WDPN33 PGTW 172100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W (NANMADOL) WARNING NR 021// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 28.5N 131.4E INITIAL INTENSITY: 115 KTS GEOGRAPHIC REFERENCE: 226 NM EAST-NORTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 48 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY CLEARLY SHOWS THAT TY 16W HAS EMBARKED ON A FAIRLY RAPID WEAKENING TREND. AT THE 1800Z HOUR, THE RAGGED EYE WAS MEASURED AT 9-NM IN THE EIR BUT BY THE 1900Z HOUR THE EYE HAD FILLED AND NO LONGER DISCERNABLE. ANIMATED RADAR DATA INDICATES THE LOW LEVEL EYE REMAINS WELL-DEFINED, THOUGH THE INNER EYEWALL IS WEAKENING AND SHRINKING AND IS NOW OPEN ON THE WESTERN SIDE. THE SECONDARY EYEWALL THAT DEVELOPED OVER THE PAST 24 HOURS DURING THE EYEWALL REPLACEMENT CYCLE (ERC) IS ALSO BEGINNING TO BECOME MORE RAGGED. ALL THIS TO SAY, TY 16W HAS DEFINITELY PASSED ITS PRIME. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 9-NM EYE IN THE EIR AS WELL AS RJTD RADAR FIX POSITIONS AND A 171824Z GMI 89GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS LOWERED TO 115 KNOTS WITH HIGH CONFIDENCE BASED ON CONCURRENCE OF THE BULK OF AGENCY AND OBJECTIVE ESTIMATES. THE SATCON REMAINS UNREASONABLY HIGH DUE TO AN UNLIKELY 145 KNOT AMSU-B SOUNDER ESTIMATE. THE SYSTEM IS GENERALLY MOVING NORTHWESTWARD AT A STEADY 9 KNOT THROUGH THE 1800Z HOUR, BEFORE RADAR INDICATED A PRONOUNCED SLOW-DOWN AND WOBBLE TO THE RIGHT. THE ENVIRONMENT IS BECOMING STEADILY LESS FAVORABLE, FOR WHILE BULK SHEAR IS LOW, AND OUTFLOW IS IMPROVING TO POLEWARD, THE SYSTEM HAS TRACKED OVER A PATCH OF LOW OHC WATER, IS STILL STRUGGLING WITH THE ERC AND AS SHOWN IN THE NAZE 1200Z SOUNDING, A FIST OF ELEVATED MID-LEVEL WESTERLY FLOW IS IMPARTING SOME CONVERGENT FLOW ON THE WEST SIDE. THIS IS CONFIRMED BY LATE RECEIPT OF A 171921Z SSMIS 91GHZ MICROWAVE IMAGE SHOWING SIGNIFICANT EROSION OF THE OUTER CONVECTIVE BANDS ON THE WEST SIDE. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS RJTD: T5.5 - 102 KTS KNES: T6.0 - 115 KTS CIMSS SATCON: 128 KTS AT 171727Z CIMSS ADT: 115 KTS AT 171740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 0-5 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: INCREASING POLEWARD OUTFLOW, STRONG MID-LEVEL WESTERLY FLOW. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY 16W IS BEGINNING TO ROUND THE AXIS OF THE STEERING RIDGE TO THE EAST AND WILL GRADUALLY START TO TURN NORTHWARD TOWARDS THE WESTERN COAST OF KYUSHU OVER THE NEXT 12 HOURS. THE RECENT SLOWDOWN AND SHARP WOBBLE TO THE EAST SEEN IN THE RADAR IMAGERY ARE CONCERNING BUT AT THIS POINT THE TRACK FORECAST REMAINS NORTH-NORTHWEST TURNING TO THE NORTH BY TAU 24. THE SYSTEM IS FORECAST TO PASS CLOSE BY YAKUSHIMA ISLAND, THEN MAKE LANDFALL ALONG THE SOUTHERN TIP OF KYUSHU BY TAU 12, THEN SKIRT THE WEST COAST OF KYUSHU TO A POINT NEAR NAGASAKI BY TAU 24. AT THIS POINT THE SYSTEM HAS REACHED THE RIDGE AXIS AND WILL TURN SHARPLY NORTHEASTWARD AHEAD OF