WDPN31 PGTW 170300
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 170000Z8 TO 200000Z2 OCT 02.
    A. TROPICAL DEPRESSION (TD) 27W, LOCATED APPROXIMATELY 660 NM 
EAST-NORTHEAST OF SAIPAN, HAS TRACKED WESTWARD AT 9 KNOTS OVER THE 
PAST SIX HOURS. THE WARNING POSITION IS BASED ON 162330Z5 VISIBLE 
AND ENHANCED INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS 
BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 25 TO 30 KNOTS. 
SATELLITE ANIMATION AND A 161904Z1 QUIKSCAT PASS DEPICTS A SMALL, 
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH 
CONVECTION SHEARED TO THE NORTH.
    B. TD 27W IS UNDER THE STEERING INFLUENCE OF A MID-LEVEL 
SUBTROPICAL RIDGE TO THE NORTHEAST OF THE LLCC. TD 27W IS EXPECTED 
TO REMAIN SOUTH OF THE RIDGE AXIS THROUGH THE 24-HOUR FORECAST 
PERIOD, THEN TRACK INCREASINGLY NORTHWESTWARD FOR THE REMAINDER OF 
THE PERIOD, TRACKING TOWARDS A WEAKNESS IN THE RIDGE. THE AVAILABLE 
MODELS CONSISTING OF NOGAPS, UKMET GLOBAL (EGRR), AND THE JAPANESE 
GLOBAL (JGSM) ARE HAVING DIFFICULTY INITIALIZING ON THIS SMALL 
SYSTEM. HOWEVER, ALL MODEL GUIDANCE DOES SUGGEST A WEST-
NORTHWESTWARD TRACK. OUR FORECAST IS BASED ON NGPS, CSUM, CLIPPER, 
AND A BLEND OF THE BETA ADVECTION MODELS.
    C. TD 27W IS EXPECTED TO INTENSIFY AT A SLIGHTLY LESS THAN 
CLIMATOLOGICAL RATE THROUGH THE FORECAST PERIOD AS IT TRACKS IN A 
MARGINAL UPPER LEVEL ENVIRONMENT AND APPROACHES THE RIDGE AXIS.
    D. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR A SMALL-
SIZED SYSTEM.
3. FORECAST TEAM: MAZANY/AYALA/HEATH/CUTMAN/ANDERSON//

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