Tropical
Cyclones
[Index] |
Tropical Cyclone ALISTAIR [Australian Region][South Indian Ocean][South Pacific Ocean] |
WTPS21 PGTW 20010416 01:00z RMKS/ 1. IMMEDIATE DELIVERY REQ TO AMEMBASSY PORT MORESBY 2. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 160 NM EITHER SIDE OF A LINE FROM 8.1S9 136.8E8 TO 8.8S6 131.1E6 WITHIN THE NEXT 06 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT IMAGERY AT 152330Z4 INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 8.3S1 135.7E6. THE SYSTEM IS MOVING WESTWARD AT 02 KNOTS. 3. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 6.7S3 136.2E2, IN THE ARAFURA SEA, HAS CONTINUED TO ORGANIZE OVER THE PAST 12 HOURS AND IS NOW LOCATED NEAR 8.3S1 135.7E6. RECENT VISIBLE IMAGERY REVEALS BANDS OF STRONG CONVECTION ASSOCIATED WITH THE SYSTEM AND CYCLONIC TURNING. RECENT MICROWAVE AND SCATTEROMETER DATA INDICATE A LOW LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH THE CONVECTION. UW- CIMSS VERTICAL WIND SHEAR PRODUCTS INDICATE THE SYSTEM IS UNDER WEAK TO MODERATE VERTICAL WIND SHEAR AND BENEATH THE UPPER-LEVEL RIDGE AXIS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED AT 1004 MB THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO GOOD. 4. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 170100Z9.// ========================================================================= WTXS31 PGTW 20010416 09:00z IMMEDIATE DELIVERY REQ TO AMEMBASSY PORT MORESBY 1. TROPICAL CYCLONE 20S WARNING NR 001 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 160600Z3 --- NEAR 7.0S7 134.3E1 MOVEMENT PAST SIX HOURS - 270 DEGREES AT 05 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT REPEAT POSIT: 7.0S7 134.3E1 --- FORECASTS: 12 HRS, VALID AT: 161800Z6 --- 7.1S8 133.1E8 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT VECTOR TO 24 HR POSIT: 260 DEG/ 07 KTS --- 24 HRS, VALID AT: 170600Z4 --- 7.3S0 131.8E3 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT VECTOR TO 36 HR POSIT: 260 DEG/ 08 KTS --- 36 HRS, VALID AT: 171800Z7 --- 7.6S3 130.3E7 MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT RADIUS OF 035 KT WINDS - 040 NM SOUTH SEMICIRCLE 035 NM ELSEWHERE VECTOR TO 48 HR POSIT: 260 DEG/ 08 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 180600Z5 --- 7.9S6 128.8E9 MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT RADIUS OF 035 KT WINDS - 040 NM SOUTH SEMICIRCLE 035 NM ELSEWHERE --- REMARKS: 160900Z6 POSITION NEAR 7.0S7 134.0E8. TROPICAL CYCLONE (TC) 20S HAS DEVELOPED OVER THE ARAFURA SEA ALONG A MONSOON TROUGH. TROPICAL CYCLONE 20S HAS TRACKED WESTWARD AT 05 KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 160530Z5 VISIBLE SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 25 TO 35 KNOTS. SATELLITE ANIMATION DEPICTS INCREASING COVERAGE AS OUTFLOW ALOFT HAS IMPROVED OVER THE NORTHWEST QUADRANT. TC 20S SHOULD TRACK WEST-SOUTHWESTWARD WITHIN THE LOW/MID LEVEL TROPICAL EASTERLIES THROUGH THE PERIOD. THE UPPER RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA SHOULD REMAIN QUASI-STATIONARY, THEREFORE, SLOW DEVELOPMENT OF THE SYSTEM IS FORECAST AS LIGHT TO MODERATE UPPER EASTERLIES INHIBIT SIGNIFICANT DEVELOPMENT. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 150600Z2 IS 10 FEET. THIS WARNING SUPERSEDES AND CANCELS REF A, NAVPACMETOCCEN 160051Z APR 01 TROPICAL CYCLONE FORMATION ALERT (WTPS21 PGTW 160100) NEXT WARNINGS AT 162100Z0 (DTG 161951Z3) AND 170900Z7 (DTG 170751Z1).// ========================================================================= WTXS31 PGTW 20010416 21:00z COR SUBJ: TROPICAL CYCLONE WARNING IMMEDIATE DELIVERY REQ TO AMEMBASSY PORT MORESBY 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 002A CORRECTED 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 161800Z6 --- NEAR 9.3S2 132.9E5 MOVEMENT PAST SIX HOURS - 250 DEGREES AT 09 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT REPEAT POSIT: 9.3S2 132.9E5 --- FORECASTS: 12 HRS, VALID AT: 170600Z4 --- 9.7S6 131.0E5 MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT RADIUS OF 035 KT WINDS - 050 NM SOUTH SEMICIRCLE 040 NM ELSEWHERE VECTOR TO 24 HR POSIT: 260 DEG/ 10 KTS --- 24 HRS, VALID AT: 171800Z7 --- 10.0S1 128.9E0 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 065 NM SOUTH SEMICIRCLE 055 NM ELSEWHERE VECTOR TO 36 HR POSIT: 260 DEG/ 10 KTS --- 36 HRS, VALID AT: 180600Z5 --- 10.3S4 126.9E8 MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT RADIUS OF 035 KT WINDS - 085 NM SOUTH SEMICIRCLE 070 NM ELSEWHERE VECTOR TO 48 HR POSIT: 260 DEG/ 10 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 181800Z8 --- 10.6S7 124.9E6 MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT RADIUS OF 050 KT WINDS - 030 NM RADIUS OF 035 KT WINDS - 105 NM SOUTH SEMICIRCLE 085 NM ELSEWHERE OVER WATER --- REMARKS: 162100Z0 POSITION NEAR 9.4S3 132.4E0. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 225 NM NORTH-NORTHEAST OF DARWIN, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 09 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 161730Z8 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 35 KNOTS. SATELLITE ANIMATION DEPICTS IMPROVING ORGANIZATION AND CONVECTION OVER THE PAST 12 HOURS. TC 20S SHOULD TRACK WEST-SOUTHWESTWARD WITHIN THE LOW/MID LEVEL TROPICAL EASTERLIES THROUGH THE PERIOD. THE UPPER RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA SHOULD REMAIN QUASI- STATIONARY, THEREFORE, SLOW DEVELOPMENT OF THE SYSTEM IS FORECAST AS LIGHT TO MODERATE UPPER EASTERLIES INHIBIT SIGNIFICANT DEVELOPMENT. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 161800Z6 IS 12 FEET. NEXT WARNINGS AT 170900Z7 AND 172100Z1. JUSTIFICATION: CORRECT SATELLITE FIX TYPE FROM VISIBLE TO INFRARED.