WTPS31 PGTW 050900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 23P (NIRAN) WARNING NR 018// RMKS/ 1. TROPICAL CYCLONE 23P (NIRAN) WARNING NR 018 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 050600Z --- NEAR 17.8S 156.8E MOVEMENT PAST SIX HOURS - 120 DEGREES AT 24 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON EYE FIXED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 115 KT, GUSTS 140 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 065 NM NORTHEAST QUADRANT 045 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 115 NM NORTHEAST QUADRANT 085 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 115 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 205 NM NORTHEAST QUADRANT 155 NM SOUTHEAST QUADRANT 115 NM SOUTHWEST QUADRANT 200 NM NORTHWEST QUADRANT REPEAT POSIT: 17.8S 156.8E --- FORECASTS: 12 HRS, VALID AT: 051800Z --- 20.0S 161.2E MAX SUSTAINED WINDS - 120 KT, GUSTS 145 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 040 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 090 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 240 NM NORTHEAST QUADRANT 170 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 190 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 120 DEG/ 25 KTS --- 24 HRS, VALID AT: 060600Z --- 22.4S 165.9E MAX SUSTAINED WINDS - 110 KT, GUSTS 135 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 080 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 230 NM NORTHEAST QUADRANT 160 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 160 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 120 DEG/ 26 KTS --- 36 HRS, VALID AT: 061800Z --- 24.7S 170.9E MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 064 KT WINDS - 020 NM NORTHEAST QUADRANT 010 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 060 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 200 NM NORTHEAST QUADRANT 150 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 140 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 110 DEG/ 25 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 070600Z --- 26.4S 176.1E MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 050 KT WINDS - 030 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 160 NM NORTHEAST QUADRANT 110 NM SOUTHEAST QUADRANT 100 NM SOUTHWEST QUADRANT 140 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 105 DEG/ 23 KTS --- 72 HRS, VALID AT: 080600Z --- 28.7S 173.9W MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY SUBTROPICAL RADIUS OF 050 KT WINDS - 060 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 090 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 130 NM NORTHWEST QUADRANT --- REMARKS: 050900Z POSITION NEAR 18.4S 157.9E. 05MAR21. TROPICAL CYCLONE 23P (NIRAN), LOCATED APPROXIMATELY 584 NM WEST-NORTHWEST OF NOUMEA, NEW CALEDONIA, HAS TRACKED EAST- SOUTHEASTWARD AT 24 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE EMERGENCE OF A VERY WELL DEFINED 12NM EYE BY 0600Z. HOWEVER, A 050557Z SSMIS 91H MICROWAVE IMAGE SHOWED THAT THE DEEP CONVECTION DOES NOT EXTEND ALL THE WAY AROUND THE SYSTEM, WITH A DISTINCT BREAK IN THE EYEWALL ON THE SOUTHEASTERN SIDE, INDICATIVE OF INCREASING EASTERLY WIND SHEAR. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON BOTH THE SSMIS MICROWAVE IMAGE AND THE 10NM EYE IN THE INFRARED IMAGERY. THE INITIAL INTENSITY IS ASSESSED AT 115 KNOTS, HEDGED SLIGHTLY LOWER THAN A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF T6.5 (127 KTS) AND CLOSELY ALIGNED TO A 114 KNOT WIND SPEED MEASUREMENT FROM A 050227Z AMSR2 PASS. TC 23P IS RAPIDLY MOVING SOUTHEASTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A COMBINED NEAR EQUATORIAL AND SUBTROPICAL RIDGE COMPLEX CENTERED TO THE NORTHEAST. THE ENVIRONMENT REMAINS FAVORABLE FOR THE MOMENT WITH MODERATE (20-25 KT) VWS BEING OFFSET BY VERY STRONG POLEWARD OUTFLOW AND WARM (29C) SSTS. THE SYSTEM IS FORECAST TO CONTINUE TRACKING SOUTHEASTWARD THROUGH TAU 48 ALONG THE TIGHT GRADIENT BETWEEN THE RIDGE COMPLEX TO THE NORTHEAST AND AN APPROACHING MAJOR SHORTWAVE TROUGH TO THE WEST. BY THE END OF THE FORECAST, THE SYSTEM WILL MOVE SLIGHTLY MORE EASTWARD AS IT COMES UNDER THE STEERING INFLUENCE OF A DYNAMIC LOW TO MID-LEVEL ANTICYCLONE TO THE SOUTH. IN THE NEAR-TERM, GOOD ENVIRONMENTAL CONDITIONS WILL SUPPORT ADDITIONAL INTENSIFICATION TO A PEAK OF 120 KNOTS BY TAU 12. THEREAFTER, ENVIRONMENTAL CONDITIONS BEGIN TO RAPIDLY DETERIORATE AS THE VWS INCREASES TO AN EXTENT THAT THE OUTFLOW CANNOT OVERCOME AND THE CORE BECOMES DISRUPTED. AFTER TAU 48, VWS WEAKENS SLIGHTLY, BUT DRY AIR ENTRAINMENT AND COOL SSTS AT OR BELOW 26C WILL SERVE TO FURTHER WEAKEN THE SYSTEM AS IT BEGINS SUBTROPICAL TRANSITION. THE TRANSITION TO A STORM FORCE SUBTROPICAL SYSTEM WILL BE COMPLETE NO LATER THAN, AND POSSIBLY EARLIER THAN, TAU 72. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 24 BUT CROSS AND ALONG-TRACK UNCERTAINTY INCREASES SIGNIFICANTLY THEREAFTER. THE JTWC FORECAST LIES NEAR THE CONSENSUS MEAN THROUGH TAU 24, THEN NEAR THE ECMWF TRACK THROUGH THE REMAINDER OF THE FORECAST PERIOD. OVERALL THERE IS HIGH CONFIDENCE IN THE FIRST 24 HOURS OF THE FORECAST, AND LOW CONFIDENCE THEREAFTER. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 050600Z IS 40 FEET. NEXT WARNINGS AT 051500Z, 052100Z, 060300Z AND 060900Z.// NNNN