Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Depression 14w Warning Nr 01//

From: SIU Weather Processor <[email-masked]>
Date: Mon, 4 Oct 2010 23:24:08 -0500

WDPN31 PGTW 050300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 14W WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 14W (FOURTEEN), LOCATED
APPROXIMATELY 40 NM SOUTH OF HAINAN, HAS TRACKED NORTHWARD
AT 06 KNOTS DURING THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE
IMAGERY INDICATES THAT CONVECTION HAS CONSOLIDATED AND INCREASED
DRAMATICALLY DURING THE PAST SIX HOURS. A 041857Z AMSU-B MICROWAVE
IMAGE SHOWS A COMMA-SHAPED CONVECTIVE BAND FEEDING INTO THE LOW
LEVEL CIRCULATION CENTER (LLCC). AN EARLIER ASCAT IMAGE CONFIRMS A
LARGE CYCLONIC WIND FIELD WITH NEAR GALE FORCE WINDS WITHIN THE
NORTHEASTERN QUADRANT. A VIGOROUS POLEWARD OUTFLOW CHANNEL HAS
DEVELOPED AND IS BEING ENHANCED BY AN UPPER LEVEL ANTICYCLONE JUST
SOUTH OF HAINAN ISLAND. THIS CHANNEL IS AIDING DEEP CONVECTION NEAR
THE SYSTEM CENTER. DESPITE THE COMMA PATTERN INDICATED ON A 042346Z
91 GHZ SSMIS IMAGE, CONFIDENCE IN THE EXACT POSITION OF THE LLCC IS
ONLY FAIR AS THE CIRCULATION IS EMBEDDED WITHIN THE MONSOON TROUGH.
INTENSITY ESTIMATES ARE BASED ON A COMBINATION OF SURFACE AND SHIP
OBSERVATIONS AND A PGTW DVORAK ESTIMATE OF 2.0.
 3. FORECAST REASONING.
   A. THIS MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY FOR TD 14W.
   B. TD 14W IS FORECAST TO DRIFT NORTHWARD OVER HAINAN ISLAND AND
WEAKEN, THEN RE-INTENSIFY AS IT TRACKS INTO THE EASTERN GULF OF
TONKIN AT TAU 24. SUSTAINED FAVORABLE OUTFLOW CONDITIONS COUPLED
WITH WARM SEA SUFACE TEMPERATURES ARE EXPECTED TO MITIGATE THE
EFFECTS OF LAND INTERACTION AND ENABLE THE SYSTEM TO INTENSIFY TO
LOW TROPICAL STORM STRENGTH BEFORE IT MAKES LANDFALL OVER SOUTHERN
CHINA. WEAK STEERING FLOW IN THE MID-LEVELS INDICATE THAT THE SYSTEM
WILL LIKELY DRIFT NORTHWARD TOWARDS THE WEAKEST PART OF THE
SUBTROPICAL RIDGE, INTENSIFY TO THE EXTENT THAT IT REMAINS OVER
WATER, AND THEN DISIPATE OVER LAND. DUE TO A LACK OF AVAILABILITY OF
MANY OF THE MOST RELIABLE DYNAMIC AIDS AND EXTREMELY POOR
AGREEMENT OF THOSE AVAILABLE, THE SHORT-TERM FORECAST IS BASED ON A
CONSTANT RATE OF MOVEMENT. THE LONG TERM FORECAST IS BASED ON THE
1200Z ECMWF MODEL RUN.//

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