WTXS31 PGTW 111500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 26S (SEROJA) WARNING NR 029// RMKS/ 1. TROPICAL CYCLONE 26S (SEROJA) WARNING NR 029 01 ACTIVE TROPICAL CYCLONE IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 111200Z --- NEAR 28.3S 114.4E MOVEMENT PAST SIX HOURS - 135 DEGREES AT 31 KTS POSITION ACCURATE TO WITHIN 020 NM POSITION BASED ON EYE FIXED BY A COMBINATION OF SATELLITE, RADAR AND SYNOPTIC DATA PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 065 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 115 NM NORTHEAST QUADRANT 100 NM SOUTHEAST QUADRANT 055 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT REPEAT POSIT: 28.3S 114.4E --- FORECASTS: 12 HRS, VALID AT: 120000Z --- 32.4S 119.8E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING EXTRATROPICAL VECTOR TO 24 HR POSIT: 125 DEG/ 33 KTS --- 24 HRS, VALID AT: 121200Z --- 36.2S 126.2E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY EXTRATROPICAL --- REMARKS: 111500Z POSITION NEAR 29.3S 115.8E. 11APR21. TROPICAL CYCLONE 26S (SEROJA), LOCATED APPROXIMATELY 360 NM SOUTH OF LEARMONTH, AUSTRALIA, HAS TRACKED SOUTHEASTWARD AT 31 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A WELL DEFINED 10 NM EYE FEATURE JUST CROSSING THE SHORELINE NEAR PORT GREGORY, AUSTRALIA AT THE 111200Z HOUR. SURFACE OBSERVATIONS FROM THE REGION, THE EIR EYE FEATURE AND A WELL-DEFINED RADAR EYE COMBINED TO LEND HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 70 KTS WITH HIGH CONFIDENCE, HEDGED SLIGHTLY LOWER THAN THE AVERAGE OF MULTI- AGENCY DVORAK INTENSITY ESTIMATES OF T4.5 (77 KTS) FROM PGTW AND APRF, BASED ON ANALYSIS OF SURFACE PRESSURE READINGS NEAR 976 MB FROM NEARBY OBSERVATION SITES WHICH SUPPORT AN INTENSITY IN THE 65- 70 KNOT RANGE. PEAK WIND GUSTS OF 65 KTS AT THE GERALDTON AIRPORT PROVIDES ADDITIONAL SUPPORT TO THE INITIAL INTENSITY. TC 26S IS BEING STEERED RAPIDLY TOWARDS THE SOUTHEAST ALONG THE GRADIENT BETWEEN A DEEP-LAYER STR TO THE NORTHEAST AND AN APPROACHING MID- LATITUDE TROUGH TO THE SOUTHWEST. AS THE SYSTEM RACES SOUTHEAST OVER INLAND AUSTRALIA IT IS EXPECTED TO RAPIDLY WEAKEN DUE TO INCREASING SHEAR AND TERRAIN INTERACTION. THE SIMULTANEOUS DEVELOPMENT OF DRY AIR ENTRAINMENT AND THERMAL ADVECTION WILL SIGNAL THE COMMENCEMENT OF EXTRA-TROPICAL TRANSITION (ETT) WITHIN THE NEXT 6-12 HOURS, WITH FULL TRANSITION EXPECTED NO LATER THAN TAU 24, LIKELY BY TAU 18, ALONG THE COAST OF SOUTHERN AUSTRALIA. DYNAMIC MODEL GUIDANCE IS IN VERY GOOD AGREEMENT, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 111200Z IS 28 FEET.// NNNN