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Tropical Cyclone ALISTAIR : JTWC Advisories
Season 2000-2001 Summaries (Operational Data): [AU] [SIO] [SPAC] [SH]
---> Tropical Cyclone ALISTAIR Track Map and Data

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.//

Tropical cyclone tracks developed by Michael Bath using operational warnings and advisories.


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Document: tropical_cyclone_alistair_jtwc_advisories.htm Updated: 2 May 2017