Subject: Indian-S: 1. Tropical Cyclone 20s (alistair) Warning Nr 018

From: SIU Weather Processor <[email-masked]>
Date: Sat, 21 Apr 2001 03:28:55 -0500

WTXS31 PGTW 210900
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.//

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