A FAST-APPROACHING UPPER-LEVEL TROUGH AND ACCOMPANYING SURFACE COLD FRONT DRAPED ACROSS THE SEA OF JAPAN. BY TAU 36 THE CENTER OF THE RAPIDLY WEAKENING SYSTEM WILL BE FOUND NEAR IWAKUNI, ACCELERATING QUICKLY OFF TO THE NORTHEAST ALONG THE JAPANESE ALPS. THE CENTER OF THE SYSTEM IS FORECAST TO REMAIN GENERALLY TO THE SOUTH AND EAST OF THE SPINE OF THE JAPANESE ALPS, AND REEMERGE INTO THE PACIFIC OCEAN BY TAU 72, AND QUICKLY SCOOTING OUT INTO THE NORTH PACIFIC BY THE END OF THE FORECAST PERIOD. EVEN THOUGH THE SYSTEM IS BEGINNING TO TAP INTO SOME STRONG POLEWARD OUTFLOW, TY 16W IS UNLIKELY TO RECOVER FROM THE EFFECTS OF THE ONGOING ERC AND THE IMPACTS OF THE WESTERLY MID-LEVEL CONVERGENCE AND FUTURE TERRAIN INFLUENCES, AND THE FORECAST CALLS FOR STEADY WEAKENING DOWN TO 90 KNOTS BY TAU 24. ONCE THE SYSTEM MAKES ITS TURN TO THE NORTHEAST, IT WILL QUICKLY BE TORN APART BY THE COMBINATION OF THE ELEVATED TERRAIN AND VERY STRONG SHEAR INDUCED BETWEEN DIRECTLY OPPOSING LOW-LEVEL AND UPPER-LEVEL FLOW. WHAT REMAINS OF THE LOW LEVEL CIRCULATION WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 48 AS THE SYSTEM SLIDES NORTHEAST ALONG THE FRONTAL BOUNDARY. FULL ETT IS EXPECTED NO LATER THAN TAU 96, THOUGH THE SYSTEM IS EXPECTED TO RELATIVELY WEAK BY THIS POINT. MODEL DISCUSSION: REGARDLESS OF THE RECENTLY OBSERVED WOBBLE, MODEL GUIDANCE IS IN VERY TIGHT AGREEMENT TO TAU 12, WITH ALL DETERMINISTIC AND ENSEMBLE MEMBERS SUPPORTING THE JTWC FORECAST TRACK. IN LINE WITH PREVIOUS FORECAST, THINGS GET SPOTTY AFTER TAU 24 AS THE MODELS DIVERGE SIGNIFICANTLY IN HOW THEY HANDLE THE BAROCLINIC ZONE INTERACTION AND THE RATE OF WEAKENING AND THEN ENSUING TRACK. GENERALLY, THE MODELS SPLIT INTO TWO CAMPS AFTER TAU 36; THE FIRST CONSISTS OF THE FAST MODELS INCLUDING GALWEM, UKMET, UKMET ENSEMBLE AND JGSM. THESE MODELS SHOW THE SYSTEM RACING TO THE NORTHEAST ON THE NORTH SIDE OF THE JAPANESE ALPS, EVEN TAKING THE SYSTEM OVER WATER IN THE SOJ FOR A WHILE, THEN CROSS THE COAST AGAIN NEAR MISAWA AND FOR THE MOST PART DISSIPATE THE SYSTEM BY TAU 72 FAR TO THE NORTHEAST OF HOKKAIDO. THE SECOND GROUP OF SLOWER MODELS CONSISTS OF GFS, NAVGEM, ECMWF AND THEIR ENSEMBLES AND THE HWRF. IN THIS GROUP, THE SYSTEM SLIDES TO THE NORTHEAST, AT A SLOWER PACE AND REMAINS SOUTH OF THE ALPS BEFORE MOVING INTO THE PACIFIC TO A POINT EAST OF HOKKAIDO BY TAU 96. THE ECMWF IS THE EXTREME OUTLIER OF THIS GROUP, INSISTING ON EARLY DISSIPATION AND A TRACK TO THE SOUTH OF TOKYO BY TAU 72. THE RESULTING ALONG-TRACK SPREAD IN THE GUIDANCE PACKAGE IS EXTREME, WELL OVER 1000NM. THE JTWC FORECAST REMAINS GENERALLY CONSISTENT WITH THE PREVIOUS, THOUGH IT DOES SHIFT THE TRACK SOUTH OF THE ALPS. CONFIDENCE IS LOW THROUGH THE FORECAST PERIOD. INTENSITY GUIDANCE IS BETTER BEHAVED FOR THE MOST PART, WITH ALL MODELS SHOWING A SHARP WEAKENING THROUGH THE PERIOD. THE JTWC FORECAST LIES ON THE HIGH EDGE OF THE PACKAGE THROUGH THE FORECAST WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN