WTPS31 PGTW 070900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18P (DONNA) WARNING NR 015// RMKS/ 1. TROPICAL CYCLONE 18P (DONNA) WARNING NR 015 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 070600Z --- NEAR 14.6S 164.6E MOVEMENT PAST SIX HOURS - 150 DEGREES AT 08 KTS POSITION ACCURATE TO WITHIN 015 NM POSITION BASED ON EYE FIXED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 025 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 060 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 065 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 160 NM NORTHEAST QUADRANT 155 NM SOUTHEAST QUADRANT 160 NM SOUTHWEST QUADRANT 125 NM NORTHWEST QUADRANT REPEAT POSIT: 14.6S 164.6E --- FORECASTS: 12 HRS, VALID AT: 071800Z --- 16.3S 164.9E MAX SUSTAINED WINDS - 095 KT, GUSTS 115 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 055 NM NORTHEAST QUADRANT 055 NM SOUTHEAST QUADRANT 045 NM SOUTHWEST QUADRANT 045 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 095 NM NORTHEAST QUADRANT 100 NM SOUTHEAST QUADRANT 075 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 190 NM NORTHEAST QUADRANT 200 NM SOUTHEAST QUADRANT 175 NM SOUTHWEST QUADRANT 125 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 165 DEG/ 08 KTS --- 24 HRS, VALID AT: 080600Z --- 17.8S 165.3E MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 055 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 095 NM NORTHEAST QUADRANT 110 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 190 NM NORTHEAST QUADRANT 215 NM SOUTHEAST QUADRANT 170 NM SOUTHWEST QUADRANT 110 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 160 DEG/ 09 KTS --- 36 HRS, VALID AT: 081800Z --- 19.4S 166.0E MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 045 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 045 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 085 NM NORTHEAST QUADRANT 095 NM SOUTHEAST QUADRANT 075 NM SOUTHWEST QUADRANT 055 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 165 NM NORTHEAST QUADRANT 210 NM SOUTHEAST QUADRANT 150 NM SOUTHWEST QUADRANT 100 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 145 DEG/ 10 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 090600Z --- 21.1S 167.2E MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING EXTRATROPICAL RADIUS OF 064 KT WINDS - 035 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 035 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 065 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 055 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 160 NM NORTHEAST QUADRANT 180 NM SOUTHEAST QUADRANT 130 NM SOUTHWEST QUADRANT 095 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 140 DEG/ 12 KTS --- 72 HRS, VALID AT: 100600Z --- 24.7S 170.4E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY EXTRATROPICAL RADIUS OF 034 KT WINDS - 135 NM NORTHEAST QUADRANT 180 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT --- REMARKS: 070900Z POSITION NEAR 15.0S 164.7E. TROPICAL CYCLONE (TC) 18P (DONNA), LOCATED APPROXIMATELY 283 NM NORTHWEST OF PORT VILA, VANUATU, HAS TRACKED SOUTH-SOUTHEASTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS IMPROVED CONVECTIVE ORGANIZATION WITH A 17- NM EYE EVIDENT, HOWEVER, DEEP CONVECTION CONTINUES TO CYCLE RAPIDLY. A 070500Z SSMIS 91 GHZ IMAGE SHOWS ASYMMETRIC CORE CONVECTION WITH A DEEP CONVECTIVE BAND OVER THE WESTERN SEMI-CIRCLE AND SHALLOW BANDING OVER THE EASTERN SEMI-CIRCLE OF THE EYEWALL. UPPER-LEVEL ANALYSIS INDICATES CYCLONIC FLOW OVER THE CORE, WHICH IS LIKELY CONTRIBUTING TO THE FLAT TREND AND PULSATING CONVECTION, DIVERGING INTO A STRONG POLEWARD OUTFLOW CHANNEL TO THE SOUTHWEST. THE CURRENT INTENSITY REMAINS ASSESSED AT 85 KNOTS BASED ON AN AVERAGE OF 4.5/5.0 DVORAK ESTIMATES FROM PGTW, KNES AND PHFO. CURRENT MODEL ANALYSES INDICATE THAT THE WESTERN SUBTROPICAL RIDGE (STR) HAS ERODED DUE TO AN APPROACHING MAJOR SHORTWAVE TROUGH, THEREFORE, THE EASTERN STR IS NOW THE DOMINANT STEERING RIDGE. CONSEQUENTLY, TC 18P HAS ACCELERATED SOUTHWARD AS IT TRACKS ALONG THE WESTERN PERIPHERY OF THE STR. TC DONNA SHOULD CONTINUE TO TRACK SOUTHWARD TO SOUTH- SOUTHEASTWARD THROUGH THE FORECAST PERIOD. DYNAMIC GUIDANCE REMAINS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. TC 18P IS FORECAST TO INTENSIFY SLIGHTLY WITHIN THE NEXT 24 HOURS DUE TO WARM SST AND ROBUST POLEWARD OUTFLOW WITH SOME UNCERTAINTY DUE TO THE COMPLEX UPPER-LEVEL FLOW OVER THE CORE. AFTER TAU 24, GRADUAL WEAKENING SHOULD OCCUR AS THE SYSTEM TRACKS OVER MARGINAL SST. BY TAU 48, TC 18P WILL BEGIN EXTRA-TROPICAL TRANSITION AND RAPIDLY WEAKEN AS IT INTERACTS WITH THE MIDLATITUDE WESTERLIES AND THE WEAK BAROCLINIC ZONE. THE SYSTEM IS EXPECTED TO COMPLETE EXTRA-TROPICAL TRANSITION AS IT BECOMES EMBEDDED WITHIN THE MIDLATITUDE WESTERLIES. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 070600Z IS 24 FEET. NEXT WARNINGS AT 071500Z, 072100Z, 080300Z AND 080900Z.//