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Tropical Cyclone ILSA : JTWC Advisories
Season 1999-2000 Summaries (Operational Data): [AU] [SIO] [SPAC] [SH]
---> Tropical Cyclone ILSA Track Map and Data

WTXS22 PGTW 19991210 16:30z
REF/A/RMG/NAVPACMETOCCEN PEARL HARBOR HI/100451Z DEC 99//
AMPN/REF A IS TROPICAL CYCLONE FORMATION ALERT (WTXS21 PGTW
100500)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
250 NM EITHER SIDE OF A LINE FROM 8.4S2 94.5E8 TO 15.1S7 110.9E1
WITHIN THE NEXT 02 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AT 101530Z0 INDICATES THAT A CIRCULATION CENTER IS
LOCATED NEAR 10.1S2 99.1E9. THE SYSTEM IS QUASI-STATIONARY AT 02
KNOTS.
2. REMARKS:
ANIMATED INFRARED SATELLITE IMAGERY AND A 101439Z8 SPECIAL SENSOR
MICROWAVE IMAGER (SSM/I) PASS DEPICT DEEP CONVECTION INCREASING
AND WRAPPING IN TOWARD THE LOW-LEVEL CIRCULATION CENTER FROM THE
NORTH. VERTICAL WINDSHEAR TENDENCY CHART AND 200 MB ANALYSIS
INDICATE THE LLCC IS UNDER A FAVORABLE ENVIRONMENT. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED AT 1003 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS GOOD.
3. THIS ALERT VALID UNTIL 111630Z2.
4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT
LOCATED NEAR 12.5S8 120.6E9.//
=========================================================================
WTXS32 PGTW 19991210 21:00z
SUBJ:  TROPICAL CYCLONE WARNING
1. TROPICAL CYCLONE 01S WARNING NR 001
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   101800Z0 --- NEAR 9.8S7 99.2E0
     MOVEMENT PAST SIX HOURS - 110 DEGREES AT 03 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   REPEAT POSIT: 9.8S7 99.2E0
    ---
   FORECASTS:
   12 HRS, VALID AT:
   110600Z8 --- 10.0S1 99.7E5
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   VECTOR TO 24 HR POSIT: 115 DEG/ 03 KTS
    ---
   24 HRS, VALID AT:
   111800Z1 --- 10.3S4 100.3E4
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   VECTOR TO 36 HR POSIT: 130 DEG/ 03 KTS
    ---
   36 HRS, VALID AT:
   120600Z9 --- 10.7S8 100.8E9
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   VECTOR TO 48 HR POSIT: 130 DEG/ 03 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   121800Z2 --- 11.1S3 101.3E5
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 030 NM NORTHEAST SEMICIRCLE
                            040 NM ELSEWHERE
    ---
REMARKS:
102100Z4 POSITION NEAR 9.8S7 99.3E1.
TROPICAL CYCLONE (TC) 01S, LOCATED APPROXIMATELY 420 NM SOUTHWEST OF
JAVA, HAS TRACKED EAST-SOUTHEASTWARD AT 03 KNOTS DURING THE PAST 6
HOURS. THE WARNING POSITION IS BASED ON 101730Z2 INFRARED SATELLITE
IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT SATELLITE
INTENSITY ESTIMATES OF 30 KNOTS AND SYNOPTIC DATA. ANIMATED INFRARED
SATELLITE IMAGERY DEPICTS CONVECTION HAS INCREASED IN AREAL COVERAGE
OVER THE PAST 12 HOURS. A 101439Z8 SPECIAL SENSOR MICROWAVE IMAGER
(SSM/I) PASS AND A 101354Z4 TROPICAL RAINFALL MEASURING MISSION
(TRMM) PASS INDICATE A WELL DEFINED LOW-LEVEL CIRCULATION CENTER
(LLCC) WITH A CONVECTIVE BAND TO THE NORTH BEGINNING TO WRAP IN
TOWARD THE CENTER. TC 01S IS FORECAST TO TRACK GENERALLY
SOUTHEASTWARD WITHIN A WEAKNESS IN THE SUBTROPICAL RIDGE. TROPICAL
CYCLONE 01S SHOULD INCREASE IN INTENSITY AT A NEAR CLIMATOLOGICAL
RATE AS THE SYSTEM REMAINS UNDER THE UPPER-LEVEL RIDGE. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 101800Z0 IS 12 FEET. THIS WARNING
SUPERSEDES AND CANCELS NAVPACMETOCCEN 101621Z1 DEC 99 TROPICAL
CYCLONE FORMATION ALERT (WTXS22 PGTW 101630 ) NEXT WARNINGS AT
110900Z1 (DTG 110753Z7) AND 112100Z5 (DTG 111953Z0).//
=========================================================================
WTXS31 PGTW 19991211 09:00z COR
1. TROPICAL CYCLONE 01S WARNING NR 002
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   110600Z8 --- NEAR 10.9S0 100.2E3
     MOVEMENT PAST SIX HOURS - 135 DEGREES AT 07 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: 10.9S0 100.2E3
    ---
   FORECASTS:
   12 HRS, VALID AT:
   111800Z1 --- 11.9S1 101.2E4
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 040 NM NORTHEAST SEMICIRCLE
                            030 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 130 DEG/ 06 KTS
    ---
   24 HRS, VALID AT:
   120600Z9 --- 12.6S9 102.1E4
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 065 NM NORTHEAST SEMICIRCLE
                            055 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 115 DEG/ 05 KTS
    ---
   36 HRS, VALID AT:
   121800Z2 --- 13.0S4 103.0E4
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 030 NM
   RADIUS OF 035 KT WINDS - 090 NM NORTHEAST SEMICIRCLE
                            080 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 105 DEG/ 05 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   130600Z0 --- 13.3S7 104.0E5
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   RADIUS OF 050 KT WINDS - 040 NM
   RADIUS OF 035 KT WINDS - 100 NM NORTHEAST SEMICIRCLE
                            085 NM ELSEWHERE
    ---
REMARKS:
110900Z1 POSITION NEAR 11.2S4 100.5E6.
