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Tropical Cyclone ALISON : JTWC Advisories
Season 1998-1999 Summaries (Operational Data): [AU] [SIO] [SPAC] [SH]
---> Tropical Cyclone ALISON Track Map and Data

WTXS31 PGTW 981108 15:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 001
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   081200Z1 --- 11.8S0 98.2E9
     MOVEMENT PAST SIX HOURS - 240 DEGREES AT 06 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: 11.8S0 98.2E9
    ---
   FORECASTS:
   12 HRS, VALID AT:
   090000Z9 --- 12.2S5 97.4E0
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 050 NM SOUTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 235 DEG/ 05 KTS
    ---
   24 HRS, VALID AT:
   091200Z2 --- 12.7S0 96.6E1
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 020 NM SOUTHEAST SEMICIRCLE
                            015 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE
                            065 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 240 DEG/ 06 KTS
    ---
   36 HRS, VALID AT:
   100000Z1 --- 13.3S7 95.6E0
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   RADIUS OF 050 KT WINDS - 040 NM SOUTHEAST SEMICIRCLE
                            035 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 090 NM SOUTHEAST SEMICIRCLE
                            080 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 240 DEG/ 06 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   101200Z4 --- 13.9S3 94.6E9
   MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT
   RADIUS OF 050 KT WINDS - 055 NM SOUTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 110 NM SOUTHEAST SEMICIRCLE
                            100 NM ELSEWHERE
    ---
REMARKS:
081500Z4 POSITION 11.9S1   98.0E7.
TROPICAL CYCLONE 04S (ALISON) HAS FORMED IN THE SOUTHERN INDIAN
OCEAN AND IS MOVING WEST-SOUTHWESTWARD AT 6 KNOTS. THE WARNING
POSITION IS BASED ON 081130Z3 INFRARED SATELLITE IMAGERY. THE
WARNING INTENSITY IS BASED ON 081130Z3 SATELLITE INTENSITY
ESTIMATES OF 35 KNOTS. TROPICAL CYCLONE 04S (ALISON) IS TRACKING
WEST-SOUTHWESTWARD UNDER THE STEERING FLOW FROM THE SUBTROPICAL
RIDGE TO ITS SOUTH. THIS STEERING SHOULD CONTINUE THROUGHOUT THE
FORECAST PERIOD. TROPICAL CYCLONE 04S (ALISON) IS FORECAST TO
INTENSIFY CLIMATOLOGICALLY AT ONE DVORAK T-NUMBER PER DAY AS IT
WILL REMAIN IN AN ENVIRONMENT FAVORABLE FOR INTENSIFICATION. WIND
RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE-SIZED TROPICAL
CYCLONE. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 081200Z1 IS 12 FEET.
NEXT WARNINGS AT 090300Z2 (DTG 090151Z6) AND 091500Z5 (DTG
091351Z9). THIS WARNING SUPERSEDES AND CANCELS NAVPACMETOCCEN WEST
GU 080948Z NOVEMBER 98 TROPICAL CYCLONE FORMATION ALERT (WTXS21 PGTW
080600).//
=========================================================================
WTXS31 PGTW 981108 21:00z
SUBJ:  TROPICAL CYCLONE WARNING
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 002
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   081800Z7 --- 13.1S5 97.3E9
     MOVEMENT PAST SIX HOURS - 225 DEGREES AT 11 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 - 020 NM SOUTHEAST SEMICIRCLE
                            015 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE
                            065 NM ELSEWHERE
   REPEAT POSIT: 13.1S5 97.3E9
    ---
   FORECASTS:
   12 HRS, VALID AT:
   090600Z5 --- 14.2S7 96.0E5
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   RADIUS OF 050 KT WINDS - 040 NM SOUTHEAST SEMICIRCLE
                            030 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 090 NM SOUTHEAST SEMICIRCLE
                            080 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 225 DEG/ 08 KTS
    ---
   24 HRS, VALID AT:
   091800Z8 --- 15.3S9 94.8E1
   MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT
   RADIUS OF 050 KT WINDS - 055 NM SOUTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 110 NM SOUTHEAST SEMICIRCLE
                            100 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 225 DEG/ 08 KTS
    ---
   36 HRS, VALID AT:
   100600Z7 --- 16.4S1 93.6E8
   MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
   RADIUS OF 050 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 135 NM SOUTHEAST SEMICIRCLE
                            125 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 225 DEG/ 08 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   101800Z0 --- 17.5S3 92.4E5
   MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT
   RADIUS OF 050 KT WINDS - 080 NM SOUTHEAST SEMICIRCLE
                            070 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 145 NM SOUTHEAST SEMICIRCLE
                            135 NM ELSEWHERE
    ---
REMARKS:
082100Z1 POSITION 13.4S8   97.0E6.
