EYE IN THE AFOREMENTIONED
SSMIS IMAGE. THE CURRENT INTENSITY IS SLIGHTLY HIGHER THEN DVORAK
ESTIMATES FROM PGTW, RJTD, AND KNES WHICH RANGE FROM 90 TO 102 KNOTS
BASED ON SATELLITE INTENSITY ESTIMATES OF 115 KNOTS AND THE OVERALL
STRUCTURE OF THE SYSTEM IN IR AND MICROWAVE IMAGERY. THERE IS FAIR
CONFIDENCE IN THE WIND RADII STRUCTURE BASED ON OBSERVATIONS FROM
ISHIGAKIJIMA, JAPAN (30 NM NORTH-NORTHWEST OF THE SYSTEM) INDICATING
60 KNOT WINDS FROM THE NORTHEAST AS WELL AS OBSERVATIONS FROM
MIYAKOJIMA, JAPAN (75 NM NORTHEAST OF THE SYSTEM) INDICATING 35 KNOT
WINDS GUSTING TO 53 KNOTS OUT OF THE EAST-SOUTHEAST. ANIMATED WATER
VAPOR IMAGERY CONTINUES TO SHOW ENHANCED EQUATORWARD OUTFLOW,
HOWEVER POLEWARD OUTFLOW IS SOMEWHAT HINDERED BY AN ANTICYCLONE
NORTH OF THE SYSTEM CAUSING INCREASED NORTHEASTERLY VERTICAL WIND
SHEAR. TY 12W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF
A SUBTROPICAL STEERING RIDGE ANCHORED OVER NORTHEASTERN CHINA.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE OVERALL FORECAST PHILOSOPHY FROM THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 12W IS FORECAST TO CONTINUE TRACKING WESTWARD ALONG THE
SOUTHERN PERIPHERY OF THE SUBTROPICAL STEERING RIDGE THROUGHOUT THE
FORECAST PERIOD. THE SYSTEM IS FORECAST TO INTENSIFY SLIGHTLY
FOLLOWING THE COMPLETION OF AN EYE-WALL REPLACEMENT CYCLE, BEFORE
MAKING LANDFALL OVER CENTRAL TAIWAN BETWEEN TAU 12 AND TAU 24. BY
TAU 36 THE SYSTEM IS EXPECTED TO MAKE LANDFALL AGAIN OVER EASTERN
CHINA AND DISSIPATE RAPIDLY AS IT CONTINUES TO TRACK INLAND.
NUMERICAL MODEL GUIDANCE REMAINS TIGHTLY PACKED THROUGHOUT THE
FORECAST PERIOD; THEREFORE THIS FORECAST IS CLOSE TO MODEL
CONSENSUS.//

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