TROPICAL CYCLONE (TC) 01S (ILSA), APPROXIMATELY 315 NM WEST OF
CHRISTMAS ISLAND, HAS TRACKED SOUTHEASTWARD AT 07 KNOTS DURING THE
PAST 6 HOURS. THE WARNING POSITION IS BASED ON 110530Z0 VISIBLE AND
INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON
CURRENT SATELLITE INTENSITY ESTIMATES OF 30 AND 35 KNOTS. ANIMATED
VISIBLE SATELLITE IMAGERY DEPICTS CONVECTION HAS INCREASED IN AREAL
COVERAGE OVER THE PAST 12 HOURS AND BECOME MORE SYMMETRIC AROUND THE
LOW-LEVEL CIRCULATION CENTER (LLCC). A PREVIOUS SCATTEROMETER IMAGE
REVEALED THE STRONGEST WINDS ACROSS THE NORTHERN AND NORTHEASTERN
PORTION OF THE LLCC. TC 01S (ILSA) IS FORECAST TO TRACK GENERALLY
SOUTHEASTWARD WITHIN THE RELATIVELY WEAK STEERING FLOW OF
SUBTROPICAL RIDGING TO THE NORTH. INTERACTION WITH ANOTHER TROPICAL
LOW IN THE TIMOR SEA AND A MID LEVEL LOW OFF WESTERN AUSTRALIA IS
POSSIBLE AFTER THE 48 HOUR PERIOD. TC 01S (ILSA) IS FORECAST TO
INTENSIFY AT A NEAR CLIMATOLOGICAL RATE THROUGH THE INITIAL 36
HOURS WITH INCREASING SHEAR, CURRENTLY SOUTH OF THE SYSTEM,
INHIBITING SOME INTENSIFICATION AFTER THIS PERIOD. JUSTIFICATION:
CORRECTED MANOP. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 110600Z IS 14
FEET. NEXT WARNINGS AT 112100Z5 (DTG 111953Z0) AND 120900Z2 (DTG
120753Z8).//
=========================================================================
WTXS31 PGTW 19991211 21:00z
1. TROPICAL CYCLONE 01S WARNING NR 003
   02 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   111800Z1 --- NEAR 11.5S7 101.5E7
     MOVEMENT PAST SIX HOURS - 115 DEGREES AT 07 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 045 NM NORTHEAST SEMICIRCLE
                            035 NM ELSEWHERE
   REPEAT POSIT: 11.5S7 101.5E7
    ---
   FORECASTS:
   12 HRS, VALID AT:
   120600Z9 --- 12.0S3 102.6E9
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 065 NM NORTHEAST SEMICIRCLE
                            050 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 125 DEG/ 05 KTS
    ---
   24 HRS, VALID AT:
   121800Z2 --- 12.5S8 103.4E8
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 030 NM
   RADIUS OF 035 KT WINDS - 090 NM NORTHEAST SEMICIRCLE
                            080 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 110 DEG/ 05 KTS
    ---
   36 HRS, VALID AT:
   130600Z0 --- 12.8S1 104.3E8
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 030 NM
   RADIUS OF 035 KT WINDS - 090 NM NORTHEAST SEMICIRCLE
                            080 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 100 DEG/ 05 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   131800Z3 --- 13.0S4 105.4E0
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 080 NM NORTHEAST SEMICIRCLE
                            070 NM ELSEWHERE
    ---
REMARKS:
112100Z5 POSITION NEAR 11.6S8 101.8E0.
TROPICAL CYCLONE (TC) 01S (ILSA), APPROXIMATELY 255 NM WEST-
SOUTHWEST OF CHRISTMAS ISLAND, HAS TRACKED EAST-SOUTHEASTWARD AT 07
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
111730Z3 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON CURRENT SATELLITE INTENSITY ESTIMATES OF 35 AND 45 KNOTS.
ANIMATED INFRARED SATELLITE IMAGERY AND A 111425Z4 SPECIAL SENSOR
MICROWAVE IMAGER (SSM/I) PASS DEPICT DEEP CONVECTION CONTINUES TO
BUILD IN TOWARD THE LOW-LEVEL CIRCULATION CENTER (LLCC) SPECIFICALLY
FROM THE NORTHEAST. IMAGERY ALSO INDICATES A CONVECTIVE BAND
DEVELOPING SOUTHEAST OF THE LLCC. SYNOPTIC DATA SHOWS STRONGER WINDS
OVER THE NORTHERN HALF OF THE SYSTEM. TC 01S (ILSA) IS FORECAST TO
TRACK GENERALLY SOUTHEASTWARD WITHIN THE MID-LEVEL STEERING FLOW OF
THE SUBTROPICAL RIDGE EXTENDING FROM NORTHWEST AUSTRALIA. SEMI-DIRECT
TC INTERACTION WITH TROPICAL CYCLONE 02S OVER THE TIMOR SEA IS
POSSIBLE AFTER THE 36 HOUR PERIOD WHICH MAY INHIBIT FURTHER
INTENSIFICATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 111800Z1 IS 14
FEET. NEXT WARNINGS AT 120900Z2 (DTG 120753Z8) AND 122100Z6
(DTG 121953Z1). REFER TO TROPICAL CYCLONE 02S (NONAME) WARNINGS
(WTXS32 PGTW) FOR TWELVE-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991212 09:00z
1. TROPICAL CYCLONE 01S WARNING NR 004
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   120600Z9 --- NEAR 12.1S4 102.5E8
     MOVEMENT PAST SIX HOURS - 110 DEGREES AT 05 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 060 NM NORTH SEMICIRCLE
                            050 NM ELSEWHERE
   REPEAT POSIT: 12.1S4 102.5E8
    ---
   FORECASTS:
   12 HRS, VALID AT:
   121800Z2 --- 12.5S8 103.5E9
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 070 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 105 DEG/ 05 KTS
    ---
   24 HRS, VALID AT:
   130600Z0 --- 12.8S1 104.5E0
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 085 NM NORTHEAST SEMICIRCLE
                            075 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 095 DEG/ 06 KTS
    ---
   36 HRS, VALID AT:
   131800Z3 --- 12.9S2 105.7E3
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 090 NM NORTH SEMICIRCLE
                            080 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 095 DEG/ 06 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   140600Z1 --- 13.0S4 107.0E8
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 090 NM NORTH SEMICIRCLE
                            080 NM ELSEWHERE
    ---
REMARKS:
120900Z2 POSITION NEAR 12.2S5  102.8E1.
TROPICAL CYCLONE (TC) 01S (ILSA), APPROXIMATELY 200 NM WEST-
SOUTHWEST OF CHRISTMAS ISLAND, HAS TRACKED EAST-SOUTHEASTWARD AT 05
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
120530Z1 VISIBLE SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON CURRENT SATELLITE INTENSITY ESTIMATES OF 45 KNOTS. ANIMATED
VISIBLE SATELLITE IMAGERY REVEALED THE LOW LEVEL CIRCULATION CENTER
(LLCC) HAD BECOME PARTIALLY EXPOSED DURING THE PAST 12 HOURS, BUT
CONVECTION HAS RECENTLY BUILT BACK OVER THE SYSTEM=S CENTER. TC 01S
(ILSA) IS FORECAST TO TRACK GENERALLY EAST-SOUTHEASTWARD WITHIN THE
MID-LEVEL STEERING FLOW OF THE SUBTROPICAL RIDGE EXTENDING WEST FROM
NORTHWESTERN AUSTRALIA. THE SYSTEM IS EXPECTED TO SLOWLY TAKE A MORE
EASTWARD TRACK THROUGHOUT THE FORECAST PERIOD. SEMI-DIRECT TC
INTERACTION WITH TROPICAL CYCLONE 02S (JOHN), OVER THE WESTERN TIMOR
SEA, IS POSSIBLE AFTER THE 36 HOUR PERIOD AS MAY CAUSE TC 01S (ILSA)
TO TAKE A SLIGHTLY EQUATORWARD TRACK. TC 01S (ILSA) IS FORECAST TO
CONTINUE SLOWLY INTENSIFYING DURING THE NEXT 24 HOURS. AFTERWARDS,
INCREASING VERTICAL SHEAR CREATED BY EXPANDING OUTFLOW OVER THE
DOMINANT TROPICAL CYCLONE 02S (JOHN) IS EXPECTED TO INHIBIT FURTHER
DEVELOPMENT. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 120600Z IS 14 FEET.