TROPICAL CYCLONE 04S (ALISON) HAS TRACKED SOUTHWESTWARD AT 11
KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
081730Z9 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY
IS BASED ON A 081730Z9 SATELLITE INTENSITY ESTIMATE OF 55 KNOTS
FROM PGTW. TROPICAL CYCLONE 04S (ALISON) HAS RAPIDLY INTENSIFIED
OVER THE PAST 6 HOURS. 081730Z9 INFRARED IMAGERY SHOWS CONTINUED
CLOUD TOP COOLING AND IMPROVED ORGANIZATION WITH A SUGGESTION
OF THE DEVELOPMENT OF A WARM SPOT INDICATIVE OF A 55 KNOT SYSTEM.
081800Z7 OBSERVATION FROM COCOS ISLAND (WMO 96996) SHOW SUSTAINED
34 KNOTS (TEN-MINUTE AVERAGE) WINDS WITH GUSTS TO 47 KNOTS (TEN-
MINUTE AVERAGE). TROPICAL CYCLONE 04S (ALISON) HAS BEEN
MOVING SOUTHWESTWARD UNDER THE STEERING FLOW FROM THE SUBTROPICAL
RIDGE TO ITS SOUTH. THIS SHOULD REMAIN THE DOMINANT STEERING
THROUGHOUT THE FORECAST PERIOD. HOWEVER, AN APPROACHING MID-LATITUDE
TROUGH MAY WEAKEN THE SUBTROPICAL RIDGE SUFFICIENTLY TO IMPART A
MORE SOUTHWARD COMPONENT TO THE TRACK AFTER THE 36-HOUR FORECAST
POSITION. TROPICAL CYCLONE 04S (ALISON) IS FORECAST TO CONTINUE TO
INTENSIFY THROUGHOUT THE FORECAST PERIOD AS IT SHOULD REMAIN IN AN
ENVIRONMENT FAVORABLE FOR CONTINUED INTENSIFICATION.  WIND RADII
HAVE BEEN ADJUSTED BASED ON SURFACE SYNOPTIC DATA. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 081800Z IS 16 FEET. NEXT WARNINGS AT
090300Z2 (DTG 090151Z6) AND 091500Z5 (DTG 091351Z9).//
=========================================================================
WTXS31 PGTW 981109 03:00z
SUBJ:  TROPICAL CYCLONE WARNING
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 003
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   090000Z9 --- 13.5S9 96.8E3
     MOVEMENT PAST SIX HOURS - 230 DEGREES AT 06 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 SOUTHEAST SEMICIRCLE
                            020 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            090 NM ELSEWHERE OVER WATER
   REPEAT POSIT: 13.5S9 96.8E3
    ---
   FORECASTS:
   12 HRS, VALID AT:
   091200Z2 --- 14.1S6 95.4E8
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   RADIUS OF 050 KT WINDS - 040 NM SOUTHEAST SEMICIRCLE
                            030 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 105 NM SOUTHEAST SEMICIRCLE
                            095 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 245 DEG/ 08 KTS
    ---
   24 HRS, VALID AT:
   100000Z1 --- 14.7S2 93.9E1
   MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT
   RADIUS OF 050 KT WINDS - 055 NM SOUTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 110 NM SOUTHEAST SEMICIRCLE
                            100 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 245 DEG/ 07 KTS
    ---
   36 HRS, VALID AT:
   101200Z4 --- 15.3S9 92.6E7
   MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
   RADIUS OF 050 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 135 NM SOUTHEAST SEMICIRCLE
                            125 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 250 DEG/ 07 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   110000Z2 --- 15.8S4 91.2E2
   MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT
   RADIUS OF 050 KT WINDS - 080 NM SOUTHEAST SEMICIRCLE
                            070 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 145 NM SOUTHEAST SEMICIRCLE
                            135 NM ELSEWHERE
    ---
REMARKS:
090300Z2 POSITION 13.7S1 96.4E9.
