WDPN31 PGTW 161500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (MA-ON)// WARNING NR 21// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TYPHOON (TY) 08W (MA-ON), LOCATED APPROXIMATELY 850 NM SOUTH OF TOKYO, JAPAN, HAS TRACKED NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS THAT MA-ON HAS BEGUN TO TURN POLEWARD IN THE INITIAL STAGE OF WHAT WILL BE A TWO- DAY CHURN AROUND THE SUBTROPICAL RIDGE. WITH THE LATEST FIX, THE 24 HOUR NET MOVEMENT OF THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS NOW VEERED TO 290. THE SUBTROPICAL RIDGE, WHICH HAS BEEN STEADY AND STATIONARY TO THE SOUTHEAST OF TOKYO FOR SEVERAL DAYS, HAS BEEN GUIDING TY 08W STEADILY ALONG ITS SOUTHERN PERIPHERY. THE LATEST SOUNDING FROM NAZE (NORTHERN RYUKUS) SHOWS LIGHT SOUTHEASTERLIES ALOFT, WHILE THOSE FROM FUKUOKA AND KAGOSHIMA (KYUSHU) SHOW SOUTHERLIES AND 500 MB HEIGHTS NEAR 5900 METERS. COMBINED, THESE INDICATE THAT THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE IS NOW OVER KYUSHU. THE RIDGE IS BEGINNING TO WEAKEN AND TILT FROM NORTHWEST THROUGH SOUTHEAST. ANIMATED WATER VAPOR IMAGERY IS SHOWING THE BEGINNING OF THIS PROCESS, WHERE A SUBTROPICAL JET STREAMING OUT OF THE HIMALAYAS CAN BE SEEN MERGING WITH A WEAK FINGER OF THE SOUTHERN BRANCH OF THE POLAR FRONT JET OVER THE GULF OF BOHAI. ANIMATED WATER VAPOR IMAGERY ALSO REVEALS MUCH IMPROVED POLEWARD OUTFLOW OVER THE NORTHEASTERN QUADRANT AS A FRAGMENTED TROPICAL UPPER TROPOSPHERIC TROUGH FILLS, BUT SUPPRESSION CONTINUES OVER THE NORTHWEST QUADRANT. THE EYEWALL IS CONTINUOUS AROUND THE LLCC BUT REMAINS THIN OVER THE NORTHERN SEMICIRCLE. ALTHOUGH A 160708Z SSMI 37GHZ IMAGES SHOWS THICK, WELL-ORGANIZED BANDING AROUND THE LLCC, A 160837Z SSMIS 91 GHZ IMAGE REVEALS A LACK OF DEEP CONVECTION THROUGHOUT THE NORTHWESTERN SEMICIRCLE. EQUATORWARD OUTFLOW REMAINS VIGOROUS, AND VERTICAL WIND SHEAR HAS EASED TO APPROXIMATELY 10 KNOTS. THE CURRENT INTENSITY ANALYSIS OF 110 KNOTS IS BASED ON AN AVERAGE OF DVORAK ESTIMATES OF 102 KNOTS FROM PGTW AND 115 FROM KNES. 3. FORECAST REASONING A. THERE IS NO SIGNIFICANT CHANGE IN FORECAST PHILOSOPHY. B. TY 08W WILL CONTINUE ITS TRACK AROUND THE RIDGE DURING THE NEXT 48 HOURS. TY 08W WILL REMAIN IN VERY FAVORABLE ENVIRONMENTAL CONDITIONS THROUGH THE FIRST 72 HOURS AND SHOULD CONTINUE TO INTENSIFY. ALONG-TRACK SEA SURFACE TEMPERATURES RUN FROM 29 THROUGH 31 DEGREES AND VERTICAL WIND SHEAR WILL REMAIN BELOW 15 KNOTS. PEAK INTENSITY WILL OCCUR NEAR TAU 36, JUST BEFORE MA-ON CRESTS THE RIDGE AXIS. THE RIDGE AXIS WILL EXTEND ALONG THE 29TH LATITUDE. GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 48, THEN BEGINS TO DIVERGE AFTER THE STORM CRESTS THE RIDGE AXIS. ALL AIDS CROSS 30 DEGREES NORTH LATITUDE BETWEEN 132 AND 134 DEGREES EAST, HOWEVER. THE JTWC FORECAST STAYS CLOSE TO CONSENSUS THROUGH TAU 48. AFTER TAU 48, THE JTWC TRACK MOVES EAST OF CONSENSUS, WHICH IS BEING PULLED WESTWARD BY THE BAROTROPIC MODEL AND LATER NORTHEAST TURNS BY JGSM AND ECMWF. C. TYPHOON 08W WILL ROUND THE RIDGE AND TRACK SEAWARD OF THE KANTO PLAIN BETWEEN TAU 96 AND 108. SEA SURFACE TEMPERATURES ALONG TRACK ARE WARM ALL THE WAY THROUGH COASTAL JAPAN, AND VERTICAL WIND SHEAR WILL NOT INCREASE SUBSTANTIALLY UNTIL NEAR TAU 96. THEREFORE, LAND INTERACTION WITH THE RUGGED TERRAIN OF SHIKOKU AND THEN HONSHU WILL BE THE PRIMARY WEAKENING MECHANISM, ALLOWING TY 08W TO REMAIN AT GREATER THAN TYPHOON STRENGTH AS IT PASSES THE KANTO PLAIN. GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON TRACK, WITH THE EASTERNMOST MODELS BOUNCING THE STORM OFF EXTREME SOUTHWESTERN SHIKOKU BEFORE TURNING IT HARD TO THE RIGHT, AND THE WESTERNMOST MODELS JUST MISSING THE WAKAYAMA PENINSULA. ALL GUIDANCE HAS ALIGNED WITH A PASSAGE SEAWARD OF THE KANTO. VERTICAL WIND SHEAR WILL INCREASE TO NEAR 20 KNOTS AFTER TAU 96, PUTTING TY 09W ON A DOWNWARD INTENSITY TREND AS IT PASSES THE KANTO.// NNNN