WTPS32 PGTW 202100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18P (NATHAN) WARNING NR 021// RMKS/ 1. TROPICAL CYCLONE 18P (NATHAN) WARNING NR 021 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 201800Z --- NEAR 14.0S 141.5E MOVEMENT PAST SIX HOURS - 290 DEGREES AT 08 KTS POSITION ACCURATE TO WITHIN 040 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY REPEAT POSIT: 14.0S 141.5E --- FORECASTS: 12 HRS, VALID AT: 210600Z --- 13.5S 139.7E MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 020 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 065 NM NORTHEAST QUADRANT 065 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 290 DEG/ 09 KTS --- 24 HRS, VALID AT: 211800Z --- 12.9S 138.0E MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 010 NM NORTHEAST QUADRANT 010 NM SOUTHEAST QUADRANT 010 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 025 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 065 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 295 DEG/ 07 KTS --- 36 HRS, VALID AT: 220600Z --- 12.3S 136.7E MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 48 HR POSIT: 295 DEG/ 07 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 221800Z --- 11.7S 135.4E MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 015 NM NORTHEAST QUADRANT 015 NM SOUTHEAST QUADRANT 015 NM SOUTHWEST QUADRANT 015 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 055 NM NORTHEAST QUADRANT 045 NM SOUTHEAST QUADRANT 045 NM SOUTHWEST QUADRANT 055 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 285 DEG/ 04 KTS --- 72 HRS, VALID AT: 231800Z --- 11.3S 133.7E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 250 DEG/ 05 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 241800Z --- 11.9S 131.8E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 120 HR POSIT: 240 DEG/ 05 KTS --- 120 HRS, VALID AT: 251800Z --- 13.0S 129.9E MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 202100Z POSITION NEAR 13.9S 141.0E. TROPICAL CYCLONE (TC) 18P (NATHAN), LOCATED APPROXIMATELY 291 NM EAST-SOUTHEAST OF GOVE AIRPORT, AUSTRALIA, HAS TRACKED WEST- NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS DIMINISHING DEEP CONVECTION OVER A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION AS IT CROSSES THE CAPE YORK PENINSULA. THE CURRENT POSITION IS BASED ON SATELLITE FIXES FROM PGTW, KNES AND ABRF AS WELL AS THE RADAR LOOP FROM WEIPA. THE INITIAL INTENSITY IS ASSESSED AT 40 KNOTS BASED ON AN OVERALL ASSESSEMENT OF THE CURRENT STRUCTURE AND SURFACE OBSERVATIONS FOR QUEENSLAND FROM AUSTRALIA BUREAU OF METEOROLOGY. UPPER-LEVEL ANALYSIS INDICATES TC 18P REMAINS IN FAVORABLE ENVIRONMENT WITH A POINT-SOURCE DIRECTLY OVER THE SYSTEM AND LOW (05 TO 10 KNOT) VERTICAL WIND SHEAR. TC NATHAN CONTINUES TO TRACK ALONG THE NORTHERN PERIPHERY OF A DEEP LAYER SUB-TROPICAL RIDGE (STR) LOCATED OVER CENTRAL AUSTRALIA. UPON RE-EMERGING OVER WATER IN THE GULF OF CARPENTARIA, TC 18P IS EXPECTED TO REINTENSIFY AS FAVORABLE CONDITIONS PERSIST. THE SYSTEM IS EXPECTED TO MAKE A SECOND LANDFALL AROUND TAU 36 AND BEGIN ITS WEAKENING TREND. AVAILABLE MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 LENDING HIGH CONFIDENCE IN THE TRACK FORECAST. HOWEVER, THERE ARE SOME DIFFERENCES IN THE EXTENDED TAUS DUE TO THE EXTENT OF THE STEERING STR. FOR THIS REASON, THERE IS LOW CONFIDENCE IN THE EXTENDED PERIOD OF THE FORECAST. NEXT WARNINGS AT 210900Z AND 212100Z.//