Subject: Indian-S: 1. Tropical Cyclone 20s (alistair) Warning Nr 012

From: SIU Weather Processor <[email-masked]>
Date: Thu, 19 Apr 2001 15:10:52 -0500

WTXS31 PGTW 192100
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.//

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