// ========================================================================= WTXS31 PGTW 20010417 09:00z IMMEDIATE DELIVERY REQ TO AMEMBASSY PORT MORESBY 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 003 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 170600Z4 --- NEAR 10.6S7 130.4E8 MOVEMENT PAST SIX HOURS - 250 DEGREES AT 12 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT REPEAT POSIT: 10.6S7 130.4E8 --- FORECASTS: 12 HRS, VALID AT: 171800Z7 --- 11.7S9 128.3E4 MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT RADIUS OF 035 KT WINDS - 050 NM SOUTH SEMICIRCLE 040 NM ELSEWHERE VECTOR TO 24 HR POSIT: 240 DEG/ 12 KTS --- 24 HRS, VALID AT: 180600Z5 --- 12.9S2 126.1E0 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 065 NM SOUTH SEMICIRCLE OVER WATER 055 NM ELSEWHERE VECTOR TO 36 HR POSIT: 250 DEG/ 12 KTS --- 36 HRS, VALID AT: 181800Z8 --- 13.7S1 123.8E4 MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT RADIUS OF 035 KT WINDS - 085 NM SOUTH SEMICIRCLE 070 NM ELSEWHERE VECTOR TO 48 HR POSIT: 255 DEG/ 12 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 190600Z6 --- 14.4S9 121.4E8 MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT RADIUS OF 035 KT WINDS - 085 NM SOUTH SEMICIRCLE 070 NM ELSEWHERE --- REMARKS: 170900Z7 POSITION NEAR 10.9S0 129.9E1. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 115 NM NORTH-NORTHWEST OF DARWIN, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 12 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 170530Z6 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 30 KNOTS AND 45 KNOTS. SATELLITE ANIMATION DEPICTS PULSING CONVECTION OVER THE WESTERN HALF OF A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER. TC 20S WILL TRACK WEST-SOUTHWESTWARD WITHIN THE LOW/MID LEVEL TROPICAL EASTERLIES THROUGH THE PERIOD. THE UPPER LEVEL RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA SHOULD REMAIN QUASI-STATIONARY, THEREFORE, SLOW DEVELOPMENT OF THE SYSTEM IS FORECAST AS LIGHT TO MODERATE UPPER EASTERLIES INHIBIT SIGNIFICANT DEVELOPMENT. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 170600Z4 IS 12 FEET. NEXT WARNINGS AT 172100Z1 AND 180900Z8.// ========================================================================= WTXS31 PGTW 20010417 21:00z COR SUBJ: TROPICAL CYCLONE WARNING IMMEDIATE DELIVERY REQ TO AMEMBASSY PORT MORESBY 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 004A CORRECTED 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 171800Z7 --- NEAR 11.4S6 128.7E8 MOVEMENT PAST SIX HOURS - 245 DEGREES AT 11 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT RADIUS OF 035 KT WINDS - 050 NM SOUTH SEMICIRCLE 040 NM ELSEWHERE REPEAT POSIT: 11.4S6 128.7E8 --- FORECASTS: 12 HRS, VALID AT: 180600Z5 --- 12.3S6 126.6E5 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 060 NM SOUTH SEMICIRCLE 050 NM ELSEWHERE VECTOR TO 24 HR POSIT: 250 DEG/ 13 KTS --- 24 HRS, VALID AT: 181800Z8 --- 13.1S5 124.1E8 MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT RADIUS OF 035 KT WINDS - 080 NM SOUTH SEMICIRCLE 070 NM ELSEWHERE VECTOR TO 36 HR POSIT: 250 DEG/ 14 KTS --- 36 HRS, VALID AT: 190600Z6 --- 14.0S5 121.4E8 MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT RADIUS OF 050 KT WINDS - 035 NM SOUTH SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 100 NM SOUTH SEMICIRCLE 085 NM ELSEWHERE VECTOR TO 48 HR POSIT: 250 DEG/ 14 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 191800Z9 --- 14.9S4 118.6E6 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 045 NM SOUTH SEMICIRCLE 035 NM ELSEWHERE RADIUS OF 035 KT WINDS - 120 NM SOUTH SEMICIRCLE 110 NM ELSEWHERE VECTOR TO 72 HR POSIT: 250 DEG/ 13 KTS --- 72 HRS, VALID AT: 201800Z1 --- 16.7S4 113.5E0 MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT RADIUS OF 050 KT WINDS - 070 NM SOUTH SEMICIRCLE 060 NM ELSEWHERE RADIUS OF 035 KT WINDS - 135 NM SOUTH SEMICIRCLE 125 NM ELSEWHERE --- REMARKS: 172100Z1 POSITION NEAR 11.6S8 128.2E3. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 140 NM WEST-NORTHWEST OF DARWIN, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 11 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 171730Z9 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 35 AND 45 KNOTS. ANIMATED INFRARED IMAGERY DEPICTS DEEP CONVECTION OVER THE APPARENT LOW-LEVEL CIRCULATION CENTER. ANIMATED IMAGERY AND THE 200 MB ANALYSIS INDICATES THE SYSTEM IS EXPERIENCING VERTICAL WIND SHEAR FROM NORTHEASTERLY WINDS EQUATORWARD OF THE UPPER-LEVEL RIDGE AXIS. TC 20S IS FORECAST TO TRACK WEST-SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER AUSTRALIA. THE UPPER RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA IS EXPECTED TO MOVE OVER THE TIMOR SEA AND WILL PROVIDE MORE FAVORABLE OUTFLOW CONDITIONS BY THE END OF THE FORECAST PERIOD. THE OVERALL ENVIRONMENT FOR DEVELOPMENT INDICATES A SLOW INTENSIFICATION THROUGHOUT THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 171800Z7 IS 14 FEET. NEXT WARNINGS AT 180300Z2, 180900Z8, 181500Z5 AND 182100Z2. JUSTIFICATION: CORRECT CHECKSUM IN WARNING POSITION FIX TIME.