NEXT WARNINGS AT 122100Z6 (DTG 121953Z1) AND 130900Z3 (DTG
130753Z9). REFER TO TROPICAL CYCLONE  02S (JOHN) WARNINGS (WTXS32
PGTW) FOR TWELVE-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991212 21:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 005
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   121800Z2 --- NEAR 12.5S8 103.5E9
     MOVEMENT PAST SIX HOURS - 105 DEGREES AT 07 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 060 NM NORTH SEMICIRCLE
                            050 NM ELSEWHERE
   REPEAT POSIT: 12.5S8 103.5E9
    ---
   FORECASTS:
   12 HRS, VALID AT:
   130600Z0 --- 12.8S1 104.5E0
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 070 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 100 DEG/ 06 KTS
    ---
   24 HRS, VALID AT:
   131800Z3 --- 13.0S4 105.7E3
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 085 NM NORTHEAST SEMICIRCLE
                            075 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 085 DEG/ 06 KTS
    ---
   36 HRS, VALID AT:
   140600Z1 --- 12.9S2 107.0E8
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 085 NM NORTH SEMICIRCLE
                            075 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 085 DEG/ 07 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   141800Z4 --- 12.8S1 108.5E4
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 085 NM NORTH SEMICIRCLE
                            075 NM ELSEWHERE
    ---
REMARKS:
122100Z6 POSITION NEAR 12.6S9 103.8E2.
TROPICAL CYCLONE (TC) 01S (ILSA), APPROXIMATELY 180 NM SOUTHWEST OF
CHRISTMAS ISLAND, HAS TRACKED EAST-SOUTHESTWARD AT 07 KNOTS DURING
THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 121730Z4 INFRARED
SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON CURRENT
SATELLITE INTENSITY ESTIMATES OF 45 KNOTS. ANIMATED INFRARED
SATELLITE IMAGERY DEPICTS PERSISTENT DEEP CONVECTION PARTICULARLY TO
THE NORTHWEST OF THE LOW-LEVEL CIRCULATION. IMAGERY ALSO REVEALS
IMPROVED ORGANIZATION OF THE SYSTEM OVER THE PAST 6 HOURS. ENHANCED
INFRARED IMAGERY INDICATES CONTINUED CLOUD TOP COOLING. WATER VAPOR
IMAGERY CONTINUES TO SHOW GOOD OUTFLOW ALOFT. TC 01S (ILSA) IS
FORECAST TO TRACK GENERALLY EAST-SOUTHEASTWARD WITHIN THE MID-LEVEL
STEERING FLOW OF THE SUBTROPICAL RIDGE EXTENDING WEST FROM
NORTHWESTERN AUSTRALIA. SEMI-DIRECT TC INTERACTION WITH TROPICAL
CYCLONE 02S (JOHN), OFF THE NORTHWEST COAST OF AUSTRALIA, IS
POSSIBLE AFTER THE 24 HOUR PERIOD WHICH MAY CAUSE TC 01S (ILSA) TO
TAKE A SLIGHTLY EQUATORWARD TRACK. TC 01S (ILSA) IS FORECAST TO
CONTINUE SLOWLY INTENSIFYING DURING THE NEXT 24 HOURS. AFTERWARD,
INCREASING VERTICAL SHEAR CREATED BY TROPICAL CYCLONE 02S (JOHN) IS
EXPECTED TO INHIBIT FURTHER DEVELOPMENT. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 121800Z IS 14 FEET. NEXT WARNINGS AT 130900Z3 (DTG
130753Z9) AND 132100Z7 (DTG 131953Z2). REFER TO TROPICAL CYCLONE
02S (JOHN) WARNINGS (WTXS32 PGTW) FOR SIX-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991213 09:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 006
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   130600Z0 --- NEAR 12.5S8 104.9E4
     MOVEMENT PAST SIX HOURS - 090 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 030 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
   RADIUS OF 035 KT WINDS - 075 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   REPEAT POSIT: 12.5S8 104.9E4
    ---
   FORECASTS:
   12 HRS, VALID AT:
   131800Z3 --- 12.5S8 106.5E2
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 070 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 090 DEG/ 07 KTS
    ---
   24 HRS, VALID AT:
   140600Z1 --- 12.5S8 108.0E9
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 070 NM NORTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 090 DEG/ 07 KTS
    ---
   36 HRS, VALID AT:
   141800Z4 --- 12.5S8 109.5E5
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 070 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 105 DEG/ 09 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   150600Z2 --- 12.9S2 111.3E6
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 080 NM NORTH SEMICIRCLE
                            065 NM ELSEWHERE
    ---
REMARKS:
130900Z3 POSITION NEAR 12.5S8  105.3E9.