TROPICAL CYCLONE (TC) 04S (ALISON) HAS TRACKED SOUTHWESTWARD
JUST SOUTH OF COCOS ISLAND AT 6 KNOTS OVER THE PAST 6 HOURS.
THE WARNING POSITION IS BASED UPON ANIMATED INFRARED SATELLITE
IMAGERY AND A 082330Z6 VISIBLE SATELLITE IMAGE. THE WARNING
INTENSITY IS BASED UPON SATELLITE INTENSITY ESTIMATES OF 55 KNOTS.
TROPICAL CYCLONE 04S (ALISON) IS TRACKING SOUTHWESTWARD UNDER
THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO ITS SOUTH.
ALTHOUGH THE FORECAST PHILOSOPHY REMAINS BASICALLY THE SAME FOR
TC 04S (ALISON), THE FORECAST TRACK WAS SHIFTED SLIGHTLY WESTWARD
AND SLOWED DUE TO THE SHIFTING INFLUENCE OF THE AFOREMENTIONED
SUBTROPICAL RIDGE. TROPICAL CYCLONE 04S (ALISON) SHOULD CONTINUE TO
INTENSIFY THROUGHOUT THE FORECAST PERIOD AS THE UPPER LEVEL
ENVIRONMENT REMAINS FAVORABLE FOR FUTHER DEVELOPMENT. THE WIND
RADII ARE BASED UPON CLIMATOLOGY FOR AN AVERAGE-SIZED TROPICAL
CYCLONE AND HAVE BEEN ADJUSTED IN ACCORDANCE WITH SURFACE SYNOPTIC
DATA FROM COCOS ISLAND. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 090000Z9
IS 14 FEET. NEXT WARNINGS AT 091500Z5 (DTG 091351Z9) AND 100300Z4
(DTG 100151Z8).//
=========================================================================
WTXS31 PGTW 981109 15:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 004
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   091200Z2 --- 13.8S2 095.6E0
     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 - 070 KT, GUSTS 085 KT
   RADIUS OF 050 KT WINDS - 045 NM SOUTHEAST SEMICIRCLE
                            035 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE
                            090 NM ELSEWHERE
   REPEAT POSIT: 13.8S2 095.6E0
    ---
   FORECASTS:
   12 HRS, VALID AT:
   100000Z1 --- 14.2S7 094.3E6
   MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT
   RADIUS OF 050 KT WINDS - 050 NM SOUTHEAST SEMICIRCLE
                            040 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 105 NM SOUTHEAST SEMICIRCLE
                            095 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 250 DEG/ 07 KTS
    ---
   24 HRS, VALID AT:
   101200Z4 --- 14.6S1 093.0E2
   MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
   RADIUS OF 050 KT WINDS - 055 NM SOUTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 110 NM SOUTHEAST SEMICIRCLE
                            100 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 250 DEG/ 07 KTS
    ---
   36 HRS, VALID AT:
   110000Z2 --- 15.1S7 091.7E7
   MAX SUSTAINED WINDS - 095 KT, GUSTS 115 KT
   RADIUS OF 050 KT WINDS - 060 NM SOUTHEAST SEMICIRCLE
                            050 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 120 NM SOUTHEAST SEMICIRCLE
                            110 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 245 DEG/ 06 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   111200Z5 --- 15.6S2 090.5E4
   MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT
   RADIUS OF 050 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 130 NM SOUTHEAST SEMICIRCLE
                            120 NM ELSEWHERE
    ---
REMARKS:
091500Z5 POSITION 13.9S3  095.3E7.
