WDPN31 PGTW 042100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 031// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 28.6N 124.7E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 450 NM SOUTH-SOUTHWEST OF BUSAN, SOUTH KOREA MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 46 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SOMEWHAT RAGGED STRUCTURE OVERALL, THOUGH TY 12W HAS SUCCESSFULLY MAINTAINED AN 8-NM EYE CENTERED WITHIN AN APPROXIMATELY 80-NM DIAMETER CDO. OVERNIGHT MICROWAVE IMAGERY AND A 04XXXXZ AMSR2 91GHZ IMAGE INDICATE EROSION OF THE LARGE SECONDARY EYEWALL THAT WAS PRESENT YESTERDAY AS WELL AS THE EXTREMELY SMALL CONVECTIVE CORE OF TY 12W, WHICH REMAINS RELATIVELY ISOLATED WITH LIMITED CONVECTIVE BANDING. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 8-NM IN THE EIR AND AGREEMENT OF AGENCY FIX POSITIONS. REANALYSIS OF A 040934Z RADARSAT-2 SAR IMAGE RESULTED IN A SLIGHT INCREASE OF THE 0600Z AND 1200Z INTENSITIES TO 110 KNOTS (THE SAR FIX WAS 113 KNOTS), HEDGED ABOUT 5-10 KNOTS HIGHER THAN THE SUBJECTIVE AND OBJECTIVE FIXES AT THAT TIME. NOT MUCH HAS CHANGED IN THE FIX DATA OVER THE PAST 12 HOURS, WITH EXCUSIONS ABOVE AND BELOW THE AVERAGE T5.5, BUT DUE THE COMPACT NATURE OF THE SYSTEM AND PINHOLE EYE, DVORAK-BASED INTENSITY ESTIMATES ARE LIKELY A BIT TOO LOW, SO THE INITIAL INTENSITY REMAINS SET AT 110 KNOTS, EXTRAPOLATING FROM THE SAR FIX. THE SYSTEM IS MOVING GENERALLY NORTHWARD BUT HAS SHOWN SOME FAIRLY EXTREME TROCHOIDAL MOTION OVER THE PAST 6-12 HOURS AS IT WOBBLES ITS WAY NORTH. THE ENVIRONMENT REMAINS FAVORABLE, WITH WARM SSTS AND LOW SHEAR (JUST 3 KNOTS IN THE LATEST CIMSS ANALYSIS). ON TOP OF THAT, UPPER-LEVEL OUTFLOW HAS EXPANDED TO THE WEST AND THE SYSTEM HAS NOW ESTABLISHED A POLEWARD CHANNEL INTO THE NOSE OF STRONG JET MAX OVER THE BOHAI GULF. DRY AIR INTRUSION FROM THE WEST IS STILL AN ISSUE IN THE LOW TO MID-LEVELS, AS EVIDENCED BY A CLEAR SLOT THAT IS WRAPPING ALL THE WAY AROUND THE SYSTEM AND IMPINGING ON THE CORE FROM THE WEST. INITIAL WIND RADII BASIS: SAR AND SCATTEROMETER DATA CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS RJTD: T5.5 - 102 KTS KNES: T5.5 - 102 KTS CIMSS SATCON: 105 KTS AT 041723Z CIMSS ADT: 100 KTS AT 041810Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG POLEWARD AND EQUATORWARD OTHER FACTORS: LOW TO MID-LEVEL DRY AIR INTRUSION ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY 12W WILL CONTINUE TRACKING GENERALLY NORTHWARD IN THE NEAR-TERM, BUT IS EXPECTED TO TURN OVER TOWARDS THE NORTHEAST BY TAU 12 AS IT BEGINS TO ROUND THE RIDGE AXIS AND ACCELERATES NORTHEASTWARD TOWARDS THE KOREAN PENINSULA. LANDFALL IS EXPECTED ALONG THE SOUTHERN COAST OF KOREA NEAR BUSAN AROUND TAU 30. FROM AN INTENSITY PERSPECTIVE, THE SYSTEM STILL HAS A SHORT WINDOW IN WHICH CONDITIONS WILL REMAIN FAVORABLE FOR INTENSIFICATION. WITH THE SECONDARY EYEWALL HAVING ERODED, THERE IS