Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Depression 10w/

From: SIU Weather Processor <[email-masked]>
Date: Thu, 2 Sep 2010 09:12:37 -0500

WDPN33 PGTW 021500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 10W/
WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION 10W (TEN), LOCATED APPROXIMATELY 545 NM
SOUTHEAST OF OKINAWA, JAPAN, HAS TRACKED NORTHWESTWARD AT 15 KTS OVER
THE PAST SIX HOURS. ANIMATED INFRARED IMAGERY SHOWS THE SYSTEM HAS
OVERALL MAINTAINED ITS CONVECTIVE STRUCTURE WITH ONLY A SLIGHT
IMPROVEMENT IN BANDING. THE CURRENT POSITION IS EXTRAPOLATED FROM A
020930Z SSMIS MICROWAVE SATELLITE IMAGE WITH POOR CONFIDENCE. THE
CURRENT INTENSITY IS BASED ON DVORAK ESTIMATES OF 30 KNOTS FROM PGTW
AND KNES AND FROM DROPSONDE DATA.
3. FORECAST REASONING.
   A. THE EXTENDED PORTION OF THE FORECAST IS NOW MORE TO THE LEFT OF
THE TRACK FORECAST AT 020000Z IN RESPONSE TO A MORE ROBUST STEERING
RIDGE. THE INITIAL HALF OF THE FORECAST IS FUNDAMENTALLY THE SAME.
   B. TD 10W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP
SUBTROPICAL RIDGE ENTRENCHED JUST SOUTH OF MAINLAND JAPAN AND IT
SHOULD CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU 72. THE AVAILABLE
NUMERIC GUIDANCE IS IN OVERALL GOOD AGREEMENT UP TO TAU 36, AFTER
WHICH GFDN AND GFS DIVERGE SHARPLY TO THE LEFT OF THE MODEL ENVELOPE.
THIS TRACK FORECAST IS INITIALLY ON PAR WITH THEM TO THE RIGHT OF
CONSENSUS AFTER TAU 36 TO COMPENSATE FOR THE UNLIKELY DEFLECTION TO
THE LEFT. TD 10W WILL SEE A MEAGER, ALBEIT GRADUAL INTENSIFICATION AS
FAVORABLE ENVIRONMENTAL CONDITIONS PERSIST UP TO TAU 72.
   C. AFTER TAU 72, TD 10W IS EXPECTED TO RECURVE POLEWARD AHEAD OF A
MID-LATITUDE TROUGH FORECAST TO DEEPEN OVER THE YELLOW SEA. POLEWARD
OUTFLOW SHOULD INITIALLY IMPROVE AS THE SYSTEM APPROACHES THE WESTERN
EDGE OF THE SUBTROPICAL RIDGE WITH A PEAK INTENSITY OF 75 KNOTS. THE
FAVORABLE OUTFLOW WILL, HOWEVER, DIMINISH AS WESTERLY VERTICAL WIND
SHEAR PERPENDICULAR TO STORM MOTION INCREASES. BY TAU 120, TD 10W
WILL BEGIN TO WEAKEN AND COMMENCE EXTRATROPICAL TRANSITION.//

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