TROPICAL CYCLONE 04S (ALISON) HAS TRACKED WEST-SOUTHWESTWARD AT 9
KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
091142Z7 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY OF 70
KNOTS IS BASED ON 091130Z4 SATELLITE INTENSITY ESTIMATES OF 65 AND
75 KNOTS. TROPICAL CYCLONE 04S (ALISON) CONTINUES TO INTENSIFY AND
IS MOVING WEST-SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE
SUBTROPICAL RIDGE TO ITS SOUTHWEST. ANIMATED WATER VAPOR IMAGERY
SHOWS THIS RIDGE IS REBUILDING AND HAS DEVELOPED A NORTHWEST-
SOUTHEAST ORIENTATION. THE STEERING FLOW FROM THIS RIDGE SHOULD KEEP
TROPICAL CYCLONE 04S (ALISON) MOVING WEST-SOUTHWESTWARD THROUGHOUT
THE FORECAST PERIOD. TROPICAL CYCLONE 04S (ALISON) IS FORECAST TO
CONTINUE TO INTENSIFY THROUGHOUT THE FORECAST PERIOD. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 091200Z2 IS 16 FEET. NEXT WARNINGS AT
100300Z4 (DTG 100151Z8) AND 101500Z7 (DTG 101351Z1).//
=========================================================================
WTXS31 PGTW 981110 03:00z    
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 005    
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   100000Z1 --- NEAR 14.7S2 93.8E0
     MOVEMENT PAST SIX HOURS - 235 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT
   RADIUS OF 050 KT WINDS - 045 NM SOUTHEAST SEMICIRCLE  
                            035 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE  
                            090 NM ELSEWHERE
   REPEAT POSIT: 14.7S2 93.8E0
    ---
   FORECASTS:
   12 HRS, VALID AT:
   101200Z4 --- 15.3S9 92.5E6
   MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT
   RADIUS OF 050 KT WINDS - 050 NM SOUTHEAST SEMICIRCLE  
                            040 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 105 NM SOUTHEAST SEMICIRCLE  
                            095 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 250 DEG/ 07 KTS
    ---
   24 HRS, VALID AT:
   110000Z2 --- 15.7S3 91.2E2
   MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT
   RADIUS OF 050 KT WINDS - 055 NM SOUTHEAST SEMICIRCLE  
                            045 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 110 NM SOUTHEAST SEMICIRCLE  
                            100 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 255 DEG/ 07 KTS
    ---
   36 HRS, VALID AT:
   111200Z5 --- 16.0S7 89.8E5
   MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT
   RADIUS OF 050 KT WINDS - 060 NM SOUTHEAST SEMICIRCLE  
                            050 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 120 NM SOUTHEAST SEMICIRCLE  
                            110 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 250 DEG/ 07 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   120000Z3 --- 16.4S1 88.5E1
   MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
   RADIUS OF 050 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE  
                            060 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 130 NM SOUTHEAST SEMICIRCLE  
                            120 NM ELSEWHERE
    ---
REMARKS:
100300Z4 POSITION NEAR 14.9S4 93.5E7.
ANIMATED INFRARED SATELLITE IMAGERY SHOWS TROPICAL CYCLONE 04S 
(ALISON) HAS CONTINUED TRACKING TOWARDS THE SOUTHWEST AT 8 KNOTS. 