// ========================================================================= WTXS31 PGTW 20010418 03:00z SUBJ: TROPICAL CYCLONE WARNING 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 005 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 180000Z9 --- NEAR 12.4S7 127.1E1 MOVEMENT PAST SIX HOURS - 235 DEGREES AT 13 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 050 NM SOUTH SEMICIRCLE 040 NM ELSEWHERE REPEAT POSIT: 12.4S7 127.1E1 --- FORECASTS: 12 HRS, VALID AT: 181200Z2 --- 13.6S0 124.6E3 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 065 NM SOUTH SEMICIRCLE 050 NM ELSEWHERE VECTOR TO 24 HR POSIT: 260 DEG/ 11 KTS --- 24 HRS, VALID AT: 190000Z0 --- 13.9S3 122.4E9 MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT RADIUS OF 050 KT WINDS - 035 NM SOUTH SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 080 NM SOUTH SEMICIRCLE 070 NM ELSEWHERE VECTOR TO 36 HR POSIT: 255 DEG/ 11 KTS --- 36 HRS, VALID AT: 191200Z3 --- 14.4S9 120.1E4 MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT RADIUS OF 050 KT WINDS - 035 NM SOUTH SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 100 NM SOUTH SEMICIRCLE 085 NM ELSEWHERE VECTOR TO 48 HR POSIT: 250 DEG/ 14 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 200000Z2 --- 15.4S0 117.3E2 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 045 NM SOUTH SEMICIRCLE 035 NM ELSEWHERE RADIUS OF 035 KT WINDS - 120 NM SOUTH SEMICIRCLE 110 NM ELSEWHERE VECTOR TO 72 HR POSIT: 245 DEG/ 14 KTS --- 72 HRS, VALID AT: 210000Z3 --- 17.6S4 111.9E2 MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT RADIUS OF 050 KT WINDS - 070 NM SOUTH SEMICIRCLE 060 NM ELSEWHERE RADIUS OF 035 KT WINDS - 135 NM SOUTH SEMICIRCLE 125 NM ELSEWHERE --- REMARKS: 180300Z2 POSITION NEAR 12.7S0 126.5E4. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 430 NM NORTHEAST OF BROOME, AUSTRALIA, HAS TRACKED SOUTHWESTWARD AT 13 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 172330Z6 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 45 KNOTS. ANIMATED MULTI-SPECTRAL SATELLITE IMAGERY REVEALS THAT THE DEEP CONVECTION IS RE-ESTABLISHED OVER THE LOW-LEVEL CIRCULATION CENTER. ANIMATED IMAGERY AND THE 200 MB ANALYSIS INDICATE THE SYSTEM CONTINUES TO BE AFFECTED BY NORTHEASTERLY WINDS EQUATORWARD OF THE UPPER-LEVEL RIDGE AXIS. TC 20S IS FORECAST TO TRACK WEST- SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER AUSTRALIA. THE UPPER RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA IS EXPECTED TO MOVE OVER THE TIMOR SEA AND WILL PROVIDE MORE FAVORABLE OUTFLOW CONDITIONS BY THE MID-PERIOD. TC 20S IS EXPECTED TO SLOWLY INTENSIFY THROUGH THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 180000Z9 IS 14 FEET. NEXT WARNINGS AT 180900Z8, 181500Z5, 182100Z2 AND 190300Z3.// ========================================================================= WTXS31 PGTW 20010418 09:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 006 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 180600Z5 --- NEAR 13.5S9 125.7E5 MOVEMENT PAST SIX HOURS - 235 DEGREES AT 18 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT RADIUS OF 050 KT WINDS - 025 NM NORTH SEMICIRCLE 035 NM ELSEWHERE OVER WATER RADIUS OF 035 KT WINDS - 075 NM SOUTH SEMICIRCLE OVER WATER 060 NM ELSEWHERE REPEAT POSIT: 13.5S9 125.7E5 --- FORECASTS: 12 HRS, VALID AT: 181800Z8 --- 14.9S4 123.4E0 MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT RADIUS OF 050 KT WINDS - 035 NM SOUTH SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 075 NM SOUTH SEMICIRCLE OVER WATER 060 NM ELSEWHERE VECTOR TO 24 HR POSIT: 245 DEG/ 13 KTS --- 24 HRS, VALID AT: 190600Z6 --- 16.1S8 120.9E2 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 040 NM SOUTH SEMICIRCLE 030 NM ELSEWHERE RADIUS OF 035 KT WINDS - 085 NM SOUTH SEMICIRCLE 075 NM ELSEWHERE VECTOR TO 36 HR POSIT: 245 DEG/ 13 KTS --- 36 HRS, VALID AT: 191800Z9 --- 17.1S9 118.4E4 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 040 NM SOUTH SEMICIRCLE 030 NM ELSEWHERE RADIUS OF 035 KT WINDS - 090 NM SOUTH SEMICIRCLE 080 NM ELSEWHERE VECTOR TO 48 HR POSIT: 250 DEG/ 13 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 200600Z8 --- 18.1S0 115.8E5 MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT RADIUS OF 050 KT WINDS - 055 NM SOUTH SEMICIRCLE 045 NM ELSEWHERE RADIUS OF 035 KT WINDS - 120 NM SOUTH SEMICIRCLE 105 NM ELSEWHERE VECTOR TO 72 HR POSIT: 255 DEG/ 13 KTS --- 72 HRS, VALID AT: 210600Z9 --- 19.5S5 110.3E5 MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT RADIUS OF 050 KT WINDS - 055 NM SOUTH SEMICIRCLE 045 NM ELSEWHERE RADIUS OF 035 KT WINDS - 120 NM SOUTH SEMICIRCLE 105 NM ELSEWHERE --- REMARKS: 180900Z8 POSITION NEAR 13.8S2 125.1E9. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 200 NM NORTHEAST OF YAMPI SOUND, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 18 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 180530Z7 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 55 KNOTS. ANIMATED MULTI-SPECTRAL SATELLITE IMAGERY REVEALS THAT THE DEEP CONVECTION IS RE-ESTABLISHED OVER THE LOW-LEVEL CIRCULATION CENTER. TC 20S IS FORECAST TO TRACK WEST-SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER AUSTRALIA. THE UPPER RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA IS EXPECTED TO MOVE OVER THE TIMOR SEA AND WILL PROVIDE MORE FAVORABLE OUTFLOW. UNDER THIS MORE FAVORABLE ENVIRONMENT TC 20S IS EXPECTED TO INTENSIFY THROUGH THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 180600Z5 IS 16 FEET. NEXT WARNINGS AT 181500Z5, 182100Z2, 190300Z3, AND 190900Z9.