Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Storm 11w Warning Nr 05//

From: SIU Weather Processor <[email-masked]>
Date: Wed, 8 Sep 2010 21:48:09 -0500

WDPN31 PGTW 090300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W WARNING NR 05//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 11W (ELEVEN), LOCATED APPROXIMATELY 250 NM
SOUTH-SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTHEASTWARD AT 06
KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) INDICATES A WELL DEFINED LOW LEVEL
CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION FLARING OVER THE
CENTER AND BEING SHEARED EAST-NORTHEAST OF THE SYSTEM. DIRECT
CYCLONE INTERACTION (DCI) WITH A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) CELL, WHICH HAS REFLECTED DOWN TO THE SURFACE, HAS CAUSED TS
11W TO SLOW AND MAKE AN ABRUPT NORTHEASTWARD TURN FROM WHAT WAS
PREVIOUSLY FORECAST. THERE IS FAIR CONFIDENCE IN THE CURRENT
POSITION AND PAST SIX HOUR MOTION BASED ON MSI, THE TAIWAN RADAR
LOOP, AND A 082332Z AMSU 89 GHZ MICROWAVE IMAGE. THE CURRENT
INTENSITY IS BASED ON DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD.
3. FORECAST REASONING.
   A. THE CURRENT FORECAST PHILOSOPHY HAS SHIFTED FROM A
NORTHWESTWARD TRACK ALONG A LOW TO MID-LEVEL SUBTROPICAL STEERING
RIDGE TO A POLEWARD TRACK BASED ON RECENT MSI DEPICTING BINARY
INTERACTION WITH A SURFACE REFLECTION OF THE TUTT CELL NORTHWEST OF
THE SYSTEM.
   B. TS 11W IS CURRENTLY TRACKING NORTHEASTWARD DUE TO DCI WITH THE
AFOREMENTIONED TUTT CELL. BY TAU 12, TS 11W IS EXPECTED TO TURN
POLEWARD, THEN SLIGHTLY NORTHWESTWARD, NEAR TAU 24, AS THE TUTT CELL
MOVES FURTHER OVER EASTERN CHINA AND INDUCES A SLIGHT CYCLONIC
ROTATION. TS 11W IS FORECAST TO MAKE LANDFALL BY TAU 36. AFTER TAU
36, THE SYSTEM IS EXPECTED TO TURN BACK POLEWARD AS IT BEGINS TO
INTERACT WITH AN APPROACHING MID-LATITUDE TROUGH, AND RAPIDLY
DISSIPATE DUE TO INTERACTION WITH MOUNTAINOUS TERRAIN ALONG THE
COAST OF EASTERN CHINA. NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF GFDN WHICH IS AN OUTLIER AND TRACKS
THE SYSTEM ERRONEOUSLY WESTWARD. THIS FORECAST IS SLIGHTLY EAST OF
CONSENSUS TO ACCOUNT FOR THIS GFDN, AND IS WITHIN THE TIGHT MODEL
PACKING OF WBAR, NGPS, JGSM, ECMWF, AND GFS.//

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