THE WARNING POSITION IS BASED ON 092330Z7 INFRARED SATELLITE 
IMAGERY AND ANIMATION. THE WARNING INTENSITY IS BASED ON A 
COMBINATION OF SATELLITE DERIVED INTENSITY ESTIMATES BETWEEN 65 AND 
77 KNOTS. THE FORECAST PHILOSOPHY REMAINS SIMILAR AS TC 04S IS 
EXPECTED TO CONTINUE GENERALLY TOWARDS THE SOUTHWEST UNDER THE 
INFLUENCE OF THE SUBTROPICAL RIDGE. THROUGH THE 12 HOUR PERIOD, TC 
04S IS EXPECTED TO MAINTAIN ITS CURRENT INTENSITY AS IT IS 
INFLUENCED BY A PASSING MID-LATITUDE TROUGH. AFTERWARDS, TC 04S IS 
EXPECTED TO INTENSIFY SLOWLY THROUGH THE REMAINDER OF THE FORECAST 
PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 100000Z IS 16 FEET. NEXT 
WARNINGS AT 101500Z7 (DTG 101351Z1) AND 110300Z5 (DTG 110151Z9).//
=========================================================================
WTXS31 PGTW 981110 15:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 006
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   101200Z4 --- NEAR 16.3S0 92.8E9
     MOVEMENT PAST SIX HOURS - 215 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT
   RADIUS OF 050 KT WINDS - 045 NM SOUTHEAST SEMICIRCLE
                            035 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE
                            090 NM ELSEWHERE
   REPEAT POSIT: 16.3S0 92.8E9
    ---
   FORECASTS:
   12 HRS, VALID AT:
   110000Z2 --- 17.6S4 91.9E9
   MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT
   RADIUS OF 050 KT WINDS - 050 NM SOUTHEAST SEMICIRCLE
                            040 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 105 NM SOUTHEAST SEMICIRCLE
                            095 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 205 DEG/ 08 KTS
    ---
   24 HRS, VALID AT:
   111200Z5 --- 19.0S0 91.2E2
   MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT
   RADIUS OF 050 KT WINDS - 055 NM SOUTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 110 NM SOUTHEAST SEMICIRCLE
                            100 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 185 DEG/ 08 KTS
    ---
   36 HRS, VALID AT:
   120000Z3 --- 20.5S7 91.0E0
   MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT
   RADIUS OF 050 KT WINDS - 060 NM SOUTHEAST SEMICIRCLE
                            050 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 120 NM SOUTHEAST SEMICIRCLE
                            110 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 175 DEG/ 09 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   121200Z6 --- 22.3S7 91.2E2
   MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
   RADIUS OF 050 KT WINDS - 070 NM SOUTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 130 NM SOUTHEAST SEMICIRCLE
                            120 NM ELSEWHERE
    ---
REMARKS:
101500Z7 POSITION NEAR 16.6S3 92.6E7.
TROPICAL CYCLONE 04S (ALISON) HAS TRACKED TOWARDS THE SOUTHWEST AT
8 KNOTS FOR THE PAST 12 HOURS. THE WARNING POSITION AND INTENSITY
ARE BASED ON 101130Z6 INFRARED SATELLITE IMAGERY AND ANIMATION. THE
TRACK WAS CONFIRMED BY 100343Z1 SCATTEROMETRY DATA. TC 04S IS
EXPECTED TO CONTINUE TOWARDS THE SOUTHWEST UNDER THE INFLUENCE OF
THE SUBTROPICAL RIDGE. THROUGH THE 12-HOUR PERIOD, TC 04S IS
EXPECTED TO MAINTAIN ITS CURRENT INTENSITY AS IT IS INFLUENCED BY A
PASSING MID-LATITUDE TROUGH. BY THE 36-HOUR POINT, THE PASSING
TROUGH IS EXPECTED TO CAUSE A SOUTHWARD TURN IN THE FORECAST TRACK.
