Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Depression 19w

From: SIU Weather Processor <[email-masked]>
Date: Sun, 12 Dec 2010 07:38:12 -0600

WDPN31 PGTW 121500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W
/WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 19W, LOCATED APPROXIMATELY 325 NM
EAST OF HO CHI MINH, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT
07 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE
IMAGERY INDICATES THAT TD 19W HAS CONSOLIDATED OVER THE PAST 06
HOURS WITH IMPROVED CONVECTIVE BANDING OVER THE SOUTHERN SEMI-
CIRCLE WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION CENTER.
THE IMPROVED ORGANIZATION IS CLEARLY EVIDENT IN A 120913Z SSMI
IMAGE, WHICH SHOWS DEEP CONVECTIVE BANDING NORTHWEST WRAPPING
INTO THE SOUTHEAST QUADRANT AND WELL-DEFINED LOW-LEVEL BANDING
IN ALL OTHER QUADRANTS. TD 19W IS LOCATED SOUTH OF THE UPPER-
LEVEL RIDGE AXIS AND IS UNDER LIGHT TO MODERATE, EASTERLY
VERTICAL WIND SHEAR. SUBSEQUENTLY, OUTFLOW IS PREDOMINANTLY
POLEWARD AND IS CONFINED TO THE WESTERN SEMI-CIRCLE. THERE
IS FAIR CONFIDENCE IN THE CURRENT POSITION BASED ON THE
120913Z SSMI IMAGE. THE CURRENT INTENSITY OF 25 KNOTS IS
BASED ON DVORAK ESTIMATES OF T1.5 (25 KNOTS) FROM BOTH PGTW
AND KNES.
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING BULLETIN.
   B. TD 19W IS TRACKING WEST-NORTHWESTWARD UNDER THE STEERING
INFLUENCE OF THE LOW-LEVEL (700 MB) SUBTROPICAL RIDGE (STR)
POSITIONED NORTH OF THE SYSTEM. THE 12/00Z 700MB ANALYSIS SHOWS
THE STR EXTENDING ACROSS THE NORTHERN SOUTH CHINA SEA INTO
NORTHERN VIETNAM. AVAILABLE MODEL GUIDANCE (TO INCLUDE NOGAPS,
ECMWF, GFS, JGSM AND UKMO) IS CONSISTENT IN MAINTAINING THE
STR THROUGH THE FORECAST PERIOD, THEREFORE, TD 19W IS FORECAST
TO CONTINUE TRACKING WESTWARD. THE SYSTEM SHOULD MAKE LANDFALL
OVER VIETNAM NEAR TAU 36 AND IS EXPECTED TO DISSIPATE BY TAU
48.//

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