Tropical Low (12U)

27 January – 7 February 2021 Track of Tropical Low (12U)

Summary

A tropical low developed near the Western Australia/Northern Territory border on 27 January and tracked southwest over land. By 31 January the low was located in the eastern Pilbara and continued moving on a west-southwest track. The speed of movement was very slow and the low was located over the inland Gascoyne by 3 February. On 4 February, after spending nine days over land, it finally moved offshore near Carnarvon at about 8pm. Once over water the low was steered in a southerly direction parallel to the west coast before it moved inland over the southwest corner of Western Australia and then into the Southern Ocean.

The low produced extended periods of heavy rainfall as it moved over the Kimberley, Pilbara and Gascoyne and caused flooding of roads and rivers across those districts. The Gascoyne River reached moderate flooding level and the main highway north sustained significant damage. As the low moved over the southwest corner on 7 and 8 February heavy rainfall was recorded in many agricultural districts. The rainfall also assisted in extinguishing a severe wildfire that had been raging to the northeast of Perth for many days and that had been responsible for the loss of many homes.

Record highest daily rainfall for February were recorded at many locations including (rainfall recorded to 9 am AWST on that date):

153.0mm at Hill Springs on 4 February

139.4mm at Byro on 4 February

121.0mm at Carey Downs on 4 February

101.2mm at Gascoyne Junction on 4 February

137.2mm at Carnarvon Airport on 5 February
96.6mm at Shark Bay Airport on 5 February

88.0mm at Steep Point on 6 February

83.0mm at Tamla on 6 February

98.0mm at Jurien Bay on 7 February

90.5mm at Nambung Station on 7 February

88.8mm at Karridale on 8 February

80.2mm at Kirup on 8 February

73.0mm at Pemberton 8 February

Notable rainfall totals during the event:

In the 72 hours to 9am 31 January:

Myroodah 409.8mm

Debesa 334mm

Liveringa Station 309.8mm

Mount Hart Station 306.6mm

In the 24 hours to 9am 1 February:

Derby Main Roads 123.4mm

Troughton Island 95.8mm

Ripon Hills Road 94.6mm

In the 24 hours to 9am 2 February:

59 Mile Peg 109.4mm

Indee 101.8mm

Black Hills 89mm

In the 24 hours to 9am 3 February:

Connanarrina 112.6mm

Emu Creek 108.8mm

Hill Springs 100mm

In the 24 hours to 9am 4 February:

Hill Springs 153mm

Carey Downs 121mm

Gascoyne Junction 110.2mm

In the 24 hours to 9am 5 February:

Shark Bay Airport 96.6mm

Wahroonga 84mm

Denham 77.2mm

Steep Point 70.6mm

In the 24 hours to 9am 6 February:

Steep Point 88mm

Tamala 83mm

In the 24 hours to 9am 7 February:

Jurien Bay 98mm

Nambung Station 90.5mm

Lancelin East 85mm

Hill River Springs 80.4mm

Moora 74.6mm

Warradarge 62.8mm

Jurien Bay 61.6mm

In the 24 hours to 9am 8 February:

Karridale (DPRID) 88.8mm

Windy Harbour 66.8mm

Collie 62.7mm

Greenbushes 61.4mm

Brennans Ford 56.8mm

Rocky Gully South 56.6mm

Flooding

Kimberley

Fitzroy River Catchment:

Fitzroy River at Fitzroy Crossing reached multiple peaks above minor flood level.

  • 10.86m on 1 February
  • 10.84m on 12 February

Fitzroy River at Noonkanbah reached multiple peaks above minor flood level.

  • 10.35m on 4 February
  • 9.90m on 14 February

Pilbara

De Grey River Catchment:

Oakover River at Ripon Hills Road reached multiple peaks above minor flood level.

  • 3.98m on 2 February
  • 2.85m on 7 February

Nullagine River at Nullagine reached multiple peaks above minor flood level.

  • 2.05m on 1 February
  • 1.22m on 6 February

Lyndon-Minilya Rivers:

Minilya River at Minilya Bridge maintained around moderate flood level for multiple days.

  • Floated around 4m 4 – 6 February.

Gascoyne

Gascoyne River Catchment:

Gascoyne River at Jimba peaked at moderate flood level.

  • 7.01m on 5 February

Gascoyne River at Fishy Pool peaked above minor flood level.

  • 8.45m on 5 February

Gascoyne River at Nine Mile Bridge peaked above moderate flood level.

  • 7.03m on 6 February
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**All information relating to intensity and track is preliminary information based on operational estimates and subject to change following post analysis.**

Extreme values during cyclone event (estimated)

Note that these values may be changed on the receipt of later information

Maximum Category: Tropical Low
Maximum sustained wind speed: 55 km/h
Maximum wind gust: 80 km/h
Lowest central pressure: 990 hPa