TC 04S IS EXPECTED TO INTENSIFY SLOWLY THROUGH THE REMAINDER OF THE
FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 101200Z4 IS 16
FEET. REFER TO WWIO31 PGFW FOR ADDITIONAL SEA HEIGHT INFORMATION.
NEXT WARNINGS AT 110300Z5 (DTG 110151Z9) AND 111500Z8 (DTG
111351Z2).
=========================================================================
WTXS31 PGTW 981111 03:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 007
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   110000Z2 --- NEAR 17.5S3 92.4E5
     MOVEMENT PAST SIX HOURS - 180 DEGREES AT 06 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 - 020 NM
   RADIUS OF 035 KT WINDS - 075 NM EAST SEMICIRCLE
                            065 NM ELSEWHERE
   REPEAT POSIT: 17.5S3 92.4E5
    ---
   FORECASTS:
   12 HRS, VALID AT:
   111200Z5 --- 18.5S4 92.3E4
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   RADIUS OF 050 KT WINDS - 015 NM
   RADIUS OF 035 KT WINDS - 075 NM EAST SEMICIRCLE
                            065 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 180 DEG/ 04 KTS
    ---
   24 HRS, VALID AT:
   120000Z3 --- 19.4S4 92.3E4
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 065 NM SOUTHEAST SEMICIRCLE
                            055 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 180 DEG/ 04 KTS
    ---
   36 HRS, VALID AT:
   121200Z6 --- 20.1S3 92.3E4
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   RADIUS OF 035 KT WINDS - 060 NM EAST SEMICIRCLE
                            050 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 180 DEG/ 03 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   130000Z4 --- 20.8S0 92.4E5
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
110300Z5 POSITION NEAR 17.8S6 92.4E5.
ANIMATED INFRARED SATELLITE IMAGERY SHOWS TROPICAL CYCLONE 04S
(ALISON) HAS TRACKED TOWARDS THE SOUTH OVER THE LAST 12 HOURS.  THE
WARNING POSITION IS BASED ON 102330Z9 INFRARED SATELLITE IMAGERY.
THE WARNING INTENSITY IS BASED ON A COMBINATION OF SATELLITE
DERIVED INTENSITY ESTIMATES.  THE CURRENT WIND RADII HAVE BEEN
ADJUSTED SLIGHTLY BASED ON 100343Z1 SCATTEROMETRY DATA. TC 04S IS
FORECAST TO CONTINUE TRACKING GENERALLY TOWARDS THE SOUTH
THROUGHOUT THE FORECAST PERIOD.  ADDITIONALLY, THE SYSTEM IS
EXPECTED TO WEAKEN DUE TO COLDER SEA SURFACE TEMPERATURES AND
INCREASED WIND SHEAR. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 110000Z2
IS 15 FEET. NEXT WARNINGS AT 111500Z8 (DTG 111351Z2) AND 120300Z6
(DTG 120151Z0).//
=========================================================================
WTXS31 PGTW 981111 14:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 008
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WARNING POSITION:
   111200Z5 --- NEAR 18.3S2 91.7E7
     MOVEMENT PAST SIX HOURS - 205 DEGREES AT 07 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MALSUSTAINED WINDS - 065 KT, GUSTS 080 KT
   RADIUS OF 050 KT WINDS - 020 NM
   RADIUS OF 035 KT WINDS - 075 NM EAST SEMICIRCLE
                            065 NM ELSDWHERE
   REPEAT POSIT: 18.3S2 91.7E7
   FORECASTS:
   12 HRS, VALID AT:
   120000Z3 --- 19.5S5 91.0E0
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   RADIUS OF 050 KT WINDS - 015 NM
   RADIUS OF 035 KT WINDS - 075 NM EAST SEMICIRCLE
     8                      065 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 205 DEG/ 06 KTS
   24 HRS, VALID AT:
   121200Z6 --- 20.5S7 90.5E4
   MAX SUSTAINED WINDS 2 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 065 NM SOUTHEAST SEMICIRCLE
                            055 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 180 DEG/ 06 KTS
   36 HRS, VALID AT:
   130000Z4 --- 21.8S1 90.4E3
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 060 NM EAST SEMICIRCLE
                            050 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 170 DEG/ 07 KTS
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   131200Z7 --- 23.2S7 90.7E6
   MAX SUTAINED WINDS - 035 KT, GUSTS 045 KT
REMARKS:
111500Z8 POSITION NEAR 18.6S5 91.5E5.
