Subject: Indian-S: 01 Active Tropical Cyclone In Southern Hemisphere

From: SIU Weather Processor <[email-masked]>
Date: Mon, 7 Dec 1998 14:23:11 -0600

690
WTXS32 PGTW 072100
1. TROPICAL CYCLONE 06S (THELMA) WARNING NR 006
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   071800Z6 --- NEAR 10.9S0 130.5E9
     MOVEMENT PAST SIX HOURS - 210 DEGREES AT 06 KTS
     POSITION ACCURATE TO WITHIN 030 NM
     POSITION BASED ON EYE FIXED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 115 KT, GUSTS 140 KT
   RADIUS OF 100 KT WINDS - 020 NM
   RADIUS OF 050 KT WINDS - 030 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            050 NM ELSEWHERE OVER WATER
   RADIUS OF 035 KT WINDS - 100 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            115 NM ELSEWHERE OVER WATER
   REPEAT POSIT: 10.9S0 130.5E9
    ---
   FORECASTS:
   12 HRS, VALID AT:
   080600Z4 --- 11.5S7 130.1E5
   MAX SUSTAINED WINDS - 110 KT, GUSTS 135 KT
   RADIUS OF 100 KT WINDS - 015 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            020 NM ELSEWHERE OVER WATER
   RADIUS OF 050 KT WINDS - 035 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            050 NM ELSEWHERE OVER WATER
   RADIUS OF 035 KT WINDS - 120 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            110 NM ELSEWHERE OVER WATER
   VECTOR TO 24 HR POSIT: 215 DEG/ 04 KTS
    ---
   24 HRS, VALID AT:
   081800Z7 --- 12.1S4 129.7E9
   MAX SUSTAINED WINDS - 110 KT, GUSTS 135 KT
   RADIUS OF 100 KT WINDS - 020 NM
   RADIUS OF 050 KT WINDS - 050 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            040 NM ELSEWHERE OVER WATER
   RADIUS OF 035 KT WINDS - 090 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            095 NM ELSEWHERE OVER WATER
   VECTOR TO 36 HR POSIT: 225 DEG/ 05 KTS
    ---
   36 HRS, VALID AT:
   090600Z5 --- 12.8S1 129.0E2
   MAX SUSTAINED WINDS - 105 KT, GUSTS 130 KT
   RADIUS OF 100 KT WINDS - 015 NM
   RADIUS OF 050 KT WINDS - 050 NM SOUTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 090 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            110 NM ELSEWHERE OVER WATER
   VECTOR TO 48 HR POSIT: 240 DEG/ 06 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   091800Z8 --- 13.4S8 128.0E1
   MAX SUSTAINED WINDS - 105 KT, GUSTS 130 KT
   RADIUS OF 100 KT WINDS - 015 NM
   RADIUS OF 050 KT WINDS - 060 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            050 NM ELSEWHERE OVER WATER
   RADIUS OF 035 KT WINDS - 105 NM SOUTHEAST SEMICIRCLE
                                   OVER WATER
                            110 NM ELSEWHERE OVER WATER
    ---
REMARKS:
072100Z0 POSITION NEAR 11.1S3  130.4E8.
TROPICAL CYCLONE 06S (THELMA) HAS DRIFTED SOUTH-SOUTHWESTWARD AT 6
KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION AND INTENSITY
(115KTS) ARE  BASED ON 071130Z2 INFRARED SATELLITE IMAGERY
ANALYSIS TECHNIQUES. IMAGERY REVEALS A 19NM RAGGED EYE WITH THE
EYEWALL APPROACHING BATHURST AND MELVILLE ISLANDS, JUST NORTH OF
DARWIN, AUSTRALIA. ANIMATED SATELLITE IMAGERY SHOWS AN INCREASE IN
INTENSITY OVER THE PAST 12 HOURS. ANIMATION ALSO INDICATES A
SLIGHTLY MORE WEST-SOUTHWESTWARD TRACK OVER THE PAST 3 HOURS.
SYNOPTIC OBSERVATIONS AND SATELLITE IMAGERY INDICATE A FAIRLY
CONTRACTED WIND RADII. ALTHOUGH TC 06S (THELMA) IS UNDER THE WEAK
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO ITS SOUTH, ANIMATED
INFRARED AND WATER VAPOR SATELLITE IMAGERY INDICATE AN UPPER LEVEL
TROUGH TO THE SOUTHEAST IS MITIGATING THE STEERING EFFECTS OF THE
RIDGE. THIS MITIGATION EFFECT ALLOWED TC 06S (THELMA) TO DRIFT MORE
TOWARDS THE SOUTH OVER THE PAST 18 HOURS. ACCORDING TO THE NAVAL
OPERATIONAL GLOBAL ATMOSPHERIC PREDICTION SYSTEM (NOGAPS), THE
TROUGH/RIDGE INTERACTION IS WEAKENING AND SHOULD ONLY AFFECT THE
TRACK OF TC 06S (THELMA) FOR THE NEXT 12-24 HOURS. AFTERWARDS, THE
FORECAST TRACK IS MORE WESTERLY AS THE RIDGE TO THE SOUTH BEGINS TO
BECOME THE PRIMARY STEERING INFLUENCE. THE FORECAST TRACK SPEED
GRADUALLY INCREASES AS THE STEERING FLOW TRANSITIONS.  TC 06S SHOULD
NOW BE AT MAX INTENSITY AS IT BEGINS TO INTERACT WITH THE AUSTRALIAN
ISLANDS AND NORTH COAST. TC 06S (THELMA)=S INTENSIFY IS FORECAST TO
SLOWLY WEAKEN DUE TO THIS INTERACTION. THE WIND RADII ARE BASED UPON
CLIMATOLOGY FOR A SMALLER THAN AVERAGE SIZED SYSTEM, SATELLITE
SIGNATURE, AND AVAILABLE SURFACE SYNOPTIC DATA. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 071800Z6 IS 21 FEET. NEXT WARNINGS AT 080900Z7 (DTG
080753Z3) AND 082100Z1 (DTG 081953Z6). //

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