WDPN31 PGTW 111500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN) 
WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 13W, LOCATED APPROXIMATELY 470 NM 
SOUTH OF TOKYO, JAPAN, HAS TRACKED NORTHEASTWARD AT 09 KNOTS OVER 
THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY SHOWS A 
FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH A VERY SMALL 
AREA OF FLARING CONVECTION DISPLACED TO THE NORTHWEST. DESPITE A 
RECENT, SMALL FLARE-UP, THIS CONVECTION HAS BEEN ON A WEAKENING 
TREND DURING THE PAST 12 HOURS. AN 11/0859Z TRMM 85 GHZ MICROWAVE 
SATELLITE IMAGE ALSO SHOWS THIS AREA OF CONVECTION NORTHWEST OF THE 
LLCC WITH DRY, SUBSIDENT AIR NOW WRAPPING AROUND ALL BUT THE 
NORTHEASTERN QUADRANT OF TD 13W. AN 11/0841Z WINDSAT PASS SHOWS 25-
KNOT UNFLAGGED WIND BARBS ALONG THE SOUTHEASTERN PERIPHERY OF THE 
LLCC. CURRENT POSITION IS BASED ON THE AFOREMENTIONED SCATTEROMETRY, 
IR, AND MICROWAVE IMAGERY WITH HIGH CONFIDENCE. INTENSITY IS 
BASED ON DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW, RJTD, AND 
KNES RANGING FROM 25 TO 35 KNOTS. UPPER LEVEL STREAMLINE ANALYSIS 
SHOWS TD 13W IS LOCATED JUST SOUTHWEST OF AN ANTICYCLONE IN A REGION 
OF WEAK TO MODERATE (10-20 KNOTS) EASTERLY VERTICAL WIND SHEAR 
(VWS). ANIMATED WATER VAPOR IMAGERY INDICATES OUTFLOW INTO A 
SOUTHWESTERLY-DRIFTING TROPICAL UPPER TROPOSPHERIC (TUTT) CELL WEST 
OF KYUSHU HAS SLIGHTLY DECREASED DURING THE PAST 12 HOURS. A WEAK 
EQUATORWARD OUTFLOW CHANNEL HAS PERSISTED AND IS AIDING IN THE 
SUSTAINMENT OF CONVECTION. TD 13W IS CURRENTLY TRACKING ALONG THE 
NORTHWEST PERIPHERY OF A LOW TO MID-LEVEL SUBTROPICAL RIDGE (STR) 
AXIS.
3. A. THERE ARE NO CHANGES TO THE FORECAST PHILOSOPHY. 
   B. THIS SYSTEM IS EXPECTED TO CONTINUE TRACKING NORTHEASTWARD AND 
SLOWLY WEAKEN DUE TO INCREASINGLY UNFAVORABLE ENVIRONMENTAL 
CONDITIONS, SUCH AS DECREASING OCEAN HEAT CONTENT AND DRY AIR 
ENTRAINMENT FROM THE WEST. BY TAU 36 THE SYSTEM IS EXPECTED TO 
DISSIPATE OVER WATER. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT 
WITH THE EXCEPTION OF ECMWF, WHICH CURVES TD 13W NORTH AT TAU 24 AND 
NORTHWESTWARD BY TAU 36. THIS CURVE MAY BE DUE TO ECMWF LOSING 
TRACK OF THE LLCC AS TD 13W BEGINS TO DISSIPATE. THIS FORECAST TRACK 
IS SIMILAR TO THE PREVIOUS FORECAST AND IS TO THE RIGHT AND FASTER 
THAN CONSENSUS AFTER TAU 12 TO OFFSET THE UNLIKELY ECMWF SCENARIO.
//
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