ANIMATED INFRARED SATELLITE IMAGERY SHOWS TROPICAL CYCLONE 04S
(ALISON) HAS TRACKED TOWARDS THE SOUTH-SOUTHWEST OVER THE PAST 12
HOURS. THE WARNING POSITION AND INTENSITY ARE BASED ON 111130Z7
INFRARED SATELLITE IMAGERY. TC 04S IS FORECAST TO CONTINUE TRACKING
TOWARDS THE SOUTH THROUGHOUT THE FORECAST PERIOD. ADDITIONALLY, THE
SYSTEM IS EXPECTED TO WEAKEN DUE TO COLDER SEA SURFACE TEMPERATURES
AND INCREASED VERTICAL WIND SHEAR. MAXIMUM SIGNIFICANT WAVE HEIGHT
AT 111200Z5 IS 15 FEET. REFER TO WWIO31 PGFW FOR ADDITIONAL SEA
HEIGHT INFORMATION. NEXT WARNINGS AT 120300Z6 (DTG 120151Z0) AND
121500Z9 (DTG 121351Z3).//
=========================================================================
WTXS31 PGTW 981112 03:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 009
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   120000Z3 --- NEAR 19.5S5 92.0E1
     MOVEMENT PAST SIX HOURS - 160 DEGREES AT 05 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 - 020 NM
   RADIUS OF 035 KT WINDS - 075 NM EAST SEMICIRCLE
                            065 NM ELSEWHERE
   REPEAT POSIT: 19.5S5 92.0E1
    ---
   FORECASTS:
   12 HRS, VALID AT:
   121200Z6 --- 20.4S6 92.2E3
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   RADIUS OF 050 KT WINDS - 015 NM
   RADIUS OF 035 KT WINDS - 075 NM EAST SEMICIRCLE
                            065 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 170 DEG/ 06 KTS
    ---
   24 HRS, VALID AT:
   130000Z4 --- 21.5S8 92.4E5
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 065 NM SOUTHEAST SEMICIRCLE
                            055 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 155 DEG/ 04 KTS
    ---
   36 HRS, VALID AT:
   131200Z7 --- 22.3S7 92.8E9
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   VECTOR TO 48 HR POSIT: 145 DEG/ 04 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   140000Z5 --- 22.9S3 93.3E5
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
120300Z6 POSITION NEAR 19.7S7 92.0E1.
