WDPN31 PGTW 130300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 08W (MA-ON), LOCATED APPROXIMATELY 700 NM 
EAST-SOUTHEAST OF IWO TO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 
09 KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED MULTISPECTRAL 
IMAGERY SHOWS THE DEEP CONVECTION BEGINNING TO FORM A CONCENTRIC 
RING AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). ANALYSIS OF THE 
NOAA-BD REVERSE ANIMATION SHOWS SOME FRAGMENTATION OF THE CONCENTRIC 
DEEP CONVECTION ON THE NORTHWESTERN AND SOUTHEASTERN QUADRANTS OF 
THE STORM ALONG WITH A TREND OF WARMING CLOUD TOPS WITHIN THE ENTIRE 
RING OF CONVECTION. A 122302Z AMSU 89GHZ IMAGE SHOWS THE DEEP 
CONVECTION ASSOCIATED WITH THE NEWLY FORMED RING AND FRAGMENTED 
FEEDER BANDS TO THE SOUTHEAST. A 12/2314Z ASCAT PASS SHOWS THE GALE 
FORCE WINDS WRAPPING AROUND THE NORTHWESTERN PERIPHERY OF THE LLCC. 
WATER VAPOR ANIMATION SHOWS THAT THE TROPICAL UPPER TROPOSPHERIC 
TROUGH (TUTT) CELL LOCATED TO THE NORTHWEST OF TS 08W HAS CONTINUED 
TO MOVE WESTWARD, THEREBY HAVING LESS OF AN IMPACT ON THE STORM. 
ADDITIONALLY, AS TS 08W CONTINUES TO COALESCE AND INTENSIFY, IT IS 
STARTING TO DEVELOP ITS OWN FAVORABLE ENVIRONMENT DUE TO INCREASING 
UPPER LEVEL DIVERGENCE. TS 08W CONTINUES TO PROPAGATE AWAY FROM
THE QUASISTATIONARY TUTT CELL POSITIONED FURTHER TO THE EAST NEAR THE
DATELINE, HOWEVER, THE WATER VAPOR LOOP SHOWS THAT THE TROUGHING 
ASSOCIATED WITH THE TUTT IS DEEPENING AND DIGGING EQUATORWARD WHICH 
IS HELPING TO ENHANCE THE EASTWARD OUTFLOW. THERE IS INCREASED 
CONFIDENCE IN THE CURRENT POSITION BASED ON A 122212Z TRMM 37GHZ 
IMAGE AND THE WELL-DEFINED LLCC IN VISIBLE IMAGERY. THE CURRENT 
INTENSITY IS BASED ON (BUT ASSESSED SLIGHTLY LOWER THAN) DVORAK 
ESTIMATES OF 55 KNOTS FROM PGTW, KNES AND RJTD.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN FORECAST PHILOSOPHY. 
   B. THE ANTICYCLONE SOUTHEAST OF TOKYO IS EXPECTED TO REMAIN 
STEADY AND STATIONARY THROUGH 72 HOURS, WHICH WILL KEEP TS 08W ON A 
WEST-NORTHWESTWARD COURSE ALONG THE SOUTHERN FLANK OF THE MID-LEVEL
SUB-TROPICAL RIDGE. VERTICAL WIND SHEAR ALONG TRACK WILL REMAIN 
BELOW 15 KNOTS AND SEA SURFACE TEMPERATURES WILL REMAIN HIGH 
(BETWEEN 30 AND 32 DEGREES). MODEL GUIDANCE IS IN GOOD AGREEMENT 
THROUGH TAU 72. THE INTENSITY FORECAST FOLLOWS STIPS GUIDANCE 
CLOSELY. 
   C. DURING THE EXTENDED FORECAST PERIOD, TS 08W WILL MODIFY THE 
MID-LEVEL STEERING RIDGE DUE TO THE LARGE SIZE OF THE STORM AND THE 
ASSOCIATED UPPER LEVEL DIVERGENCE AND OUTFLOW. THIS WILL ALLOW FOR 
THE FORECAST TRACK TO BEGIN A POLEWARD TURN. THE TRACK FORECAST 
REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND IS SUPPORTED BY 
THE MODEL CONSENSUS AND THE ECMWF MODEL. THE REMAINING MODELS HAVE 
SHIFTED ABRUPTLY WITH NOGAPS, GFDN AND GFS NOW INDICATING A SHARPER, 
MORE POLEWARD RECURVATURE. THE UKMET MODEL IS THE SOLE MODEL 
INDICATING A FAST WESTWARD TRACK THROUGH THE FORECAST PERIOD.//
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