TROPICAL CYCLONE (TC) 01S (ILSA), APPROXIMATELY 125 NM SOUTH-
SOUTHWEST OF CHRISTMAS ISLAND, HAS TRACKED TOWARDS THE EAST AT 08
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
130530Z2 INFRARED AND VISIBLE SATELLITE IMAGERY. THE WARNING
INTENSITY IS BASED ON CURRENT SATELLITE INTENSITY ESTIMATES OF 55
KNOTS. ANIMATED VISIBLE IMAGERY REVEALS THE LOW LEVEL CIRCULATION
CENTER (LLCC) OF TC 01S (ILSA) HAS BECOME FULLY EXPOSED AS A RESULT
OF INCREASED EASTERLY SHEAR CREATED BY THE DOMINANT UPPER LEVEL
OUTFLOW OF TC 02S (JOHN). THE LLCC, HOWEVER, REMAINS VERY WELL
WRAPPED AND INTENSE. TC 01S (ILSA) IS FORECAST TO TRACK GENERALLY
TOWARDS THE EAST WITHIN THE MID-LEVEL STEERING FLOW OF EQUATORIAL
RIDGING TO THE NORTH. THE SYSTEM IS EXPECTED TO BEGIN TURNING BACK
TOWARDS THE SOUTH AFTER THE 36 HOUR PERIOD AS TC 02S (JOHN), OFF THE
NORTHWEST COAST OF AUSTRALIA, BEGINS TO MOVE INLAND. TC 01S (ILSA)
IS FORECAST MAINTAIN NEAR ITS CURRENT INTENSITY DURING THE INITIAL
36 HOURS. AFTERWARDS, AS VERTICAL SHEAR BEGINS TO DECREASE, SOME
REINTENSIFICATION IS EXPECTED. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
130600Z IS 14 FEET. NEXT WARNINGS AT 132100Z7 (DTG 131953Z2) AND
140900Z4 (DTG 140753Z0). REFER TO TROPICAL CYCLONE 02S (JOHN)
WARNINGS (WTXS32 PGTW) FOR SIX-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991213 21:00z    
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 007    
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   131800Z3 --- NEAR 12.4S7 106.6E3
     MOVEMENT PAST SIX HOURS - 090 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 075 NM NORTH SEMICIRCLE      
                            060 NM ELSEWHERE
   REPEAT POSIT: 12.4S7 106.6E3
    ---
   FORECASTS:
   12 HRS, VALID AT:
   140600Z1 --- 12.4S7 108.2E1
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 075 NM NORTH SEMICIRCLE      
                            060 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 095 DEG/ 07 KTS
    ---
   24 HRS, VALID AT:
   141800Z4 --- 12.5S8 109.6E6
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 075 NM NORTHEAST SEMICIRCLE  
                            060 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 105 DEG/ 09 KTS
    ---
   36 HRS, VALID AT:
   150600Z2 --- 12.9S2 111.3E6
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 020 NM 
   RADIUS OF 035 KT WINDS - 080 NM NORTH SEMICIRCLE      
                            065 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 115 DEG/ 09 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   151800Z5 --- 13.6S0 113.0E5
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 020 NM 
   RADIUS OF 035 KT WINDS - 080 NM NORTH SEMICIRCLE      
                            065 NM ELSEWHERE
    ---
REMARKS:
132100Z7 POSITION NEAR 12.4S7 107.0E8.
TROPICAL CYCLONE (TC) 01S (ILSA), APPROXIMATELY 130 NM SOUTH-
SOUTHEAST OF CHRISTMAS ISLAND, HAS TRACKED EASTWARD AT 08 KNOTS 
DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 
131730Z5 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED 
ON CURRENT SATELLITE INTENSITY ESTIMATES OF 55 KNOTS. ANIMATED 
INFRARED SATELLITE IMAGERY DEPICTS CONVECTION HAS REFORMED OVER THE 
LOW-LEVEL CIRCULATION CENTER (LLCC) OVER THE PAST 6 HOURS. A 
131359Z2 SPECIAL SENSOR MICROWAVE IMAGER PASS SHOWS THAT THE PRIMARY 
CONVECTIVE BAND IS NORTH OF THE LLCC. TC 01S (ILSA) IS FORECAST TO 
TRACK GENERALLY TOWARDS THE EAST WITHIN THE MID-LEVEL STEERING FLOW 
OF RIDGING TO THE NORTH. THE SYSTEM IS EXPECTED TO BEGIN TURNING 
BACK TOWARDS THE SOUTH AFTER THE 36 HOUR PERIOD AS TC 02S (JOHN) 
BEGINS TO MOVE INLAND. TC 01S (ILSA) IS FORECAST TO MAINTAIN ITS 
CURRENT INTENSITY DURING THE INITIAL 24 HOURS DUE TO SHEAR FROM TC 
02S (JOHN). AFTERWARDS, AS VERTICAL SHEAR BEGINS TO DECREASE, SLIGHT 
REINTENSIFICATION IS EXPECTED. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 
131800Z3 IS 14 FEET. NEXT WARNINGS AT 140900Z4 (DTG 140753Z0) AND 
142100Z8 (DTG 141953Z3). REFER TO TROPICAL CYCLONE 02S (JOHN) 
WARNINGS (WTXS32 PGTW) FOR SIX-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991214 09:00z
SUBJ:  TROPICAL CYCLONE WARNING
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 008
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   140600Z1 --- NEAR 12.1S4 108.4E3
     MOVEMENT PAST SIX HOURS - 075 DEGREES AT 13 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
   RADIUS OF 035 KT WINDS - 075 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   REPEAT POSIT: 12.1S4 108.4E3
    ---
   FORECASTS:
   12 HRS, VALID AT:
   141800Z4 --- 11.8S0 110.1E3
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 075 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 095 DEG/ 08 KTS
    ---
   24 HRS, VALID AT:
   150600Z2 --- 11.9S1 111.8E1
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 075 NM NORTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 100 DEG/ 10 KTS
    ---
   36 HRS, VALID AT:
   151800Z5 --- 12.3S6 113.7E2
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 080 NM NORTH SEMICIRCLE
                            065 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 130 DEG/ 10 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   160600Z3 --- 13.6S0 115.3E0
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 020 NM
   RADIUS OF 035 KT WINDS - 080 NM NORTH SEMICIRCLE
                            065 NM ELSEWHERE
    ---
REMARKS:
140900Z4 POSITION NEAR 12.0S3 108.8E7.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED EAST-NORTHEASTWARD AT
13 KNOTS DURING THE PAST 6 HOURS, SOUTH OF CHRISTMAS ISLAND. THE
WARNING POSITION IS BASED ON 140530Z3 VISIBLE AND INFRARED SATELLITE
IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT
INTENSITY ESTIMATES OF 55 KNOTS. ANIMATED VISIBLE SATELLITE IMAGERY
DEPICTS THE LOW LEVEL CIRCULATION CENTER IS BEGINNING TO MOVE OUT
FROM UNDER THE CONVECTION. THE SYSTEM IS MOVING INTO AN AREA OF
INCREASING VERTICAL WIND SHEAR CAUSED BY THE UPPER-LEVEL OUTFLOW
FROM TC 02S (JOHN). TC 01S (ILSA) IS FORECAST TO TRACK GENERALLY
TOWARDS THE EAST WITHIN THE MID-LEVEL STEERING FLOW. THE TRACK WILL
BECOME MORE SOUTHWARD AFTER THE 36 HOUR PERIOD AS TC 02S (JOHN)
BEGINS TO MOVE INLAND. TC 01S (ILSA) IS FORECAST TO WEAKEN
INITIALLY, THEN REDEVELOP AS TC 02S (JOHN) MOVES INLAND AND WEAKENS.