// ========================================================================= WTXS31 PGTW 20010418 15:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 007 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 181200Z2 --- NEAR 14.3S8 124.5E2 MOVEMENT PAST SIX HOURS - 235 DEGREES AT 14 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT RADIUS OF 050 KT WINDS - 035 NM NORTH SEMICIRCLE 045 NM ELSEWHERE RADIUS OF 035 KT WINDS - 095 NM SOUTH SEMICIRCLE OVER WATER 070 NM ELSEWHERE REPEAT POSIT: 14.3S8 124.5E2 --- FORECASTS: 12 HRS, VALID AT: 190000Z0 --- 15.9S5 122.3E8 MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT RADIUS OF 050 KT WINDS - 050 NM SOUTH SEMICIRCLE 040 NM ELSEWHERE RADIUS OF 035 KT WINDS - 115 NM SOUTH SEMICIRCLE OVER WATER 100 NM ELSEWHERE VECTOR TO 24 HR POSIT: 240 DEG/ 13 KTS --- 24 HRS, VALID AT: 191200Z3 --- 17.2S0 119.9E0 MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE 045 NM ELSEWHERE RADIUS OF 035 KT WINDS - 120 NM SOUTH SEMICIRCLE 105 NM ELSEWHERE VECTOR TO 36 HR POSIT: 245 DEG/ 13 KTS --- 36 HRS, VALID AT: 200000Z2 --- 18.3S2 117.4E3 MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE 050 NM ELSEWHERE RADIUS OF 035 KT WINDS - 120 NM SOUTH SEMICIRCLE 105 NM ELSEWHERE VECTOR TO 48 HR POSIT: 245 DEG/ 13 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 201200Z5 --- 19.4S4 114.9E5 MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT RADIUS OF 050 KT WINDS - 065 NM SOUTH SEMICIRCLE 055 NM ELSEWHERE RADIUS OF 035 KT WINDS - 125 NM SOUTH SEMICIRCLE OVER WATER 110 NM ELSEWHERE VECTOR TO 72 HR POSIT: 245 DEG/ 12 KTS --- 72 HRS, VALID AT: 211200Z6 --- 21.3S6 110.1E3 MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE 050 NM ELSEWHERE RADIUS OF 035 KT WINDS - 125 NM SOUTH SEMICIRCLE 110 NM ELSEWHERE --- REMARKS: 181500Z5 POSITION NEAR 14.7S2 124.0E7. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 120 NM NORTHEAST OF YAMPI SOUND, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 14 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 181130Z4 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 55 KNOTS AND 65 KNOTS. ANIMATED SATELLITE IMAGERY REVEALS DEEPENING CONVECTION AND THE DEVELOPMENT A BANDING EYE FEATURE. TC 20S IS FORECAST TO TRACK WEST-SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER AUSTRALIA. THE UPPER RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA IS MOVING OVER THE TIMOR SEA AND WILL PROVIDE FAVORABLE OUTFLOW. UNDER THIS MORE FAVORABLE ENVIRONMENT TC 20S IS EXPECTED TO INTENSIFY THROUGH THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 181200Z2 IS 16 FEET. NEXT WARNINGS AT 182100Z2, 190300Z3, 190900Z9 AND 191500Z6.// ========================================================================= WTXS31 PGTW 20010418 21:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 008 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 181800Z8 --- NEAR 15.0S6 123.2E8 MOVEMENT PAST SIX HOURS - 240 DEGREES AT 14 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT RADIUS OF 050 KT WINDS - 045 NM SOUTH SEMICIRCLE 035 NM ELSEWHERE RADIUS OF 035 KT WINDS - 100 NM SOUTH SEMICIRCLE 085 NM ELSEWHERE REPEAT POSIT: 15.0S6 123.2E8 --- FORECASTS: 12 HRS, VALID AT: 190600Z6 --- 16.3S0 120.8E1 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 050 NM SOUTH SEMICIRCLE 040 NM ELSEWHERE RADIUS OF 035 KT WINDS - 110 NM SOUTH SEMICIRCLE 095 NM ELSEWHERE VECTOR TO 24 HR POSIT: 240 DEG/ 12 KTS --- 24 HRS, VALID AT: 191800Z9 --- 17.4S2 118.6E6 MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE 045 NM ELSEWHERE RADIUS OF 035 KT WINDS - 115 NM SOUTH SEMICIRCLE 100 NM ELSEWHERE VECTOR TO 36 HR POSIT: 245 DEG/ 14 KTS --- 36 HRS, VALID AT: 200600Z8 --- 18.5S4 116.0E8 MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE 050 NM ELSEWHERE RADIUS OF 035 KT WINDS - 120 NM SOUTH SEMICIRCLE 105 NM ELSEWHERE VECTOR TO 48 HR POSIT: 250 DEG/ 13 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 201800Z1 --- 19.4S4 113.4E9 MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT RADIUS OF 050 KT WINDS - 065 NM SOUTH SEMICIRCLE 055 NM ELSEWHERE RADIUS OF 035 KT WINDS - 125 NM SOUTH SEMICIRCLE 110 NM ELSEWHERE VECTOR TO 72 HR POSIT: 215 DEG/ 11 KTS --- 72 HRS, VALID AT: 211800Z2 --- 23.0S5 110.8E0 MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT RADIUS OF 050 KT WINDS - 060 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE RADIUS OF 035 KT WINDS - 125 NM SOUTHEAST SEMICIRCLE 110 NM ELSEWHERE --- REMARKS: 182100Z2 POSITION NEAR 15.3S9 122.6E1. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 70 NM NORTH-NORTHWEST OF YAMPI SOUND, AUSTRALIA, HAS TRACKED WEST- SOUTHWESTWARD AT 14 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 181730Z0 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 55 AND 65 KNOTS. ANIMATED SATELLITE IMAGERY REVEALS STEADY CONVECTION AND AND AN EMBEDDED CENTER. TC 20S IS FORECAST TO TRACK WEST- SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER AUSTRALIA THROUGH 48 HOURS. AFTER THAT, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE AS A MID-LATITUDE TROUGH APPROACHES. THE UPPER RIDGE CURRENTLY SITUATED OVER NORTHERN AUSTRALIA IS MOVING OVER THE TIMOR SEA AND WILL PROVIDE FAVORABLE OUTFLOW. TC 20S IS EXPECTED TO SLOWLY INTENSIFY THROUGH THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 181800Z8 IS 16 FEET. NEXT WARNINGS AT 190300Z3, 190900Z9, 191500Z6 AND 192100Z3.// ========================================================================= WTXS31 PGTW 20010419 03:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 009 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 190000Z0 --- NEAR 15.8S4 122.1E6 MOVEMENT PAST SIX HOURS - 235 DEGREES AT 13 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 045 NM SOUTH SEMICIRCLE 035 NM ELSEWHERE RADIUS OF 035 KT WINDS - 100 NM SOUTH SEMICIRCLE 085 NM ELSEWHERE REPEAT POSIT: 15.8S4 122.1E6 --- FORECASTS: 12 HRS, VALID AT: 191200Z3 --- 17.3S1 120.1E4 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 050 NM SOUTH SEMICIRCLE 040 NM ELSEWHERE RADIUS OF 035 KT WINDS - 110 NM SOUTH SEMICIRCLE 095 NM ELSEWHERE VECTOR TO 24 HR POSIT: 235 DEG/ 15 KTS --- 24 HRS, VALID AT: 200000Z2 --- 19.0S0 117.5E4 MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE 045 NM