MUCH LESS PROBABILITY OF AN EYEWALL REPLACEMENT CYCLE AT THIS POINT, WITH THE M-PERC PROBABILITIES TAKING A NOSEDIVE OVERNIGHT, NOW DOWN TO LESS THAN 10 PERCENT. HAVING ESTABLISHED A GOOD POLEWARD OUTFLOW CHANNEL, WHICH WILL ONLY IMPROVE OVER TIME, AND A BUFFER OF ENHANCED OUTFLOW TO THE WEST BLOCKING ANY IMPINGING WESTERLY FLOW FROM THAT SECTOR, SHEAR LOOKS TO REMAIN LOW FOR A LEAST THE NEXT 12 HOURS. THE MAIN IMPEDIMENT WILL BE THE STUBBORN LOW TO MID-LEVEL DRY AIR WHICH CONTINUES TO BE PULLED OFF THE CHINESE MAINLAND AND INTO THE CORE OF THE SYSTEM. IF IT CAN FIGHT OFF THE DRY AIR, TY 12W STILL HAS A SHORT WINDOW OF FAVORABLE CONDITIONS TO INTENSIFY A BIT MORE, LIKELY PEAKING WITHIN THE NEXT 6 TO 12 HOURS. BUT AFTER TAU 12 TY 12W WILL BEGIN TO INTERACT WITH AN APPROACHING MID-LATITUDE TROUGH WITH STRONG DYNAMIC SUPPORT INCLUDING A ROBUST JET MAX AND NEGATIVELY TILTED 500MB TROUGH. BY TAU 24, JUST EAST OF CHEJU DO, THE SYSTEM WILL MOVE OVER SIGNIFICANTLY COOLER WATERS, BE ASSAULTED BY VERY DRY AIR IN THE MID-LEVELS AND STARTS TO BE DECAPITATED BY VERY STRONG WESTERLY SHEAR. THE SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 24 OR SHORTLY THEREAFTER AS IT BEGINS TO COUPLE WITH THE SOUTHERN END OF THE UPPER-LEVEL TROUGH. WHILE THE SYSTEM WILL RAPIDLY LOSE ITS TROPICAL CHARACTERISTICS AND BE SHEARED APART AS IT MOVES OVER THE SOUTHERN KOREAN PENINSULA, THE STRONG BAROCLINC FORCING ASSOCIATED WITH THE MID-LATITUDE SYSTEM WILL RESULT HIGHER INTENSITIES THAN OTHERWISE EXPECTED FROM A WEAKENING TROPICAL CYCLONE. BETWEEN TAUS 36 AND 48, THE SYSTEM WILL LOSE ALL OF ITS REMAINING TROPICAL CHARACTERISTICS AND BECOME A TYPHOON-STRENGTH EXTRA-TROPICAL LOW IN THE NORTHERN SEA OF JAPAN. MODEL DISCUSSION: TRACK GUIDANCE, WITH THE CONTINUED EXCEPTION OF THE JGSM, REMAINS IN VERY TIGHT AGREEMENT THROUGH THE FORECAST PERIOD, WITH JUST A 50-NM SPREAD AS THE SYSTEM CROSSES THE COAST OF SOUTH KOREA. THE ENVELOPE EXPANDS BOTH ACROSS AND ALONG-TRACK AS THE SYSTEM GOES EXTRA-TROPICAL, BUT STILL REMAINS IN GOOD AGREEMENT, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE HAS COME INTO BETTER AGREEMENT SINCE THE PREVIOUS RUN, THOUGH THERE REMAIN TWO DISTINCT GROUPINGS THROUGH ABOUT TAU 36. THE HWRF AND DECAY-SHIPS (GFS AND NVGM) MODELS CONCUR IN A STEADY-STATE INTENSITY TO TAU 12, FOLLOWED BY SHARP AND STEADY WEAKENING THROUGH THE REMAINDER OF THE FORECAST. MEANWHILE THE COAMPS-TC AND GFS SHOW SHARP WEAKENING FROM TAU 00. AS DISCUSSED ABOVE, THE SYSTEM WILL LIKELY PEAK IN THE NEXT 6 TO 12 HOURS BUT THEN BEGIN TO WEAKEN AGAIN BY TAU 12 RESULTING IN A STEADY-STATE INTENSITY FORECAST AT TAU 12. THE JTWC FORECAST TRACKS THE HWRF, SHIPS AND CONSENUS GUIDANCE CLOSELY THROUGH THE FORECAST PERIOD, AND LIES ALONG THE HIGHER EDGE OF THE GUIDANCE ENVELOPE, WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: --- INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: --- // NNNN