WTPS32 PGTW 220900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18P (NATHAN) WARNING NR 024// RMKS/ 1. TROPICAL CYCLONE 18P (NATHAN) WARNING NR 024 02 ACTIVE TROPICAL CYCLONES IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 220600Z --- NEAR 12.2S 135.9E MOVEMENT PAST SIX HOURS - 295 DEGREES AT 09 KTS POSITION ACCURATE TO WITHIN 025 NM POSITION BASED ON CENTER LOCATED BY A COMBINATION OF SATELLITE AND RADAR PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT WIND RADII VALID OVER OPEN WATER ONLY REPEAT POSIT: 12.2S 135.9E --- FORECASTS: 12 HRS, VALID AT: 221800Z --- 11.5S 134.8E MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 24 HR POSIT: 290 DEG/ 05 KTS --- 24 HRS, VALID AT: 230600Z --- 11.2S 133.9E MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 055 NM NORTHEAST QUADRANT 055 NM SOUTHEAST QUADRANT 065 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 255 DEG/ 04 KTS --- 36 HRS, VALID AT: 231800Z --- 11.4S 133.1E MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 230 DEG/ 05 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 240600Z --- 12.0S 132.3E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 230 DEG/ 05 KTS --- 72 HRS, VALID AT: 250600Z --- 13.2S 130.9E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 96 HR POSIT: 260 DEG/ 05 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 260600Z --- 13.6S 129.0E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 120 HR POSIT: 265 DEG/ 06 KTS --- 120 HRS, VALID AT: 270600Z --- 13.7S 126.5E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY --- REMARKS: 220900Z POSITION NEAR 12.0S 135.6E. TROPICAL CYCLONE 18P (NATHAN), LOCATED APPROXIMATELY 294 NM EAST OF DARWIN, AUSTRALIA, HAS TRACKED WEST-NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED AN OVERALL CONVECTIVE SIGNATURE WITH A SLIGHT WARMING OF THE CENTRAL DENSE OVERCAST (CDO) AS IT DRAGGED JUST OFF THE COAST OF THE NORTHERN TERRITORY. THE INITIAL POSITION IS BASED ON THE ABOVE ANIMATION AND ON A COMPOSITE RADAR LOOP FROM GOVE AIRPORT WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS BASED ON AN OVERALL ASSESSMENT OF AGENCY DVORAK ESTIMATES AND NEARBY SURFACE OBSERVATIONS AND TAKES INTO ACCOUNT THE SLIGHTLY WEAKENED STATE OF THE CYCLONE. UPPER-LEVEL ANALYSIS INDICATES TC NATHAN REMAINS IN A FAVORABLE ENVIRONMENT WITH A POINT-SOURCE ANTICYCLONE DIRECTLY OVERHEAD THAT IS PROVIDING RADIAL OUTFLOW TO THE CDO. TC 18P IS TRACKING ALONG THE NORTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE SOUTH, OVER CENTRAL AUSTRALIA. AFTER TAU 36, THE STR WILL WEAKEN WITH THE APPROACH OF A MIGRATORY MID-LATITUDE TROUGH FROM THE SOUTHWEST. THIS WILL CAUSE TC 18P TO MOMENTARILY TRACK SOUTHWESTWARD INLAND TOWARDS DARWIN BEFORE RETURNING TO A WESTWARD TRAJECTORY AFTER TAU 72 THEN BACK INTO WATER - THIS TIME THE SOUTH INDIAN OCEAN. FAVORABLE UPPER LEVEL CONDITIONS WILL PROMOTE A MODERATE INTENSIFICATION OVER THE NEXT 24 HOURS, PEAKING AT 65 KNOTS BEFORE TRACKING INLAND. TC NATHAN WILL ERODE AS IT DRAGS OVER LAND BUT WILL EMERGE IN THE SOUTH INDIAN OCEAN AT 35 KNOTS AND POISED FOR RE-INTENSIFICATION. AVAILABLE MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT LENDING FAIR CONFIDENCE IN THE JTWC TRACK FORECAST. NEXT WARNINGS AT 222100Z AND 230900Z. REFER TO TROPICAL CYCLONE 20P (REUBEN) WARNINGS (WTPS31 PGTW) FOR 12-HOURLY UPDATES.//