Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Depression 18w Warning Nr 04//

From: SIU Weather Processor <[email-masked]>
Date: Sat, 13 Nov 2010 07:59:12 -0600

WDPN31 PGTW 131500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TROPICAL DEPRESSION (TD) 18W, LOCATED APPROXIMATELY 210NM
SOUTHEAST OF HUE CITY, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT 05
KNOTS DURING THE PAST SIX HOURS. BOTH ANIMATED INFRARED
IMAGERY AND MICROWAVE IMAGERY INDICATE CONVECTION IS WANING AND
BECOMING MORE DISORGANIZED. THE LOW LEVEL CIRCULATION CENTER
EXISTS UNDER 20-25 KNOTS OF VERTICAL WINDSHEAR (VWS) AND IS MOVING
INTO AN AREA OF INCREASING VWS. ANIMATED WATER VAPOR IMAGERY
INDICATES A VIGOROUS POLEWARD OUTFLOW CHANNEL REMAINS ON THE
NORTHEAST SIDE OF THE SYSTEM, WHILE SUBSIDENCE AHEAD OF AN
ENCROACHING SHORTWAVE IS SUPPRESSING OUTFLOW OVER THE NORTHWEST
QUADRANT. THE CURRENT POSITION IS BASED ON A 131130Z PGTW SATELLITE
FIX AND A 131110Z 37GHZ SSMIS MICROWAVE IMAGE. THE CURRENT INTENSITY
OF 25 KNOTS IS BASED ON A DVORAK ESTIMATE OF 25 KNOTS FROM PGTW.
3. FORECAST REASONING:
    A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST REASONING.
    B. TD 18W IS TRACKING SLOWLY WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE LOW TO MID-LEVEL SUBTROPICAL RIDGE.
DYNAMIC AIDS ARE IN GOOD AGREEMENT IN SUSTAINING THIS TRACK THROUGH
TAU 12, WHEN TD 18W WILL MAKE LANDFALL OVER CENTRAL VIETNAM. THE
COMPETING INFLUENCES OF VIGOROUS POLEWARD OUTFLOW OVER THE NORTHEAST
SIDE AND INCREASING VWS ARE EXPECTED TO BALANCE OVER THE SHORT TERM,
KEEPING THE SYSTEM AT ITS CURRENT INTENSITY THROUGH LANDFALL. AFTER
TAU 12, THE CYCLONE WILL MOVE INLAND AND DISSIPATE.//

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