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

From: SIU Weather Processor <[email-masked]>
Date: Sat, 13 Nov 2010 07:43:11 -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. THE CURRENT POSITION IS BASED ON A
131130Z PGTW SATELLITE FIX AND A 131110Z 37GHZ SSMIS MICROWAVE
IMAGE. THE CURRENT INTENSITY ESTIMATE OF 25 KNOTS IS BASED ON A
DVORAK ESTIMATE OF 20-25 KNOTS FROM PGTW. 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.
3. FORECAST REASONING:
    A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST REASONING FOR
TD 18W.
    B. TD 18W IS TRACKING SLOWLY WEST-NORTHWESTWARD UNDER THE
INFLUENCE OF THE LOW TO MID-LEVEL SUBTROPICAL RIDGE. DYNAMIC AIDS
ARE IN GOOD AGREEMENT IN SUSTAINING THIS TRACK THROUGH TAU 12, WHEN
TD 18 WILL MAKE LANDFALL OVER CENTRAL VIETNAM AND DISSIPATE OVER
LAND. THE COMPETING INFLUENCES OF VIGOROUS POLEWARD OUTFLOW OVER THE
NORTHEAST SIDE AND INCREASING VERTICAL WINDSHEAR 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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