ELSEWHERE RADIUS OF 035 KT WINDS - 115 NM SOUTH SEMICIRCLE 100 NM ELSEWHERE VECTOR TO 36 HR POSIT: 240 DEG/ 11 KTS --- 36 HRS, VALID AT: 201200Z5 --- 20.1S3 115.5E2 MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE OVER WATER 050 NM ELSEWHERE RADIUS OF 035 KT WINDS - 115 NM SOUTH SEMICIRCLE OVER WATER 100 NM ELSEWHERE VECTOR TO 48 HR POSIT: 235 DEG/ 11 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 210000Z3 --- 21.4S7 113.6E1 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 060 NM SOUTH SEMICIRCLE OVER WATER 050 NM ELSEWHERE RADIUS OF 035 KT WINDS - 110 NM SOUTH SEMICIRCLE OVER WATER 100 NM ELSEWHERE VECTOR TO 72 HR POSIT: 215 DEG/ 10 KTS --- 72 HRS, VALID AT: 220000Z4 --- 24.6S2 111.3E6 MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT RADIUS OF 050 KT WINDS - 060 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE RADIUS OF 035 KT WINDS - 110 NM SOUTHEAST SEMICIRCLE 095 NM ELSEWHERE --- REMARKS: 190300Z3 POSITION NEAR 16.2S9 21.6E0. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 90 NM WEST-NORTHWEST OF YAMPI SOUND, AUSTRALIA, HAS TRACKED SOUTHWESTWARD AT 13 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 182330Z7 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 55 AND 65 KNOTS. ANIMATED SATELLITE IMAGERY REVEALS STEADY CONVECTION AND A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). TC 20S IS FORECAST TO TRACK SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER AUSTRALIA THROUGH 48 HOURS. AFTER THAT, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE AS A MID-LATITUDE TROUGH APPROACHES. TC 20S IS EXPECTED TO SLOWLY INTENSIFY OVER THE NEXT 36 HOURS AS IT TRACKS OVER WARM WATER. AFTER THAT, VERTICAL SHEAR SHOULD SERVE TO WEAKEN THE SYSTEM. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 190000Z0 IS 16 FEET. NEXT WARNINGS AT 190900Z9, 191500Z6, 192100Z3 AND 200300Z5.// ========================================================================= WTXS31 PGTW 20010419 09:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 010 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 190600Z6 --- NEAR 16.8S5 120.9E2 MOVEMENT PAST SIX HOURS - 230 DEGREES AT 15 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 035 NM SOUTHEAST SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 075 NM SOUTHEAST SEMICIRCLE 055 NM ELSEWHERE REPEAT POSIT: 16.8S5 120.9E2 --- FORECASTS: 12 HRS, VALID AT: 191800Z9 --- 18.5S4 118.8E8 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 035 NM SOUTHEAST SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 075 NM SOUTHEAST SEMICIRCLE 055 NM ELSEWHERE VECTOR TO 24 HR POSIT: 225 DEG/ 11 KTS --- 24 HRS, VALID AT: 200600Z8 --- 20.0S2 117.1E0 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 030 NM SOUTHEAST SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE VECTOR TO 36 HR POSIT: 225 DEG/ 09 KTS --- 36 HRS, VALID AT: 201800Z1 --- 21.2S5 115.8E5 MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT RADIUS OF 050 KT WINDS - 025 NM SOUTHEAST SEMICIRCLE OVER WATER 015 NM ELSEWHERE RADIUS OF 035 KT WINDS - 065 NM SOUTHEAST SEMICIRCLE OVER WATER 045 NM ELSEWHERE OVER WATER VECTOR TO 48 HR POSIT: 220 DEG/ 09 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 210600Z9 --- 22.6S0 114.5E1 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 055 NM SOUTHEAST SEMICIRCLE OVER WATER 035 NM ELSEWHERE OVER WATER VECTOR TO 72 HR POSIT: 190 DEG/ 07 KTS --- 72 HRS, VALID AT: 220600Z0 --- 25.2S9 114.1E7 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT --- REMARKS: 190900Z9 POSITION NEAR 17.2S0 120.4E7. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 100 NM NORTHWEST OF BROOME, AUSTRALIA, HAS TRACKED SOUTHWESTWARD AT 15 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 190530Z8 VISIBLE SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 55 AND 65 KNOTS. VISIBLE ANIMATION DEPICTS AN ASYMMETRIC SYSTEM WITH A (APPROX) 110 NM CENTRAL DENSE OVERCAST SITUATED OVER THE VORTEX CENTER. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER AUSTRALIA THROUGH 48 HOURS. AFTERWARD, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD WITH AN APPROACH OF A MID-LATITUDE FROM THE SOUTHWEST. TC 20S HAS BEGUN ITS TRACK POLEWARD OF THE SUBTROPICAL RIDGE AXIS AND BENEATH LIGHT TO MODERATE UPPER WEST-NORTHWESTERLIES. THEREFORE, THE SYSTEM IS FORECAST TO MAINTAIN CURRENT INTENSITY OVER THE NEXT 12 TO 24 HOURS BEFORE SHOWING A SIGNIFICANT WEAKENING TREND THROUGH THE REMAINDER OF THE PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 190600Z6 IS 16 FEET. NEXT WARNINGS AT 191500Z6, 192100Z3, 200300Z5 AND 200900Z1.// ========================================================================= WTXS31 PGTW 20010419 15:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 011 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 191200Z3 --- NEAR 17.5S3 120.3E6 MOVEMENT PAST SIX HOURS - 225 DEGREES AT 10 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT RADIUS OF 050 KT WINDS - 035 NM SOUTHEAST SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 075 NM SOUTHEAST SEMICIRCLE 055 NM ELSEWHERE REPEAT POSIT: 17.5S3 120.3E6 --- FORECASTS: 12 HRS, VALID AT: 200000Z2 --- 18.5S4 118.6E6 MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 050 KT WINDS - 035 NM SOUTHEAST SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 075 NM SOUTHEAST SEMICIRCLE 055 NM ELSEWHERE VECTOR TO 24 HR POSIT: 235 DEG/ 10 KTS --- 24 HRS, VALID AT: 201200Z5 --- 19.6S6 116.8E6 MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 050 KT WINDS - 030 NM SOUTHEAST SEMICIRCLE 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE VECTOR TO 36 HR POSIT: 235 DEG/ 08 KTS --- 36 HRS, VALID AT: 210000Z3 --- 20.6S8 115.4E1 MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 050 KT WINDS - 025 NM SOUTHEAST SEMICIRCLE 015 NM ELSEWHERE RADIUS OF 035 KT WINDS - 065 NM SOUTHEAST SEMICIRCLE OVER WATER 045 NM ELSEWHERE VECTOR TO 48 HR POSIT: 225 DEG/ 08 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 211200Z6 --- 21.7S0 114.2E8 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 035 KT WINDS - 060 NM SOUTHEAST SEMICIRCLE OVER WATER 040 NM ELSEWHERE VECTOR TO 72 HR POSIT: 190 DEG/ 07 KTS --- 72 HRS, VALID AT: 221200Z7 --- 24.5S1 113.6E1 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND --- REMARKS: 191500Z6 POSITION NEAR 17.8S6 119.9E0. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 115 NM WEST-NORTHWEST OF BROOME, AUSTRALIA, HAS TRACKED SOUTHWESTWARD AT 10 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 191130Z5 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 55 AND 65 KNOTS. ENHANCED INFRARED ANIMATION DEPICTS A POORLY DEFINED LOW-LEVEL CIRCULATION CENTER. DIFFLUENCE ALOFT ASSOCIATED WITH THE WESTERN EXTENT OF THE SUBTROPICAL RIDGE HAS HELPED TO GENERATE A NEW BURST OF DEEP CONVECTION OVER THE WESTERN QUADRANT. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER WESTERN AUSTRALIA THROUGH 48 HOURS. AFTERWARD, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD WITH AN APPROACH OF A MID-LATITUDE FROM THE SOUTHWEST. TC 20S HAS BEGUN ITS TRACK POLEWARD OF THE SUBTROPICAL RIDGE AXIS AND INTO A REGION OF LIGHT TO MODERATE UPPER WEST-NORTHWESTERLIES. THEREFORE, THE SYSTEM SHOULD SHOW A WEAKENING TREND THROUGH THE PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 191200Z3 IS 14 FEET. NEXT WARNINGS AT 192100Z3 ,200300Z5, 200900Z1 AND 201500Z8.// ========================================================================= WTXS31 PGTW 20010419 21:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 012 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 191800Z9 --- NEAR 17.4S2 118.8E8 MOVEMENT PAST SIX HOURS - 250 DEGREES AT 10 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT RADIUS OF 050 KT WINDS - 025 NM 025 NM ELSEWHERE RADIUS OF 035 KT WINDS - 080 NM SOUTHEAST SEMICIRCLE 060 NM ELSEWHERE REPEAT POSIT: 17.4S2 118.8E8 --- FORECASTS: 12 HRS, VALID AT: 200600Z8 --- 18.5S4 116.9E7 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 075 NM SOUTHEAST SEMICIRCLE 055 NM ELSEWHERE VECTOR TO 24 HR POSIT: 230 DEG/ 10 KTS --- 24 HRS, VALID AT: 201800Z1 --- 19.7S7 115.3E0 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 210 DEG/ 11 KTS --- 36 HRS, VALID AT: 210600Z9 --- 21.5S8 114.1E7 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 48 HR POSIT: 185 DEG/ 12 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 211800Z2 --- 23.8S3 113.8E3 MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND --- REMARKS: 192100Z3 POSITION NEAR 17.7S5 118.3E3. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 170 NM NORTH OF PORT HEDLAND, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 10 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 191730Z1 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 55 KNOTS. ENHANCED INFRARED ANIMATION DEPICTS A POORLY DEFINED LOW-LEVEL CIRCULATION CENTER WITH CONVECTION SHEARED TOWARDS THE SOUTH. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD OVER THE NEXT 24 HOURS UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER WESTERN AUSTRALIA. AFTERWARD, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD WITH AN APPROACH OF A MID-LATITUDE TROUGH FROM THE SOUTHWEST. TC 20S HAS TRACKED POLEWARD OF THE SUBTROPICAL RIDGE AXIS AND INTO A REGION OF MODERATE UPPER WEST-NORTHWESTERLIES. THEREFORE, THE SYSTEM SHOULD SHOW A WEAKENING TREND THROUGH THE PERIOD, DISSIPATING BY 48 HOURS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 191800Z9 IS 14 FEET. NEXT WARNINGS AT 200300Z5, 200900Z1, 201500Z8 AND 202100Z5.// ========================================================================= WTXS31 PGTW 20010420 03:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 013 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 200000Z2 --- NEAR 17.9S7 116.7E5 MOVEMENT PAST SIX HOURS - 255 DEGREES AT 18 KTS POSITION ACCURATE TO WITHIN 045 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT RADIUS OF 050 KT WINDS - 020 NM SOUTHEAST SEMICIRCLE 020 NM ELSEWHERE RADIUS OF 035 KT WINDS - 080 NM SOUTHEAST SEMICIRCLE 060 NM ELSEWHERE REPEAT POSIT: 17.9S7 116.7E5 --- FORECASTS: 12 HRS, VALID AT: 201200Z5 --- 18.8S7 114.5E1 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 065 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE VECTOR TO 24 HR POSIT: 225 DEG/ 09 KTS --- 24 HRS, VALID AT: 210000Z3 --- 20.1S3 113.1E6 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 210 DEG/ 06 KTS --- 36 HRS, VALID AT: 211200Z6 --- 21.2S5 112.4E8 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 48 HR POSIT: 200 DEG/ 07 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 220000Z4 --- 22.6S0 111.9E2 MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 200300Z5 POSITION NEAR 18.1S0 116.2E0. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 185 NM NORTHWEST OF PORT HEDLAND, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 18 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 192330Z8 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS. MULTI-SPECTRAL SATELLITE IMAGERY DEPICTS A FULLY EXPOSED LOW- LEVEL CIRCULATION CENTER WITH CONVECTION SHEARED TO THE SOUTH. