WDPN31 PGTW 010300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (SAOLA) WARNING NR 17// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 10W (SAOLA), LOCATED APPROXIMATELY 180 NM SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTH-NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS DEEP BANDING CONVECTION CONTINUES TO BUILD AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC) ALONG THE NORTHWESTERN QUADRANT. TRACK SPEEDS HAVE BEEN SLOW BUT STEADY OVER THE PAST 12 HOURS. THE CURRENT INTENSITY OF 85 KNOTS IS BASED ON DVORAK ESTIMATES FROM PGTW, KNES AND RJTD INCREASING OVER THE PAST SIX HOURS. THE MAIN STEERING INFLUENCE APPEARS TO BE THE NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. IT APPEARS THE NER IS SLOWLY BUILDING NORTHWESTWARD PUSHING TY 10W TOWARDS THE DEEP LAYERED SUBTROPICAL RIDGE (STR). TRACK SPEED HAS SLOWED SLIGHTLY OVER THE PAST SIX HOURS IN THIS POORLY DEFINED STEERING ENVIRONMENT. UPPER LEVEL ANALYSIS INDICATES THE EQUATORWARD AND EASTWARD OUTFLOW CHANNELS REMAIN WELL ESTABLISHED, HOWEVER RECENT ANIMATED WATER VAPOR IMAGERY INDICATES POLEWARD OUTFLOW CONTINUES TO EXPAND NORTHWARD AND IS HELPING TO ACCOUNT FOR THE RECENT IMPROVEMENT IN INTENSITY. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING. B. TY 10W IS FORECAST TO SLOWLY DRIFT IN A GENERAL NORTHWESTWARD DIRECTION UNDER THE INFLUENCE OF THE COMPETING STEERING MECHANISMS FOR THE NEXT 24-36 HOURS. AFTER TAU 36 THE STR TO THE NORTH IS EXPECTED TO BECOME THE DOMINANT STEERING INFLUENCE CAUSING THE TRACK TO SHIFT MORE WESTWARD WITH A SUBSEQUENT SPEED INCREASE. UPPER LEVEL CONDITIONS SHOULD GRADUALLY BECOME MORE FAVORABLE AND SEA SURFACE TEMPERATURES SHOULD PEAK NEAR 29C ALLOWING FOR TY 10W TO INTENSIFY TO A PEAK OF 105 KNOTS BY TAU 48. LANDFALL IS EXPECTED SLIGHTLY AFTER TAU 48, WITH FRICTIONAL FORCES STARTING TO WEAKEN TY 10W THROUGH TAU 72. C. BEYOND TAU 72 TY 10W SHOULD RAPIDLY DISSIPATE OVER LAND. NUMERICAL MODEL GUIDANCE HAS BEEN STEADILY IMPROVING OVER THE PAST FEW RUNS AND IS CURRENTLY IN GOOD AGREEMENT WITH THE FORECAST PHILOSOPHY. THE FORECAST IS SLIGHTLY FASTER THAN THE CONSENSUS THROUGH TAU 48 BUT SLOWS MORE QUICKLY ONCE TY 10W MAKES LANDFALL. TRACK FORECAST CONFIDENCE REMAINS LOW DUE TO THE WEAK STEERING ENVIRONMENT AND TIMING OF THE NORTHWESTWARD SHIFT; HOWEVER IT IS IMPROVING.// NNNN