Indian-S: TC 18S W017
From
Weather Alert@21:1/175 to
All on Thu Feb 4 20:50:00 2021
WTXS31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 017//
RMKS/
1. TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 017
01 ACTIVE TROPICAL CYCLONE IN SOUTHIO
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
041200Z --- NEAR 24.6S 113.4E
MOVEMENT PAST SIX HOURS - 235 DEGREES AT 03 KTS
POSITION ACCURATE TO WITHIN 040 NM
POSITION BASED ON CENTER LOCATED BY A COMBINATION OF
SATELLITE, RADAR AND SYNOPTIC DATA
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 030 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
045 NM NORTHWEST QUADRANT
REPEAT POSIT: 24.6S 113.4E
---
FORECASTS:
12 HRS, VALID AT:
050000Z --- 24.9S 113.0E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 010 NM NORTHEAST QUADRANT
050 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
010 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 195 DEG/ 04 KTS
---
24 HRS, VALID AT:
051200Z --- 25.6S 112.8E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT
090 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 165 DEG/ 06 KTS
---
36 HRS, VALID AT:
060000Z --- 26.8S 113.1E
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
---
REMARKS:
041500Z POSITION NEAR 24.7S 113.3E.
04FEB21. TROPICAL CYCLONE (TC) 18S (EIGHTEEN), LOCATED APPROXIMATELY
143 NM SOUTH-SOUTHWEST OF LEARMONTH, AUSTRALIA, HAS TRACKED
SOUTHWESTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS FLARING DEEP CONVECTION
EAST OF A DEFINED LOW-LEVEL CIRCULATION CENTER, WHICH SUPPORTS THE
INITIAL POSITION WITH GOOD CONFIDENCE. THE CENTER IS LOCATED
APPROXIMATELY 22NM NORTHWEST OF CARNARVON, WHICH IS REPORTING
SUSTAINED SURFACE WINDS (10-MINUTE AVERAGE) OF 23 KNOTS WITH GUSTS
TO 33 KNOTS; THE CURRENT SLP VALUE IS 993.1MB, WHICH TYPICALLY
CORRESPONDS TO A 35-40 KNOT TROPICAL CYCLONE, WITH A 24-HOUR SLP
DECREASE OF 6.1MB. A 040215Z ASCAT-B IMAGE REVEALS AN EXTENSIVE
SWATH OF 30-35 KNOT WINDS OVER WATER TO THE SOUTHWEST ASSOCIATED
WITH A LARGE FIELD OF STABLE, COOL-AIR STRATOCUMULUS AS EVIDENT IN
EIR. OVERALL, THIS DATA SUPPORTS THE INITIAL INTENSITY ASSESSMENT OF
35 KNOTS. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE UPPER-LEVEL
CONDITIONS WITH LOW VERTICAL WIND SHEAR (VWS) AND POLEWARD VENTING
INTO THE WESTERLIES TO THE SOUTH. HOWEVER, INTERACTION WITH LAND,
DRY AIR ENTRAINMENT AND MARGINAL SST VALUES (25-26C) WILL HINDER
DEVELOPMENT. TC 18S IS TRACKING ALONG THE NORTHERN PERIPHERY OF A
LOW-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTH BUT IS
EXPECTED TO TURN SOUTHWARD AS A STR BUILDS EAST OF THE SYSTEM OVER
WESTERN AUSTRALIA. DUE TO THE SOUTHWARD TRACK, THE SYSTEM WILL MOVE
UNDER THE SUBTROPICAL WESTERLIES WITH INCREASING VWS (30-45 KNOTS),
WHICH WILL LEAD TO STEADY WEAKENING AND EVENTUAL DISSIPATION BY TAU
36. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT LENDING HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK, WHICH IS POSITIONED NEAR THE
MULTI-MODEL CONSENSUS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 041200Z IS
18 FEET. NEXT WARNINGS AT 042100Z, 050300Z, 050900Z AND 051500Z.//
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