WDPN31 PGTW 171500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (MA-ON)// WARNING NR 25// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TYPHOON (TY) 08W (MA-ON), LOCATED APPROXIMATELY 700 NM SOUTH- SOUTHWEST OF TOKYO, JAPAN, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS THAT MA-ON IS COMING OUT OF ITS EYEWALL REPLACEMENT CYCLE (ERC) AND BEGINNING TO RE-ORGANIZE. A 170826Z SSMIS IMAGE SHOWS THE OLD EYEWALL HAS NEARLY DISAPPEARED AND DEEP CONVECTION IS COMMENCING IN THE NEW EYE WALL. THE ERC PROCESS HAS TAKEN A LOT OUT OF THE STORM, MAKING FOR A FLAT INTENSITY TREND OVER THE PAST 24 HOURS. RECENT ANIMATED INFRARED IMAGERY SHOWS PRONOUNCED WARMING OF THE CLOUD TOPS AROUND THE EYE AND AGENCY DVORAK ESTIMATES FROM ALL AGENCIES ARE FALLING. THE CURRENT INTENSITY ANALYSIS IS BASED ON A DVORAK ESTIMATES RANGING FROM 90 TO 105 KNOTS FROM PGTW, RJTD, AND KNES. TY 08W IS CURRENTLY IN A HIGHLY FAVORABLE ENVIRONMENT FOR RE- INTENSIFICATION. VERTICAL WIND SHEAR IS BELOW 10 KNOTS AND SEA SURFACE TEMPERATURES ARE 29 TO 30 DEGREES. ANIMATED WATER VAPOR IMAGERY SHOWS SUBSTANTIAL IMPROVEMENT IN POLEWARD OUTFLOW, AND EQUATORWARD OUTFLOW REMAINS VIGOROUS. TROUGHING OVER THE RYUKUS IS STILL PRODUCING SOME IMPINGEMENT ON OUTFLOW OVER THE WESTERN QUADRANT, BUT THAT IS ALSO EASING. THE SUBTROPICAL RIDGE CONTINUES TO WEAKEN AND SHIFT SOUTHEAST, GIVING TY 08W AN ALLEY TO APPROACH SOUTHERN JAPAN. SOUNDINGS FROM NAZE (NORTHERN RYUKUS) AND KAGOSHIMA (KYUSHU) SHOW 500 MB 24 HOUR HEIGHT FALLS BETWEEN 50 AND 100 METERS. MODEL GUIDANCE HAS BEEN HANDLING THIS PROCESS VERY WELL. TY 08W IS A VERY LARGE STORM, WITH VIGOROUS CONVECTIVE BANDING EXTENDING HUNDREDS OF MILES AWAY FROM THE CENTER. THE OUTERMOST RAINBANDS ARE ALREADY SHOWING ON SHIKOKU RADAR IMAGERY. ON THE SOUTHERN SIDE OF THE STORM, THE 170000Z PGTW GRADIENT LEVEL STREAMLINE ANALYSIS REVEALED A LINE OF CONVERGENCE FEEDING INTO THE STORM THAT BEGINS OVER MINDANAO. OVER THE NORTHERN SEMICIRCLE, GALE FORCE WINDS EXTEND FOR NEARLY 250 NM. SURFACE REPORTS FROM NAHA, OVER 360 NM AWAY FROM THE STORM'S CENTER, SHOW STEADY 15-20 KNOT NORTHERLIES. 3. FORECAST REASONING A. THERE IS NO SIGNIFICANT CHANGE IN FORECAST PHILOSOPHY. B. TY 08W WILL CONTINUE ITS CHURN ALONG THE WESTERN PERIPHERY OF THE RIDGE DURING THE NEXT 36 HOURS. TY 08W WILL REMAIN IN VERY FAVORABLE ENVIRONMENTAL CONDITIONS, AND NOW THAT THE ERC IS COMPLETED, WILL RESUME INTENSIFICATION. 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 24, JUST BEFORE MA-ON CRESTS THE RIDGE AXIS. THE RIDGE AXIS WILL EXTEND ALONG THE 29TH LATITUDE. GUIDANCE IS IN EXCELLENT AGREEMENT REGARDING BOTH TRACK AND SPEED, AND ENSEMBLE FORECASTS ARE SHOWING TIGHT PACKING. THE JTWC FORECAST STAYS CLOSE TO CONSENSUS THROUGH TAU 48. AFTER TAU 48, THE JTWC TRACK MOVES FASTER THAN CONSENSUS, WHICH IS BEING SLOWED BY EGRR AND THE BAROTROPIC MODEL. LAND INTERACTION WITH THE RUGGED TERRAIN OF KYUSHU AND SHIKOKU AND BOUNDARY LAYER CONVERGENCE WILL BE THE PRIMARY WEAKENING FORCES. C. DUE TO THE LACK OF A STRONG MID-LATITUDE SHORTWAVE TROUGH AND WESTERLIES ALOFT, THE RE-CURVE IS UNUSUAL IN THAT THE SYSTEM WILL TRACK AT RELATIVELY SLOW SPEEDS AND WEAKEN ONLY SLOWLY AS IT TRACKS SOUTH OF HONSHU. EXTRATROPICAL TRANSITION WILL NOT EVEN BEGIN UNTIL THE SYSTEM IS EAST OF THE CHIBA PENINSULA. GUIDANCE IN THE EXTENDED TAUS HAS REMAINED VERY CONSISTENT OVER THE PAST DAYS AND HAS LOCKED IN REGARDING A PASSAGE SEAWARD OF THE KANTO. TY 08W WILL BE ON A DOWNWARD TREND AS IT PASSES, BUT INTENSITY GUIDANCE INDICATES IT WILL REMAIN ABOVE TYPHOON STRENGTH AS IT DOES SO. THERE IS HOWEVER A GOOD DEAL OF UNCERTAINTY REGARDING THE INTENSITY BETWEEN TAU 72 AND 120, AS THE DEGREE AND DURATION OF LAND INTERACTION WILL MAKE A TREMENDOUS DIFFERENCE IN HOW MUCH OF THE STORM IS LEFT TO DECAY AS IT TRACKS PAST THE KANTO. A 30 MILE DEVIATION FROM TRACK IN EITHER DIRECTION WILL RESULT IN SHARPLY DISPARATE OUTCOMES, ONE WITH EXTENSIVE LAND INTERACTION AND SHARP WEAKENING AND THE OTHER WITH TY 08W GETTING GOOD SUPPORT FROM WARM WATER AND WEAKENING ONLY SLOWLY. UNCERTAINTY IN THE INTENSITY FORECAST WILL EXIST UNTIL THE STORM IS CLEAR OF THE WAKAYAMA PENINSULA.// NNNN