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD OVER THE NEXT 12 HOURS UNDER THE STEERING INFLUENCE OF THE MID-LEVEL RIDGE ESTABLISHED OVER WESTERN AUSTRALIA. AFTERWARD, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD WITH AN APPROACH OF A MID-LATITUDE TROUGH FROM THE SOUTHWEST. TC 20S HAS TRACKED POLEWARD OF THE SUBTROPICAL RIDGE AXIS AND INTO A REGION OF MODERATE TO STRONG UPPER WEST-NORTHWESTERLIES. THEREFORE, THE SYSTEM WILL SHOW A WEAKENING TREND THROUGH THE PERIOD, DISSIPATING BY 48 HOURS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 200000Z2 IS 12 FEET. NEXT WARNINGS AT 200900Z1, 201500Z8, 202100Z5 AND 210300Z6.// ========================================================================= WTXS31 PGTW 20010420 09:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 014 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 200600Z8 --- NEAR 18.4S3 114.8E4 MOVEMENT PAST SIX HOURS - 255 DEGREES AT 16 KTS POSITION ACCURATE TO WITHIN 040 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE REPEAT POSIT: 18.4S3 114.8E4 --- FORECASTS: 12 HRS, VALID AT: 201800Z1 --- 19.6S6 113.0E5 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 24 HR POSIT: 235 DEG/ 10 KTS --- 24 HRS, VALID AT: 210600Z9 --- 20.7S9 111.2E5 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 205 DEG/ 07 KTS --- 36 HRS, VALID AT: 211800Z2 --- 22.0S4 110.5E7 MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 200900Z1 POSITION NEAR 18.7S6 114.3E9. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 235 NM NORTH OF LEARMONTH, AUSTRALIA, HAS TRACKED WEST-SOUTHWESTWARD AT 16 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 200530Z0 VISIBLE SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 45 KNOTS. MULTI-SPECTRAL SATELLITE IMAGERY DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER WITH ASSOCIATED WEAKENING CONVECTION DECOUPLED ABOUT 36 NM TO THE SOUTH THROUGH SOUTHEAST. TC 20S IS FORECAST TO TRACK INCREASINGLY SOUTHWESTWARD OVER THE NEXT 24 HOURS. AFTERWARD, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD WITH A WEAKNESS IN THE LOW/MID LEVEL RIDGE. TC 20S IS FORECAST TO DISSIPATE BY THE END OF THE PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 200600Z8 IS 12 FEET. NEXT WARNINGS AT 201500Z8, 202100Z5, 210300Z6 AND 210900Z2.// ========================================================================= WTXS31 PGTW 20010420 15:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 015 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 201200Z5 --- NEAR 18.6S5 113.8E3 MOVEMENT PAST SIX HOURS - 260 DEGREES AT 10 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE REPEAT POSIT: 18.6S5 113.8E3 --- FORECASTS: 12 HRS, VALID AT: 210000Z3 --- 19.4S4 112.0E4 MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 035 KT WINDS - 080 NM SOUTHEAST SEMICIRCLE 035 NM ELSEWHERE VECTOR TO 24 HR POSIT: 225 DEG/ 10 KTS --- 24 HRS, VALID AT: 211200Z6 --- 20.7S9 110.5E7 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 205 DEG/ 07 KTS --- 36 HRS, VALID AT: 220000Z4 --- 21.9S2 109.9E9 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 48 HR POSIT: 180 DEG/ 08 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 221200Z7 --- 23.5S0 109.9E9 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 201500Z8 POSITION NEAR 18.8S7 113.3E8. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 215 NM NORTH OF LEARMONTH, AUSTRALIA, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 201130Z7 ENHANCED INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 35 TO 55 KNOTS. ENHANCED INFRARED ANIMATION DEPICTS THAT THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS TUCKED BENEATH THE WESTERN EDGE OF THE CONVECTION DURING THE PAST 6 HOURS. A 200954Z0 TROPICAL RAINFALL MEASURING MISSION (TRMM 37 GHZ) PASS DEPICTED A DEFINED LLCC WITH A BANDING FEATURE SITUATED OVER THE SOUTHEAST QUADRANT. TC 20S IS FORECAST TO TRACK INCREASINGLY SOUTHWESTWARD OVER THE NEXT 24 HOURS. AFTERWARD, THE SYSTEM SHOULD BEGIN TO TRACK MORE SOUTHWARD WITH A WEAKNESS IN THE LOW/MID LEVEL RIDGE. TC 20S IS FORECAST TO DISSIPATE BY THE END OF THE PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 201200Z5 IS 12 FEET. NEXT WARNINGS AT 202100Z5, 210300Z6, 210900Z2 AND 211500Z9 .// ========================================================================= WTXS31 PGTW 20010420 21:00z SUBJ: TROPICAL CYCLONE WARNING 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 016 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 201800Z1 --- NEAR 19.4S4 112.6E0 MOVEMENT PAST SIX HOURS - 235 DEGREES AT 14 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE REPEAT POSIT: 19.4S4 112.6E0 --- FORECASTS: 12 HRS, VALID AT: 210600Z9 --- 20.8S0 111.3E6 MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT RADIUS OF 035 KT WINDS - 080 NM SOUTHEAST SEMICIRCLE 035 NM ELSEWHERE VECTOR TO 24 HR POSIT: 205 DEG/ 08 KTS --- 24 HRS, VALID AT: 211800Z2 --- 22.2S6 110.6E8 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 170 DEG/ 08 KTS --- 36 HRS, VALID AT: 220600Z0 --- 23.8S3 110.9E1 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 202100Z5 POSITION NEAR 19.7S7 112.3E7. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 180 NM NORTH-NORTHWEST OF LEARMONTH, AUSTRALIA, HAS TRACKED SOUTHWESTWARD AT 14 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 201730Z3 ENHANCED INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 35 TO 55 KNOTS. ENHANCED INFRARED ANIMATION DEPICTS AN INCREASE IN DEEP CONVECTION OVER THE THE LOW-LEVEL CIRCULATION CENTER (LLCC) OVER THE PAST 6 HOURS. THE SYSTEM CONTINUES TO ENCOUNTER STRONG VERTICAL WIND SHEAR ASSOCIATED WITH UPPER LEVEL WESTERLIES. