Subject: Indian-S: 1. Tropical Cyclone 20s (alistair) Warning Nr 013

From: SIU Weather Processor <[email-masked]>
Date: Thu, 19 Apr 2001 21:03:31 -0500

WTXS31 PGTW 200300
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.//

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