• 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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