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 140600Z1 IS 16 FEET. REFER TO
WWPW30 RJTX FOR ADDITIONAL SEA HEIGHT INFORMATION. NEXT WARNINGS
AT 142100Z8 (DTG 141953Z3) AND 150900Z5 (DTG 150753Z1). REFER TO
TROPICAL CYCLONE 02S (JOHN) WARNINGS (WTXS32 PGTW) FOR SIX-HOURLY
UPDATES.//
=========================================================================
WTXS31 PGTW 19991214 21:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 009
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   141800Z4 --- NEAR 11.9S1 110.1E3
     MOVEMENT PAST SIX HOURS - 075 DEGREES AT 09 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
   RADIUS OF 035 KT WINDS - 075 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   REPEAT POSIT: 11.9S1 110.1E3
    ---
   FORECASTS:
   12 HRS, VALID AT:
   150600Z2 --- 12.1S4 112.1E5
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 020 NM NORTH SEMICIRCLE
                            020 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 075 NM NORTH SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 110 DEG/ 11 KTS
    ---
   24 HRS, VALID AT:
   151800Z5 --- 12.9S2 114.2E8
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 020 NM
   RADIUS OF 035 KT WINDS - 075 NM NORTHEAST SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 130 DEG/ 11 KTS
    ---
   36 HRS, VALID AT:
   160600Z3 --- 14.4S9 115.9E6
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   RADIUS OF 050 KT WINDS - 050 NM EAST SEMICIRCLE
                            035 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 100 NM EAST SEMICIRCLE
                            085 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 150 DEG/ 10 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   161800Z6 --- 16.1S8 116.9E7
   MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT
   RADIUS OF 050 KT WINDS - 070 NM EAST SEMICIRCLE
                            050 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 135 NM EAST SEMICIRCLE
                            105 NM ELSEWHERE
    ---
REMARKS:
142100Z8 POSITION NEAR 12.0S3 110.6E8.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED EAST-NORTHEASTWARD AT
9 KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
141730Z6 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS.
ANIMATED SATELLITE IMAGERY DEPICTS THE LOW LEVEL CIRCULATION CENTER
BEGINNING TO MOVE OUT FROM UNDER THE CONVECTION. THE SYSTEM IS
MOVING INTO AN AREA OF MODERATE VERTICAL WIND SHEAR CAUSED BY THE
UPPER-LEVEL OUTFLOW FROM TC 02S (JOHN). TC 01S (ILSA) IS FORECAST TO
TRACK GENERALLY TOWARDS THE EAST WITHIN THE MID-LEVEL STEERING FLOW.
THE TRACK WILL BECOME MORE SOUTHWARD AFTER THE 12 HOUR PERIOD AS TC
02S (JOHN) BEGINS TO MOVE INLAND AND THE MID TO UPPER LEVEL RIDGE TO
THE EAST BECOMES THE DOMINANT STEERING FLOW FOR TC 01S (ILSA). THE
SYSTEM IS FORECAST TO MAINTAIN INTENSITY FOR THE NEXT 24 HOURS, THEN
INTENSIFY CLIMATOLOGICALLY ONCE TC 02S (JOHN) BEGINS TO WEAKEN AND
DISSIPATE. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 141800Z4 IS 16 FEET.
NEXT WARNINGS AT 150900Z5 (DTG 150753Z1) AND 152100Z9 (DTG
151953Z4). REFER TO TROPICAL CYCLONE  02S (JOHN) WARNINGS (WTXS32
PGTW)FOR SIX-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991215 09:00z
SUBJ:  TROPICAL CYCLONE WARNING
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 010
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   150600Z2 --- NEAR 12.4S7 112.4E8
     MOVEMENT PAST SIX HOURS - 105 DEGREES AT 15 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   RADIUS OF 050 KT WINDS - 030 NM
   RADIUS OF 035 KT WINDS - 090 NM NORTH SEMICIRCLE
                            075 NM ELSEWHERE
   REPEAT POSIT: 12.4S7 112.4E8
    ---
   FORECASTS:
   12 HRS, VALID AT:
   151800Z5 --- 13.6S0 114.6E2
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   RADIUS OF 050 KT WINDS - 040 NM NORTH SEMICIRCLE
                            030 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 095 NM NORTH SEMICIRCLE
                            075 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 140 DEG/ 12 KTS
    ---
   24 HRS, VALID AT:
   160600Z3 --- 15.4S0 116.1E9
   MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT
   RADIUS OF 050 KT WINDS - 040 NM
   RADIUS OF 035 KT WINDS - 100 NM NORTHEAST SEMICIRCLE
                            080 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 160 DEG/ 14 KTS
    ---
   36 HRS, VALID AT:
   161800Z6 --- 18.1S0 117.2E1
   MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
   RADIUS OF 050 KT WINDS - 050 NM EAST SEMICIRCLE
                            040 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 100 NM EAST SEMICIRCLE
                            085 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 160 DEG/ 14 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   170600Z4 --- 20.7S9 118.3E3
   MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT
   RADIUS OF 050 KT WINDS - 065 NM EAST SEMICIRCLE
                                   OVER WATER
                            050 NM ELSEWHERE OVER WATER
   RADIUS OF 035 KT WINDS - 120 NM EAST SEMICIRCLE
                                   OVER WATER
                            100 NM ELSEWHERE OVER WATER
    ---
REMARKS:
150900Z5 POSITION NEAR 12.7S0 112.9E3.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED EAST-SOUTHEASTWARD AT
15 KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
150530Z4 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING
INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 55
AND 65 KNOTS. ANIMATED SATELLITE IMAGERY INDICATES CONVECTION
REORGANIZING OVER THE LOW LEVEL CIRCULATION CENTER (LLCC) AS THE
SYSTEM MOVES INTO AN AREA OF FAVORABLE VERTICAL WIND SHEAR. TC 01S
(ILSA) IS FORECAST TO TRACK INCREASINGLY SOUTHWARD INTO NORTHWESTERN
AUSTRALIA, NEAR PORT HEDLAND, AS THE SUBTROPICAL RIDGE TO THE EAST
BECOMES THE DOMINANT STEERING FLOW. THE SYSTEM IS FORECAST TO
INTENSIFY CLIMATOLOGICALLY AS TC 02S (JOHN) WEAKENS AND DISSIPATES.
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 150600Z2 IS 18 FEET. NEXT
WARNINGS AT 152100Z9 (DTG 151953Z4) AND 160900Z6 (DTG 160753Z2).
