Subject: Pacific-NW: Subj/prognostic Reasoning For Typhoon 12w Warning Nr 18//

From: SIU Weather Processor <[email-masked]>
Date: Sat, 18 Sep 2010 21:26:16 -0500

WDPN31 PGTW 190300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W WARNING NR 18//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 12W (FANAPI), LOCATED APPROXIMATELY 80 NM SOUTH OF
TAIPEI, TAIWAN, HAS TRACKED WESTWARD AT 14 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A CLOUD-FILLED
EYE AS TY 12W MAKES LANDFALL OVER TAIWAN. THERE IS HIGH CONFIDENCE
IN THE INITIAL POSITION, WHICH IS BASED ON AN EYE FIX AND A TAIWAN
RADAR FIX. THE INITIAL INTENSITY IS BASED ON PGTW, KNES, AND RJTD
DVORAK ESTIMATES RANGING FROM 90 TO 115 KNOTS. ADDITIONALLY,
OBSERVATIONS FROM HUALIEN, TAIWAN ARE INDICATING MEAN SURFACE LEVEL
WINDS OF 45KTS WITH GUSTS OF 115 KNOTS, APPROXIMATELY 20NM TO THE
NORTH-NORTHWEST. ANIMATED WATER VAPOR IMAGERY CONTINUES TO SHOW
EXCELLENT 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 WEAKEN AS IT CONTINUES TO
TRACK OVER TAIWAN. BY TAU 24, TY 12W 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 IN
AGREEMENT WITH MODEL CONSENSUS.//

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