Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Depression 14w Warning Nr 03//

From: SIU Weather Processor <[email-masked]>
Date: Tue, 5 Oct 2010 09:21:05 -0500

WDPN31 PGTW 051500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 14W WARNING NR 03//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 14W, LOCATED APPROXIMATELY 240 NM
NORTH-NORTHEAST OF HUE, VIETNAM, HAS TRACKED NORTHWARD AT 05 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS
A WEAKENING, POORLY-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH DEEP CONVECTION SHEARED OVER THE EASTERN SEMI-CIRCLE OF THE
PARTIALLY-EXPOSED LLCC. FORTUNATELY, A 051100Z SSMIS 91 GHZ IMAGE
AND CMA ANIMATED RADAR IMAGERY SHOW THE WEAKLY-DEFINED CENTER WITH
FAIR CONFIDENCE AND ALSO PROVIDE FURTHER EVIDENCE THAT THE SYSTEM
HAS RAPIDLY WEAKENED OVER THE PAST 12 HOURS. THE CURRENT INTENSITY
IS BASED ON PERSISTENCE, PRIMARILY FROM THE 050255Z ASCAT IMAGE
SHOWING NUMEROUS 30 KNOT WIND VECTORS OVER THE NORTHWEST QUADRANT.
DUE TO THE RAPIDLY DECAYING DEEP CONVECTION, DVORAK ESTIMATES ARE
UNCLASSIFIABLE.
3. FORECAST REASONING.
   A. OVER THE PAST 12 HOURS THE FORECAST PHILOSOPHY HAS CHANGED
SIGNIFICANTLY, REFLECTING MUCH SLOWER TRACK SPEEDS AND A MORE
EASTWARD TRACK. ADDITIONALLY, THE PEAK INTENSITY HAS BEEN REDUCED
TO 30 KNOTS.
   B. TD 14W IS SITUATED WITHIN A WEAK STEERING ENVIRONMENT AND
WITHIN A HOSTILE ENVIRONMENT CHARACTERIZED BY MODERATE (25 KNOTS)
VERTICAL WIND SHEAR (VWS) AND LAND INTERACTION. THE 05/00Z 700 MB
ANALYSIS DEPICTS A WEAK RIDGE POSITIONED EAST OF THE SYSTEM WITH A
COL REGION NORTH ASSOCIATED WITH A MIDLATITUDE SHORTWAVE TROUGH
SITUATED OVER EASTERN ASIA. THIS TROUGH IS FORECAST TO PROVIDE A
SHORT-TERM EASTWARD INFLUENCE THROUGH TAU 12-24. HOWEVER, AFTER THE
TROUGH PROPAGATES EAST, THE RIDGE WILL BUILD NORTH OF THE SYSTEM
PRODUCING QUASI-STATIONARY MOTION. ADDITIONALLY, STRONG UPPER-LEVEL
WESTERLIES NORTH OF 20N IN COMBINATION WITH LOW-LEVEL NORTHEASTERLY
FLOW, ASSOCIATED WITH A 1021 MB HIGH OVER CHINA, HAVE PRODUCED
INCREASING VWS VALUES IN EXCESS OF 30 KNOTS JUST NORTH AND NORTHEAST
OF THE SYSTEM. OVERALL, TD 14W APPEARS TO BE BOXED IN AN UNFAVORABLE
ENVIRONMENT; ANY SUSTAINED MOTION NORTH OR NORTHEAST WILL RESULT IN
INCREASING VWS AND FURTHER WEAKENING, THEREFORE, IT IS LIKELY THAT
THE SYSTEM WILL CONTINUE TO WEAKEN AND DE-COUPLE OVER THE NEXT 1-2
DAYS AT THE LATEST WITH DISSIPATION EXPECTED BETWEEN TAU 36 AND 48.
EARLIER DISSIPATION IS POSSIBLE AS WELL AS QUASI-STATIONARY MOTION.
MODEL GUIDANCE SUPPORTS THE FORECAST REASONING. THIS FORECAST IS
CONSISTENT WITH THE MODEL CONSENSUS.//

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe from WX-TROPL send e-mail to [email-masked] with
"unsub wx-tropl" in the body of your message. For help with WX-TROPL
write to [email-masked]. For more information on tropical weather products, see the NHC Homepage at http://www.nhc.noaa.gov.