REFER TO TROPICAL CYCLONE  02S (JOHN) WARNINGS (WTXS32 PGTW) FOR
TWELVE-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991215 21:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 011
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   151800Z5 --- NEAR 13.6S0 114.6E2
     MOVEMENT PAST SIX HOURS - 125 DEGREES AT 14 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   RADIUS OF 050 KT WINDS - 030 NM
   RADIUS OF 035 KT WINDS - 090 NM NORTH SEMICIRCLE
                            075 NM ELSEWHERE
   REPEAT POSIT: 13.6S0 114.6E2
    ---
   FORECASTS:
   12 HRS, VALID AT:
   160600Z3 --- 15.5S1 116.1E9
   MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT
   RADIUS OF 050 KT WINDS - 040 NM NORTHEAST SEMICIRCLE
                            025 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 105 NM NORTHEAST SEMICIRCLE
                            090 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 160 DEG/ 14 KTS
    ---
   24 HRS, VALID AT:
   161800Z6 --- 18.1S0 117.2E1
   MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT
   RADIUS OF 050 KT WINDS - 050 NM NORTHEAST SEMICIRCLE
                            035 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 120 NM NORTHEAST SEMICIRCLE
                            100 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 155 DEG/ 14 KTS
    ---
   36 HRS, VALID AT:
   170600Z4 --- 20.7S9 118.4E4
   MAX SUSTAINED WINDS - 105 KT, GUSTS 130 KT
   RADIUS OF 100 KT WINDS - 015 NM OVER WATER
   RADIUS OF 050 KT WINDS - 080 NM EAST SEMICIRCLE
                                   OVER WATER
                            060 NM ELSEWHERE OVER WATER
   RADIUS OF 035 KT WINDS - 150 NM EAST SEMICIRCLE
                                   OVER WATER
                            130 NM ELSEWHERE OVER WATER
   VECTOR TO 48 HR POSIT: 150 DEG/ 12 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   171800Z7 --- 22.8S2 119.6E7
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
152100Z9 POSITION NEAR 14.1S6 115.0E7.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED SOUTHEASTWARD AT 14
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
151730Z7 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 55 AND 65 KNOTS.
ANIMATED INFRARED SATELLITE IMAGERY DEPICTS CENTRAL COLD COVER OVER
THE LOW LEVEL CIRCULATION CENTER (LLCC). ANIMATED INFRARED SATELLITE
IMAGERY NOW INDICATES THAT TC 01S (ILSA) MAY BE INTENSIFYING AGAIN
WITH NEW CONVECTIVE BAND FORMING SOUTH OF THE LLCC. ANIMATED IMAGERY
ALSO SHOWS THAT VERTICAL WIND SHEAR IS DECREASING AS EVIDENCED BY A
WEAKER THERMAL GRADIENT ON EASTERN EDGE OF SYSTEM. ANIMATED WATER
VAPOR IMAGERY SHOWS THAT TC 01S (ILSA) HAS GOOD OUTFLOW IN THE
WESTERN QUADRANT. TC 01S (ILSA) IS FORECAST TO TRACK INCREASINGLY
SOUTHWARD INTO NORTHWESTERN AUSTRALIA, NEAR PORT HEDLAND, UNDER THE
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO THE EAST. TC 01S
(ILSA) IS FORECAST TO INTENSIFY CLIMATOLOGICALLY AS IT MOVES INTO A
MORE FAVORABLE ENVIRONMENT RESULTING PRIMARILY FROM THE WEAKENING
AND DISSIPATION OF TC 02S (JOHN). MAXIMUM SIGNIFICANT WAVE HEIGHT AT
151800Z IS 18 FEET. NEXT WARNINGS AT 160300Z0 (DTG 160153Z6),
160900Z6 (DTG 160753Z2), 161500Z3 (DTG 161353Z9) AND 162100Z0 (DTG
161953Z5).//
=========================================================================
WTXS31 PGTW 19991216 03:00z    
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 012    
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   160000Z7 --- NEAR 14.6S1 115.6E3
     MOVEMENT PAST SIX HOURS - 135 DEGREES AT 14 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   RADIUS OF 050 KT WINDS - 030 NM 
   RADIUS OF 035 KT WINDS - 090 NM NORTH SEMICIRCLE      
                            075 NM ELSEWHERE
   REPEAT POSIT: 14.6S1 115.6E3
    ---
   FORECASTS:
   12 HRS, VALID AT:
   161200Z0 --- 17.2S0 116.7E5
   MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT
   RADIUS OF 050 KT WINDS - 040 NM NORTHEAST SEMICIRCLE  
                            025 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 105 NM NORTHEAST SEMICIRCLE  
                            090 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 155 DEG/ 13 KTS
    ---
   24 HRS, VALID AT:
   170000Z8 --- 19.6S6 117.8E7
   MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT
   RADIUS OF 050 KT WINDS - 050 NM NORTHEAST SEMICIRCLE  
                            035 NM ELSEWHERE
   RADIUS OF 035 KT WINDS - 120 NM NORTHEAST SEMICIRCLE  
                                   OVER WATER
                            100 NM ELSEWHERE OVER WATER
   VECTOR TO 36 HR POSIT: 155 DEG/ 12 KTS
    ---
   36 HRS, VALID AT:
   171200Z1 --- 21.8S1 118.9E9
   MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   VECTOR TO 48 HR POSIT: 150 DEG/ 10 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   180000Z9 --- 23.5S0 119.9E0
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
160300Z0 POSITION NEAR 15.3S9 115.9E6.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED SOUTHEASTWARD AT 14 
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 
152330Z4 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED 
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 55 KNOTS. ANIMATED 
VISIBLE SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED LOW-LEVEL 
CIRCULATION CENTER (LLCC) APPROXIMATELY 30 NM EAST OF THE DEEP 
CONVECTION. ANIMATED INFRARED SATELLITE IMAGERY SHOWS THAT DEEP 
CONVECTION HAS DECREASED IN AREAL EXTENT AND IS SYMMETRIC. ANIMATED 
WATER VAPOR IMAGERY SHOWS THAT TC 01S (ILSA) HAS GOOD OUTFLOW IN THE 
WESTERN QUADRANT. TC 01S (ILSA) IS FORECAST TO TRACK INCREASINGLY 
SOUTHWARD INTO NORTHWESTERN AUSTRALIA, NEAR PORT HEDLAND, UNDER THE 
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO THE EAST. TC 01S 
(ILSA) HAS YET TO SHOW SIGNS OF RE-INTENSIFICATION, HOWEVER, IT IS 
EXPECTED TO INTENSIFY CLIMATOLOGICALLY AS IT MOVES SOUTHWARD INTO A 
MORE FAVORABLE ENVIRONMENT RESULTING PRIMARILY FROM THE WEAKENING 
AND DISSIPATION OF TC 02S (JOHN). MAXIMUM SIGNIFICANT WAVE HEIGHT AT 
160000Z IS 18 FEET. NEXT WARNINGS AT 160900Z6 (DTG 160753Z2), 
161500Z3 (DTG 161353Z9), 162100Z0 (DTG 161953Z5) AND 170300Z1 (DTG 
170153Z7). REFER TO TROPICAL CYCLONE 02S (JOHN) WARNINGS (WTXS32 
PGTW) FOR SIX-HOURLY UPDATES.//
=========================================================================
WTXS31 PGTW 19991216 09:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 013
   02 ACTIVE TROPICAL CYCLONES IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   160600Z3 --- NEAR 16.1S8 117.3E2
     MOVEMENT PAST SIX HOURS - 130 DEGREES AT 18 KTS
     POSITION ACCURATE TO WITHIN 030 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 070 NM NORTHEAST SEMICIRCLE
                            050 NM ELSEWHERE
   REPEAT POSIT: 16.1S8 117.3E2
    ---
   FORECASTS:
   12 HRS, VALID AT:
   161800Z6 --- 18.6S5 119.3E4
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 065 NM NORTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 155 DEG/ 16 KTS
    ---
   24 HRS, VALID AT:
   170600Z4 --- 21.5S8 120.8E1
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   RADIUS OF 035 KT WINDS - 055 NM NORTHEAST SEMICIRCLE
                                   OVER WATER
                            045 NM ELSEWHERE OVER WATER
   VECTOR TO 36 HR POSIT: 150 DEG/ 14 KTS
    ---
   36 HRS, VALID AT:
   171800Z7 --- 24.0S6 122.3E8
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   VECTOR TO 48 HR POSIT: 140 DEG/ 16 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   180600Z5 --- 26.3S1 124.6E3
   MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
160900Z6 POSITION NEAR 16.7S4  117.8E7.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED SOUTHEASTWARD AT 18
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
160530Z5 VISIBLE SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS.
