WDPN31 PGTW 241500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION (TD) 17W/
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 241200Z9 TO 271200Z2 SEP 2003.
   A. TROPICAL DEPRESSION (TD) 17W, LOCATED APPROXIMATELY 480 NM
WEST-NORTHWEST OF GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 10 KNOTS
OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED ON 241130Z1
ENHANCED INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 25 KNOTS. THE LOCATION
OF THE LOW LEVEL CIRCULATION CENTER FOR TD 17W IS STILL HIGHLY
UNCERTAIN AS IT IS EMBEDDED IN A BROAD TROUGH. ANIMATED ENHANCED
INFRARED WATER VAPOR IMAGERY SHOWS THAT THE OUTFLOW IS BEING
ENHANCED BY A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE
NORTHEAST OF TD 17W.
   B. TD 17W IS EXPECTED TO CONTINUE TO TRACK NORTHWESTWARD
ALONG THE SOUTHERN PERIPHERY OF A LOW TO MID LEVEL STEERING RIDGE
ANCHORED TO THE EAST OF JAPAN. A MAJOR SHORTWAVE TROUGH IN EASTERN
CHINA IS EXPECTED TO ADVANCE AND WEAKEN THE RIDGE AXIS CREATING
A WEAKNESS IN THE SUBTROPICAL RIDGE NEAR KYUSHU, JAPAN. TD 17W
WILL TRACK TOWARDS THIS WEAKNESS AND TRANSITION TO A MORE POLEWARD
TRACK IN APPROXIMATELY 24 HOURS. THE AVAILABLE DYNAMIC AIDS OF
NOGAPS, UKMET EGRR, WBAI, AND NCEP GFS ARE IN FAIR AGREEMENT WITH
THIS FORECAST SCENARIO. NOGAPS IS A SIGNIFICANT EASTERN OUTLIER
TO THIS FORECAST SCENARIO BECAUSE IT FORECASTS THE STEERING RIDGE
TO BE MUCH WEAKER THAN OTHER MODELS RESULTING IN AN IMMEDIATE
POLEWARD TRACK. THIS FORECAST IS BASED ON A CONSENSUS OF THE
AVAILABLE DYNAMIC AIDS WITH LESS EMPHASIS ON NOGAPS.
   C. TD 17W IS EXPECTED TO EXPERIENCE WEAK VERTICAL SHEAR AND OUTFLOW
ENHANCED IN THE SHORT TERM BY THE NEARBY TUTT CELL ALLOWING TD 17W TO
INTENSIFY AT A CLIMATOLOGICAL RATE FOR THE ENTIRE FORECAST PERIOD.
   D. CURRENT WIND RADII AND FORECAST WIND RADII ARE BASED
ON CLIMATOLOGY FOR AN AVERAGE SIZED SYSTEM.
3. FORECAST TEAM: GRUBER/HEATH/BAK/PACILIO/ANDERSON//

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