TROPICAL CYCLONE 04S (ALISON) HAS TRACKED SOUTH-SOUTHEASTWARD
AT 5 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION AND INTENSITY
ARE BASED UPON ANIMATED INFRARED SATELLITE IMAGERY. TC 04S (ALISON)
IS FORECAST TO CONTINUE IN A SOUTH-SOUTHEASTWARD TRACK FOR THE
REMAINDER OF THE FORECAST PERIOD. HOWEVER, ANIMATED WATER VAPOR
IMAGERY INDICATED TC 04S (ALISON) IS UNDERGOING MODERATE TO
SEVERE SHEAR. HENCE, TS 04S (ALISON) SHOULD DISSIPATE OVER
WATER BY THE 48 HOUR PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT
AT 120000Z3 IS 15 FEET. NEXT WARNINGS AT 121500Z9 (DTG 121351Z3)
AND 130300Z7 (DTG 130151Z1).//
=========================================================================
WTXS31 PGTW 981112 15:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 010
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   121200Z6 --- NEAR 18.9S8 090.8E7
     MOVEMENT PAST SIX HOURS - 290 DEGREES AT 03 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 - 015 NM
   RADIUS OF 035 KT WINDS - 065 NM
   REPEAT POSIT: 18.9S8 090.8E7
    ---
   FORECASTS:
   12 HRS, VALID AT:
   130000Z4 --- 18.7S6 090.2E1
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 055 NM
   VECTOR TO 24 HR POSIT: 290 DEG/ 03 KTS
    ---
   24 HRS, VALID AT:
   131200Z7 --- 18.5S4 089.6E3
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 045 NM
   VECTOR TO 36 HR POSIT: 285 DEG/ 04 KTS
    ---
   36 HRS, VALID AT:
   140000Z5 --- 18.3S2 088.8E4
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   VECTOR TO 48 HR POSIT: 275 DEG/ 04 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   141200Z8 --- 18.2S1 088.0E6
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
121500Z9 POSITION NEAR 18.9S8  090.6E5.
TROPICAL CYCLONE 04S (ALISON) HAS TRACKED WEST-NORTHWESTWARD AT 3
KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED UPON
121130Z8 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON 121130Z8 SATELLITE INTENSITY ESTIMATES OF 45 KNOTS AND 121030Z7
VISIBLE SATELLITE IMAGERY SHOWING A TIGHTLY WRAPPED LOW-LEVEL
CIRCULATION INDICATIVE OF A MORE INTENSE SYSTEM. TROPICAL CYCLONE
04S (ALISON) IS AN EXPOSED LOW-LEVEL CIRCULATION WITH ITS DEEP
CONVECTION SHEARED TO THE SOUTHEAST. THE FORECAST TRACK CONTINUES
THE SYSTEM TOWADS THE WEST-NORTHWEST BECOMING MORE WESTWARD WITHIN
THE LOW-LEVEL STEERING FLOW. TROPICAL CYCLONE 04S (ALISON) SHOULD
DISSIPATE OVER WATER BY THE END OF THE 48 HOUR FORECAST PERIOD.
MAXIMUM SIGNIFICANT WAVE HEIGHTAT 21200Z6 IS 15 FEET. NEXT
WARNINGS AT 130300Z7 (DTG 130151Z1) AND 131500Z0 (DTG 131351Z4).//
=========================================================================
WTXS31 PGTW 981113 03:00z
1. TROPICAL CYCLONE 04S (ALISON) WARNING NR 011
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   130000Z4 --- NEAR 18.2S1 89.8E5
     MOVEMENT PAST SIX HOURS - 300 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 120 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: 18.2S1 89.8E5
    ---
   FORECASTS:
   12 HRS, VALID AT:
   131200Z7 --- 17.9S7 89.1E8
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
130300Z7 POSITION NEAR 18.1S0  89.6E3.
TROPICAL CYCLONE 04S (ALISON) HAS TRACKED WEST-NORTHWESTWARD
AT 8 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION AND
INTENSITY ARE BASED UPON VISIBLE SATELLITE IMAGERY. TROPICAL
CYCLONE 04S (ALISON) CAN NOT BE DISTINGUISHED ON ANIMATED INFRARED
SATELLITE IMAGERY AS THE CONVECTION ASSOCIATED WITH THE LOW LEVEL
CIRCULATION CENTER HAS SHEARED TO THE SOUTHEAST. TROPICAL CYCLONE
04S (ALISON) IS RAPIDLY DISSIPATING OVER WATER DUE TO THE
AFOREMENTIONED HIGH SHEAR ENVIRONMENT. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 130000Z4 IS 12 FEET. THIS IS THE FINAL WARNING ON THIS
SYSTEM BY THE JOINT TYPHOON WARNING CENTER (NAVPACMETOCCEN WEST
GU).  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_alison_jtwc_advisories.htm Updated: 4 September 2016