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD OVER THE NEXT 24 HOURS. AFTERWARD, THE SYSTEM IS EXPECTED TO TRACK SOUTHWARD THROUGH A WEAKNESS IN THE LOW/MID LEVEL RIDGE CREATED BY AN APPROACHING TROUGH. TC 20S IS FORECAST TO CONTINUE WEAKENING IN INCREASING VERTICAL WIND SHEAR AND DISSIPATE AS A SIGNIFICANT TROPICAL CYCLONE BY THE END OF THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 201800Z1 IS 12 FEET. NEXT WARNINGS AT 210300Z6, 210900Z2, 211500Z9 AND 212100Z6.// ========================================================================= WTXS31 PGTW 20010421 03:00Z SUBJ: TROPICAL CYCLONE WARNING 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 017 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 210000Z3 --- NEAR 20.1S3 111.9E2 MOVEMENT PAST SIX HOURS - 225 DEGREES AT 11 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 DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 035 KT WINDS - 080 NM SOUTHEAST SEMICIRCLE 050 NM ELSEWHERE REPEAT POSIT: 20.1S3 111.9E2 --- FORECASTS: 12 HRS, VALID AT: 211200Z6 --- 21.7S0 110.7E9 MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 24 HR POSIT: 200 DEG/ 07 KTS --- 24 HRS, VALID AT: 220000Z4 --- 23.1S6 110.2E4 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 165 DEG/ 10 KTS --- 36 HRS, VALID AT: 221200Z7 --- 25.0S7 110.8E0 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 210300Z6 POSITION NEAR 20.5S7 111.6E9. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 180 NM NORTHWEST OF LEARMONTH, AUSTRALIA, HAS TRACKED SOUTHWESTWARD AT 11 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 202330Z0 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 35 AND 45 KNOTS. RECENT ANIMATED INFRARED ANIMATION REVEALED AN EXPOSED LOW- LEVEL CIRCULATION CENTER (LLCC) 30 NM WEST OF THE DEEP CONVECTION. THE SYSTEM CONTINUES TO ENCOUNTER STRONG VERTICAL WIND SHEAR ASSOCIATED WITH UPPER LEVEL WESTERLIES. A 201759Z4 TROPICAL RAINFALL MEASURING MISSION PASS SUPPORTS THESE FINDINGS. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD OVER THE NEXT 24 HOURS. AFTERWARD, THE SYSTEM IS EXPECTED TO TRACK SOUTHWARD THROUGH A WEAKNESS IN THE LOW/MID LEVEL RIDGE CREATED BY AN APPROACHING TROUGH. TC 20S IS FORECAST TO CONTINUE WEAKENING IN INCREASING VERTICAL WIND SHEAR AND DISSIPATE AS A SIGNIFICANT TROPICAL CYCLONE BY THE END OF THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 210000Z3 IS 12 FEET. NEXT WARNINGS AT 210900Z2, 211500Z9, 212100Z6 AND 220300Z7.// ========================================================================= WTXS31 PGTW 20010421 09:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 018 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 210600Z9 --- NEAR 20.5S7 110.7E9 MOVEMENT PAST SIX HOURS - 250 DEGREES AT 12 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER REPEAT POSIT: 20.5S7 110.7E9 --- FORECASTS: 12 HRS, VALID AT: 211800Z2 --- 21.7S0 109.0E0 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 24 HR POSIT: 195 DEG/ 09 KTS --- 24 HRS, VALID AT: 220600Z0 --- 23.5S0 108.4E3 MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 160 DEG/ 10 KTS --- 36 HRS, VALID AT: 221800Z3 --- 25.4S1 109.1E1 MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 210900Z2 POSITION NEAR 20.8S0 110.3E5. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 215 NM WEST-NORTHWEST OF LEARMONTH, AUSTRALIA, HAS TRACKED WEST- SOUTHWESTWARD AT 12 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 210530Z1 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 35 KNOTS. RECENT ANIMATED INFRARED ANIMATION REVEALED A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) 38 NM WEST OF THE CONVECTION. THE SYSTEM CONTINUES TO ENCOUNTER STRONG VERTICAL WIND SHEAR ASSOCIATED WITH UPPER LEVEL WESTERLIES. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD OVER THE NEXT 24 HOURS. AFTERWARD, THE SYSTEM IS EXPECTED TO TRACK SOUTHWESTWARD THROUGH A WEAKNESS IN THE LOW/MID LEVEL RIDGE CREATED BY AN APPROACHING TROUGH. TC 20S IS FORECAST TO CONTINUE WEAKENING IN AN INCREASING VERTICAL WIND SHEAR ENVIRONMENT AND DISSIPATE BY THE END OF THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 210600Z9 IS 12 FEET. NEXT WARNINGS AT 211500Z9, 212100Z6, 220300Z7, AND 220900Z3.// ========================================================================= WTXS31 PGTW 20010421 15:00z 1. TROPICAL CYCLONE 20S (ALISTAIR) WARNING NR 019 01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 211200Z6 --- NEAR 21.1S4 110.0E2 MOVEMENT PAST SIX HOURS - 225 DEGREES AT 09 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER REPEAT POSIT: 21.1S4 110.0E2 --- FORECASTS: 12 HRS, VALID AT: 220000Z4 --- 22.7S1 108.6E5 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 24 HR POSIT: 180 DEG/ 12 KTS --- 24 HRS, VALID AT: 221200Z7 --- 25.1S8 108.7E6 MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 211500Z9 POSITION NEAR 21.5S8 109.6E6. TROPICAL CYCLONE (TC) 20S (ALISTAIR), LOCATED APPROXIMATELY 240 NM WEST-NORTHWEST OF LEARMONTH, AUSTRALIA, HAS TRACKED SOUTHWESTWARD AT 09 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 211130Z8 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT INTENSITY ESTIMATES OF 35 KNOTS. RECENT ANIMATED INFRARED ANIMATION REVEALED A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) 58 NM WEST OF THE CONVECTION. THE SYSTEM CONTINUES TO ENCOUNTER STRONG VERTICAL WIND SHEAR ASSOCIATED WITH UPPER LEVEL WESTERLIES. TC 20S IS FORECAST TO TRACK SOUTHWESTWARD OVER THE NEXT 24 HOURS AND DISSIPATE BY THE END OF THE FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 211200Z6 IS 12 FEET. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WARNING CENTER (NAVPACMETOCCEN). THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF REGENERATION.//
Document: alistair.htm
Updated: 14th April, 2004 |
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