WDPN31 PGTW 022100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 023// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 22.4N 124.7E INITIAL INTENSITY: 75 KTS GEOGRAPHIC REFERENCE: 299 NM SOUTHWEST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 40 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A LARGE CIRCULATION, WITH A RAGGED CORE OF DISORGANIZED CONVECTION. THE CONVECTIVE ENVELOPE IS DISPLACED PRIMARILY TO THE SOUTH AND EAST OF THE ASSESSED LOW LEVEL CENTER (LLC) DUE TO PERSISTENT, THOUGH WEAKENING, NORTHERLY SHEAR. WATER VAPOR IMAGERY SUGGESTS A SMALL ANTICYCLONE OVER TOP OF THE SYSTEM WHICH IS EXPANDING RADIALLY, BUT PARTICULARLY POLEWARD AND EASTWARD, COMPLIMENTING THE ALREADY GOOD EQUATORWARD OUTFLOW. ANIMATED RADAR IMAGERY REVEALS A WELL DEFINED 40NM WIDE EYE FEATURE AND LATER EIR AROUND THE 2000Z HOUR SUGGESTS DEVELOPMENT OF A NASCENT INFRARED EYE. GALE-FORCE WIND RADII HAVE BEEN ADJUSTED, EXPANDING ROUGHLY 100NM FURTHER IN THE SOUTHEAST SECTOR, BUT CONTRACTING IN THE NORTHERN SECTORS, AS SURFACE WINDS REMAIN SUB-GALE FORCE AT BOTH MIYAKOJIMA AND ISIGAKIJIMA. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE RADAR DATA. THE INITIAL INTENSITY OF 75 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY DVORAK CURRENT INTENSITY ESTIMATES, THOUGH DATA-T NUMBERS HAVE LOWERED DOWN TO THE T4.0 RANGE. ADT AND AIDT ESTIMATES HAVE REMAINED FAIRLY STEADY OVER THE PAST SIX HOURS AT 74 AND 75 KNOTS RESPECTIVELY. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS RJTD: T5.0 - 90 KTS KNES: T4.0 - 65 KTS CIMSS SATCON: 82 KTS AT 021711Z CIMSS ADT: 74 KTS AT 021740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: STRONG RADIAL OTHER FACTORS: UPWELLING OF COOLER WATER ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: REGIONAL UPPER-AIR SOUNDINGS AND ANALYSIS SUPPORTS THE MODEL DATA SUGGESTING THE WEAKENING OF THE STR OVER CHINA, AND THE STRENGTHENING OF THE STR TO THE EAST, WITH THE STEERING GRADIENT TIGHTENING UP ON THE EASTERN SIDE OF TY 12W. THE RESULT IS THAT THE STR TO THE EAST HAS NOW ASSUMED THE PRIMARY STEERING ROLE, AND IS STARTING TO KICK TY 12W OUT OFF TO THE NORTH, THOUGH SLOWLY FOR THE TIME BEING. THE SYSTEM IS EXPECTED TO TRACK RATHER SLOWLY NORTHWARD OVER THE NEXT 24 HOURS AS IT PASSES JUST EAST OF ISHIKAGIJIMA, THEN WILL ACCELERATE NORTHWARD INTO THE EAST CHINA SEA AS THE RIDGE CONTINUES TO BUILD TO THE EAST. A SHARP TURN TO THE NORTHEAST IS FORECAST TO START BY TAU 48 AS THE RIDGE GETS PUSHED TO THE NORTHEAST BY THE APPROACH OF A MAJOR MID-LATITUDE TROUGH FROM THE WEST. THE SYSTEM WILL PASS OVER THE SOUTHERN PORTION OF SOUTH KOREA AND MOVE RAPIDLY INTO THE SEA OF JAPAN BY TAU 96. WHILE THE UPPER-LEVEL ENVIRONMENT IS STEADILY IMPROVING, THE SLOW FORWARD MOTION OF TY 12W MEANS THAT IT WILL REMAIN OVER RELATIVELY COOL WATERS, BROUGHT ON BY THE RECENT UPWELLING EVENT, FOR ABOUT 12 HOURS OR SO, INHIBITING SIGNIFICANT INTENSIFICATION IN THE NEAR-TERM. ONCE IT MOVES TO THE NORTH OF THE RYUKUS HOWEVER, MORE RAPID INTENSIFICATION IS EXPECTED AS THE SYSTEM WILL TAP INTO A POLEWARD OUTFLOW CHANNEL AHEAD OF THE APPROACHING MID-LATITUDE TROUGH, REACHING A PEAK OF 105 KNOTS BY TAU 48. AFTER THE SYSTEM TURNS NORTHEASTWARD TOWARDS KOREA, IT WILL BEGIN TO FEEL THE EFFECTS OF DECREASING SSTS AND INCREASING SHEAR, WHICH WILL BEGIN TO WEAKEN THE SYSTEM, DOWN TO 85 KNOTS BY TAU 72. AT THIS POINT THE SYSTEM WILL BEGIN TO INTERACT WITH THE MID-LATITUDE WESTERLY FLOW AND BEGIN EXTRA-TROPICAL TRANSITION (ETT), WITH THE SYSTEM TRANSITIONING TO A STORM-FORCE EXTRA-TROPICAL LOW IN THE SEA OF JAPAN NO LATER THAN TAU 96. MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH THE DURATION OF THE FORECAST, WITH 100NM TO 150NM SPREAD FROM TAU 48 TO 72. ALONG-TRACK SPREAD INCREASES SIGNIFICANTLY AFTER TAU 72 AS THE SYSTEM UNDERGOES ETT. ENSEMBLE GUIDANCE DEPICTS A BIT MORE UNCERTAINTY WITH THIS RUN, WITH THE ECENS ENVELOPE NOW EXTENDING FROM COASTAL CHINA TO ABOUT 126E, MUCH LARGER THAN WITH PREVIOUS RUNS. THE GEFS ENVELOPE HAS ALSO EXPANDED, BUT REMAINS MORE TIGHTLY CONFINED THAN ECENS. OVERALL CONFIDENCE IS HIGH UP THROUGH TAU 48 BUT THEN DECREASES FAIRLY QUICKLY TO MEDIUM IN THE LONGER-TERM. COAMPS-TC ENSEMBLE INTENSITY GUIDANCE SUGGESTS A HIGH LIKELIHOOD OF MODERATE INTENSIFICATION, WITH ABOUT THIRTY PERCENT CHANCE OF RAPID INTENSIFICATION AROUND TAU 36 TO TAU 48. THE REMAINDER OF THE DETERMINISTIC GUIDANCE IS CONSTRAINED BETWEEN 90 TO 120 KNOTS, WITH COAMPS-TC ON THE HIGH END AND THE CONSENSUS MEAN ON THE LOW SIDE, THOUGH THIS IS BEING PULLED LOW DUE TO THE UNREALISTIC DECAY-SHIPS GUIDANCE WHICH SHOWS NO FURTHER INTENSIFICATION IN THE FORECAST PERIOD. THE JTWC FORECAST LIES CLOSE TO THE HWRF SOLUTION, ABOVE THE CONSENSUS, WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN