Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Depression 16w Warning Nr 09//

From: SIU Weather Processor <[email-masked]>
Date: Sat, 23 Oct 2010 09:17:12 -0500

WDPN32 PGTW 231500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 16W (SIXTEEN), LOCATED APPROXIMATELY
640 NM SOUTH-SOUTHEAST OF OKINAWA, JAPAN, HAS TRACKED WEST-NORTHWEST-
WARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED WATER VAPOR
SATELLITE IMAGERY SHOWS THE SYSTEM HAS STRUGGLED TO MAINTAIN DEEP
CONVECTION DUE TO MODERATE VERTICAL WIND SHEAR (VWS) AND SUBSIDENT
FLOW FROM THE NORTH INDUCED BY A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT). THE INITIAL POSITION IS BASED ON ANIMATED SATELLITE IMAGERY
AND ON A 231105Z SSMI-S MICROWAVE PASS WITH POOR CONFIDENCE.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE IN FORECAST PHILOSOPHY SINCE
THE PREVIOUS BULLETIN.
   B. TD 16W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF
A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTH AND IS
EXPECTED TO TRACK MORE POLEWARD BY TAU 36 AS IT BEGINS TO ROUND THE
STR TOWARDS RECURVATURE IN RESPONSE TO AN APPROACHING MID-LATITUDE
TROUGH. AS THE TUTT MENTIONED IN PARA 2.A. MOVES WESTWARD, THE  VWS
AND SUBSIDENCE WILL DECREASE, ALLOWING THE SYSTEM TO STEADILY INTENSIFY.
  C. BEYOND TAU 72, TD 16W WILL CONTINUE TO TRACK POLEWARD ALONG THE
WESTERN PERIPHERY OF THE STEERING RIDGE. THE SYSTEM WILL FURTHER
INTENSIFY AS POLEWARD OUTFLOW INITIALLY IMPROVES WITH THE SYSTEM'S
EXPOSURE TO THE UPPER LEVEL WESTERLIES. THE AVAILABLE NUMERIC
GUIDANCE IS SPLIT WITH NOGAPS, GFS, UKMO, AND ECMWF FAVORING A
POLEWARD TURN WHILE GFDN AND JGSM ARE TRACKING THE SYSTEM STRAIGHT
TOWARDS THE WEST ALONG A PRESUMABLY STRONGER STR. THIS FORECAST IS IN
AGREEMENT WITH THE MODELS TRACKING MORE POLEWARD IN ANTICIPATION OF
THE MID-LATITUDE TROUGH THAT IS CURRENTLY MOVING ACROSS SOUTHEAST
CHINA.//

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