ANIMATED VISIBLE SATELLITE IMAGERY REVEALS THE LOW LEVEL CIRCULATION
CENTER (LLCC) HAS BECOME COMPLETELY EXPOSED WITH THE CONVECTION
SHEARED ABOUT 70 NM TO THE WEST-SOUTHWEST. TC 01S (ILSA) HAS
ACCELERATED AND IS FORECAST TO CONTINUE TRACKING TOWARD THE
SOUTHWEST UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO
THE EAST. TC 01S (ILSA) IS NO LONGER FORECAST TO SIGNIFICANTLY
RE-INTENSIFY DUE TO CONTINUED NORTHEASTERLY SHEAR CREATED BY A BROAD
UPPER LEVEL HIGH NORTHEAST OF THE SYSTEM. THE ACCELERATED FORWARD
SPEED OF THE SYSTEM WILL ALSO HINDER REDEVELOPEMENT OF CONVECTION.
THE LLCC, HOWEVER, IS EXPECTED TO REMAIN INTACT UNTIL MAKING
LANDFALL BETWEEN THE 12 AND 24 HOUR FORECAST POSITION. TC 01S (ILSA)
IS FORECAST TO  DISSIPATE OVER LAND BY THE END OF THE 48 HOUR
FORECAST PERIOD. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 160600Z IS 17
FEET. NEXT WARNINGS AT 161500Z3 (DTG 161353Z9), 162100Z0 (DTG
161953Z5), 170300Z1 (DTG 170153Z7) AND 170900Z7 (DTG 170753Z3).//
=========================================================================
WTXS31 PGTW 19991216 15:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 014
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   161200Z0 --- NEAR 17.3S1 118.6E6
     MOVEMENT PAST SIX HOURS - 135 DEGREES AT 17 KTS
     POSITION ACCURATE TO WITHIN 045 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 060 NM NORTHEAST SEMICIRCLE
                            045 NM ELSEWHERE
   REPEAT POSIT: 17.3S1 118.6E6
    ---
   FORECASTS:
   12 HRS, VALID AT:
   170000Z8 --- 20.1S3 120.7E0
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   RADIUS OF 035 KT WINDS - 040 NM NORTHEAST SEMICIRCLE
                                   OVER LAND
                            030 NM ELSEWHERE OVER WATER
   VECTOR TO 24 HR POSIT: 160 DEG/ 16 KTS
    ---
   24 HRS, VALID AT:
   171200Z1 --- 23.0S5 122.0E5
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   VECTOR TO 36 HR POSIT: 145 DEG/ 16 KTS
    ---
   36 HRS, VALID AT:
   180000Z9 --- 25.5S2 124.1E8
   MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
161500Z3 POSITION NEAR 18.0S9  119.1E2.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED SOUTHEASTWARD AT 17
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
161130Z2 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 KNOTS. ANIMATED
INFRARED SATELLITE IMAGERY REVEALS THE LOW LEVEL CIRCULATION CENTER
(LLCC) REMAINS COMPLETELY EXPOSED WITH THE CONVECTION SHEARED ABOUT
50 NM TO THE WEST-SOUTHWEST. TC 01S (ILSA) HAS TRACKED WITHIN THE
STEERING FLOW OF THE LOW TO MID-LEVEL SUBTROPICAL RIDGE TO THE EAST-
NORTHEAST. TC 01S (ILSA) IS FORECAST TO CONTINUE TRACKING
SOUTHEASTWARD THROUGHOUT THE ENTIRE FORECAST PERIOD. CONTINUED
NORTHEASTERLY SHEAR CREATED BY A BROAD UPPER LEVEL HIGH TO THE
NORTHEAST OF TC 01S (ILSA) IS FORECAST TO HINDER ANY FUTHER
DEVELOPMENT. THE LLCC, HOWEVER, IS EXPECTED TO REMAIN INTACT UNTIL
MAKING LANDFALL AROUND THE 12 HOUR FORECAST PERIOD. TC 01S (ILSA)
SHOULD THEN DISSIPATE OVER LAND WITHIN 36 HOURS. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 161200Z IS 15 FEET. NEXT WARNINGS AT
162100Z0 (DTG 161953Z5), 170300Z1 (DTG 170153Z7), 170900Z7 (DTG
170753Z3) AND 171500Z4 (DTG 171353Z0).//
=========================================================================
WTXS31 PGTW 19991216 21:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 015
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   161800Z6 --- NEAR 18.6S5 119.3E4
     MOVEMENT PAST SIX HOURS - 155 DEGREES AT 15 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
   RADIUS OF 035 KT WINDS - 065 NM NORTHEAST SEMICIRCLE
                            050 NM ELSEWHERE
   REPEAT POSIT: 18.6S5 119.3E4
    ---
   FORECASTS:
   12 HRS, VALID AT:
   170600Z4 --- 21.0S3 120.3E6
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   VECTOR TO 24 HR POSIT: 155 DEG/ 12 KTS
    ---
   24 HRS, VALID AT:
   171800Z7 --- 23.2S7 121.5E9
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
162100Z0 POSITION NEAR 19.2S2 119.6E7.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED SOUTH-SOUTHEASTWARD AT
15 KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
161730Z8 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS.
ANIMATED INFRARED SATELLITE IMAGERY DEPICTS CONVECTION HAS INCREASED
IN THE PAST 6 HOURS, AND THE LOW-LEVEL CIRCULATION CENTER (LLCC)
APPEARS TO HAVE MOVED APPROXIMATELY 20 NM UNDER THE CONVECTION.
