WTPS31 PGTW 082100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18P (DONNA) WARNING NR 021// RMKS/ 1. TROPICAL CYCLONE 18P (DONNA) 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: 081800Z --- NEAR 18.7S 166.1E MOVEMENT PAST SIX HOURS - 150 DEGREES AT 08 KTS POSITION ACCURATE TO WITHIN 040 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 065 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 100 NM NORTHEAST QUADRANT 115 NM SOUTHEAST QUADRANT 085 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 130 NM NORTHEAST QUADRANT 175 NM SOUTHEAST QUADRANT 150 NM SOUTHWEST QUADRANT 105 NM NORTHWEST QUADRANT REPEAT POSIT: 18.7S 166.1E --- FORECASTS: 12 HRS, VALID AT: 090600Z --- 20.0S 166.9E MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 070 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 045 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 145 NM NORTHEAST QUADRANT 155 NM SOUTHEAST QUADRANT 125 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 145 DEG/ 10 KTS --- 24 HRS, VALID AT: 091800Z --- 21.6S 168.0E MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 010 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 005 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 025 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 015 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 140 NM NORTHEAST QUADRANT 145 NM SOUTHEAST QUADRANT 090 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 140 DEG/ 13 KTS --- 36 HRS, VALID AT: 100600Z --- 23.6S 169.7E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 135 NM NORTHEAST QUADRANT 145 NM SOUTHEAST QUADRANT 065 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 140 DEG/ 14 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 101800Z --- 25.7S 171.6E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING EXTRATROPICAL RADIUS OF 034 KT WINDS - 110 NM NORTHEAST QUADRANT 110 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 140 DEG/ 15 KTS --- 72 HRS, VALID AT: 111800Z --- 30.3S 175.8E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY EXTRATROPICAL --- REMARKS: 082100Z POSITION NEAR 19.0S 166.3E. TROPICAL CYCLONE (TC) 18P (DONNA), LOCATED APPROXIMATELY 139 NM WEST- SOUTHWEST OF PORT VILA, VANUATU, HAS TRACKED SOUTH-SOUTHEASTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS TC 18P WEAKENING WITH ASYMMETRIC CONVECTIVE BANDING. THE CURRENT INTENSITY IS ASSESSED AT 100 KNOTS WHICH IS HEDGED ON THE LOWER END OF THE PGTW DVORAK FIX OF T5.5. THE SYSTEM IS CURRENTLY IN AN AREA OF LOW VERTICAL WIND SHEAR (VWS), HIGH SEA SURFACE TEMPERATURES (SSTS 27-28C), AND HAS STRONG POLEWARD OUTFLOW WITH WEAKER EQUATORWARD OUTFLOW. TC 18P IS FORECAST TO TRACK SOUTH-SOUTHEASTWARD FOR THE DURATION OF THE FORECAST PERIOD UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE LOCATED TO THE EAST. AS TC DONNA TRACKS TO THE SOUTH IT WILL MOVE INTO AN AREA OF COOLER SSTS AND INCREASING VWS ASSOCIATED WITH A STRONG SHORTHWAVE TROUGH THAT WILL CONTINUE TO ERODE THE CYCLONE. THE INTERACTION WITH THE TROUGH AND ITS ASSOCIATED BAROCLINIC ZONE WILL CONCURRENTLY CAUSE THE SYSTEM TO BEGIN EXTRA-TROPICAL TRANSITION WHICH WILL BE COMPLETED BY THE END OF THE FORECAST PERIOD. THE DYNAMIC GUIDANCE IS IN GOOD AGREEMENT LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 081800Z IS 30 FEET. NEXT WARNINGS AT 090300Z, 090900Z, 091500Z AND 092100Z.//