AXAU01 APRF 111305
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 1305 UTC 11/04/2021

Name: Severe Tropical Cyclone Seroja
Identifier: 22U
Data At: 1200 UTC
Latitude: 28.1S
Longitude: 114.3E
Location Accuracy: within 10 nm [20 km]
Movement Towards: southeast [134 deg]
Speed of Movement: 29 knots [53 km/h]
Maximum 10-Minute Wind: 65 knots [120 km/h]
Maximum 3-Second Wind Gust: 90 knots [165 km/h]
Central Pressure: 971 hPa
Radius of 34-knot winds NE quadrant: 110 nm [205 km]
Radius of 34-knot winds SE quadrant: 70 nm [130 km]
Radius of 34-knot winds SW quadrant: 50 nm [95 km]
Radius of 34-knot winds NW quadrant: 80 nm [150 km]
Radius of 48-knot winds NE quadrant: 60 nm [110 km]
Radius of 48-knot winds SE quadrant: 35 nm [65 km]
Radius of 48-knot winds SW quadrant: 25 nm [45 km]
Radius of 48-knot winds NW quadrant: 40 nm [75 km]
Radius of 64-knot winds:
Radius of Maximum Winds: 15 nm [30 km]
Dvorak Intensity Code: T4.0/4.5/S0.0/24HRS STT:W0.5/06HRS
Pressure of outermost isobar: 1000 hPa
Radius of outermost closed isobar: 100 nm [185 km]

FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 11/1800: 30.1S 116.8E: 045 [085]: 050 [095]: 983
+12: 12/0000: 32.5S 120.1E: 065 [120]: 035 [065]: 990
+18: 12/0600: 34.8S 123.3E: 085 [155]: 030 [055]: 995
+24: 12/1200: : : :
+36: 13/0000: : : :
+48: 13/1200: : : :
+60: 14/0000: : : :
+72: 14/1200: : : :
+96: 15/1200: : : :
+120: 16/1200: : : :

REMARKS:
Current position of Tropical Cyclone Seroja accuracy is high due to the system being visible on radar coverage, ground observations and also a ragged eye apparent on IR satellite imagery.

An eye pattern over the last 6 hours has resulted in a T4.5 [T5.0 with -0.5 modifier due to a ragged eye]. Latest imagery shows cloud top warming on the western side of the system reducing DT to 4.0, though the system has recently crossed the coast. Latest MET is 4.5 based on a D- trend, with PAT reduced to 4.0. FT set at 4.0 and CI held at 4.5. Raw ADT were increasing prior to landfall
with 4.7 [CIMSS] and 4.3 [NESDIS] using EYE pattern. SATCON has not updated recently. Intensity set at 65kt [10-minute]. A SMAP pass at 0635UTC identified strongest winds to the east, peaking above 80 knots [1-minute]. Microwave passes
at 0637 and 0940 showed a large band of deep convection around the northern quadrants and a clear eye.

TC Seroja is being steered towards the southeast by a mid-level high to the northeast and an approaching mid-latitude trough to the southwest and has made landfall just south of the town of Kalbarri on the west coast of Western Australia. Multiple surface observations inland of the crossing point have recorded gusts between 70 and 75 knots with a non-standard observing site nearer the coast reporting a 90 knot gust at 1103 UTC.

CIMSS shear at 06Z was analysed as 9 knots. Seroja reached Category 3 intensity this morning, with an asymmetric structure and the hurricane force winds have only been to the north and east of the system centre, with the northeast quadrant being enhanced by the rapid translation speed. Good poleward outflow has developed in the last 6 hours and is evident on satellite imagery and CIMSS analysis is indicating strong upper divergence over the system at 09UTC.

Seroja will weaken as it continues moving rapidly inland.

Copyright Commonwealth of Australia
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The next bulletin for this system will be issued by: 11/1930 UTC.
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