SYNOPTIC DATA INDICATES THAT THE WINDS ARE SYMMETRICAL AROUND
THE LLCC WITH THE 35-KNOT RADIUS APPROXIMATELY 60 NM. RADAR DATA
FROM PORT HEDLAND SUGGESTS THAT THE CONVECTION ASSOCIATED WITH TC
01S (ILSA) IS LOOSELY ORGANIZED AND OF OVERALL MODERATE INTENSITY.
TC 01S (ILSA) HAS TRACKED WITHIN THE STEERING FLOW OF THE MID-LEVEL
SUBTROPICAL RIDGE TO THE EAST. TC 01S (ILSA) IS FORECAST TO CONTINUE
TRACKING SOUTH-SOUTHEASTWARD, UNDER DECREASING NORTHEASTERLY
VERTICAL WIND SHEAR, THROUGH THE PERIOD. TC 01S (ILSA) IS EXPECTED
TO INTENSIFY SLIGHTLY PRIOR TO LANDFALL, AND THEN TO RAPIDLY
DISSIPATE OVER LAND AFTER THE 12 HOUR POINT. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 161800Z IS 15 FEET. NEXT WARNINGS AT 170300Z1 (DTG
170153Z7), 170900Z7 (DTG 170753Z3) AND 171500Z4 (DTG 171353Z0).//
=========================================================================
WTXS31 PGTW 19991217 03:00z    
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 016    
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   170000Z8 --- NEAR 19.3S3 119.8E9
     MOVEMENT PAST SIX HOURS - 155 DEGREES AT 09 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   RADIUS OF 035 KT WINDS - 065 NM NORTHEAST SEMICIRCLE  
                                   OVER WATER
                            050 NM ELSEWHERE OVER WATER
   REPEAT POSIT: 19.3S3 119.8E9
    ---
   FORECASTS:
   12 HRS, VALID AT:
   171200Z1 --- 20.7S9 120.5E8
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   VECTOR TO 24 HR POSIT: 160 DEG/ 07 KTS
    ---
   24 HRS, VALID AT:
   180000Z9 --- 22.0S4 121.0E4
   MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
170300Z1 POSITION NEAR 19.7S7 120.0E3.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED SOUTH-SOUTHEASTWARD AT 
09 KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 
162330Z5 VISIBLE SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED 
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS. 
ANIMATED VISIBLE IMAGERY SHOWS THAT THE LOW-LEVEL CIRCULATION CENTER 
(LLCC) IS EMBEDDED APPROXIMATELY 30 NM INTO THE DEEP CONVECTION. 
SYNOPTIC DATA INDICATES THAT THE WINDS ARE FAIRLY SYMMETRICAL AROUND 
THE LLCC WITH THE 35-KNOT WIND RADIUS OF APPROXIMATELY 60 NM. RADAR 
DATA FROM PORT HEDLAND SUGGESTS THAT THE CONVECTION ASSOCIATED WITH 
TC 01S (ILSA) HAS DECREASED IN AREAL EXTENT AND BECOME POORLY 
ORGANIZED OVER THE PAST 6 HOURS. TC 01S (ILSA) HAS TRACKED WITHIN 
THE STEERING FLOW OF THE MID-LEVEL SUBTROPICAL RIDGE TO THE EAST. TC 
01S (ILSA) IS FORECAST TO CONTINUE TRACKING SOUTH-SOUTHEASTWARD, AND 
TO RAPIDLY DISSIPATE OVER LAND AFTER THE 12 HOUR POINT. MAXIMUM 
SIGNIFICANT WAVE HEIGHT AT 170000Z IS 15 FEET. NEXT WARNINGS AT 
170900Z7 (DTG 170753Z3), 171500Z4 (DTG 171353Z0) AND 172100Z1 (DTG 
171953Z6).//
=========================================================================
WTXS31 PGTW 19991217 09:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 017
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   170600Z4 --- NEAR 19.9S9 120.9E2
     MOVEMENT PAST SIX HOURS - 130 DEGREES AT 08 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 LAND
   REPEAT POSIT: 19.9S9 120.9E2
    ---
   FORECASTS:
   12 HRS, VALID AT:
   171800Z7 --- 21.1S4 121.8E2
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   VECTOR TO 24 HR POSIT: 145 DEG/ 07 KTS
    ---
   24 HRS, VALID AT:
   180600Z5 --- 22.2S6 122.6E1
   MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
170900Z7 POSITION NEAR 20.2S4 121.1E5.
TROPICAL CYCLONE (TC) 01S (ILSA) MADE LANDFALL AT AROUND 170430Z5
APPROXIMATELY 130 NM NORTHEAST OF PORT HEDLAND, AUSTRALIA AS A 55
KNOT SYSTEM. THE WARNING POSITION AND INTENSITY ARE BASED UPON
170530Z6 ANIMATED VISIBLE SATELLITE IMAGERY WITH CURRENT
INTENSITY ESTIMATES OF 35 KNOTS.  ANIMATED VISIBLE SATELLITE
IMAGERY INDICATES THE LOW LEVEL CIRCULATION CENTER IS BECOMING
FULLY EXPOSED AS THE SYSTEM WEAKENS RAPIDLY OVER THE AUSTRALIAN
LANDMASS. TROPICAL CYCLONE 01S IS FORECAST TO CONTINUE TRACKING
SOUTHEASTWARD AS IT DISSIPATES OVER LAND WITHIN THE NEXT 24
HOURS. NEXT WARNINGS AT 171500Z4 (DTG 171353Z0).//
=========================================================================
WTXS31 PGTW 19991217 15:00z
1. TROPICAL CYCLONE 01S (ILSA) WARNING NR 018
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   171200Z1 --- NEAR 20.5S7 121.5E9
     MOVEMENT PAST SIX HOURS - 135 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   REPEAT POSIT: 20.5S7 121.5E9
    ---
   FORECASTS:
   12 HRS, VALID AT:
   180000Z9 --- 21.7S0 122.2E7
   MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
171500Z4 POSITION NEAR 20.8S0 121.7E1.
TROPICAL CYCLONE (TC) 01S (ILSA) HAS TRACKED SOUTHEASTWARD AT
8 KNOTS OVER NORTHWESTERN AUSTRALIA OVER THE PAST 6 HOURS.
THE WARNING POSITION AND INTENSITY ARE BASED UPON ANIMATED
INFRARED SATELLITE IMAGERY WITH CURRENT INTENSITY ESTIMATES
OF 25 AND 30 KNOTS. ANIMATED INFRARED SATELLITE IMAGERY INDICATES
THE MAJORITY OF THE DEEP CONVECTION ASSOCIATED WITH TC 01S HAS
DISSIPATED OVER THE PAST 3 HOURS; TC 01S IS RAPIDLY DISSIPATING
OVER LAND. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT
TYPHOON WARNING CENTER (NAVPACMETOCCEN). 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_ilsa_jtwc_advisories.htm Updated: 4 September 2016