Rainfall Update

For the week to 15 December 2020, rainfall was recorded in Western Australia, the Northern Territory, the western half of South Australia, most of Queensland, eastern parts of New South Wales and western Tasmania.

At the start of the week, a cold front embedded in a westerly flow brought moderate falls to western Tasmania.

To the Australian north-west, at the start of the week, a monsoon trough extended from a tropical low near the Kimberley coast to another low to the south of Indonesia. The first tropical low crossed the far south-west Kimberley coast, and generated extensive areas of cloud and thunderstorms, and moderate to heavy falls over northern and interior Western Australia, and the Northern Territory. The second tropical low moved south-east and crossed the Pilbara coast a couple days later. The weakening low moved slowly south over the interior of Western Australia before dissipating in the state's far south-east. The system and associated cloudband produced showers and thunderstorms with moderate falls across large parts of northern and eastern Western Australia, the north and south of the Northern Territory, and parts of western South Australia at the middle of the week.

In the east, at the start of the week, a surface trough extended from north-west Queensland to the central coast of New South Wales. Thunderstorms and showers developed near the trough, with widespread moderate falls across northern Queensland, and areas of the state's central west, and in north-eastern to the central coast of New South Wales. A large high pressure system crossed the Great Australian Bight and directed a strong, moist onshore flow with heavy showers and thunderstorms streaming onto south-eastern Queensland and north-eastern New South Wales. A surface- and upper-level trough developed off the south-east Queensland and north-east New South Wales coast and produced moderate to heavy falls, with the heavier falls reported in elevated locations.

At the end of the week, the coastal trough stalled near the south-east Queensland coast, with a low pressure system deepening over Fraser Island. The systems produced further widespread heavy falls over south-east Queensland and north-eastern New South Wales.

In the north, widespread thunderstorms and showers were observed over the northern half of the Northern Territory and the Cape York Peninsula during the week.

Rainfall totals in excess of 400 mm were reported in far south-east Queensland, and in pockets of the Northern Rivers and Mid North Coast districts in New South Wales. The highest weekly total was 680 mm at Springbrook Road in the Gold Coast Hinterland in Queensland. Higher totals were reported by some gauges not within the standard Bureau network, including 953 mm at Upper Springbrook Alert.

Rainfall totals in excess of 200 mm were reported around Cygnet Bay in the west Kimberley coast, and a pocket in the Pilbara of Western Australia, and from south-east Queensland to the Mid North Coast of New South Wales.

Rainfall totals in excess of 100 mm were reported in areas of the western Kimberley and Pilbara in Western Australia, in parts of the Top End in the Northern Territory, areas of the Cape York Peninsula, and the area from south-east Queensland to the Mid North Coast District in New South Wales.

Rainfall totals between 10 mm and 50 mm were reported across large parts of northern, central and south-eastern Western Australia; the western half of South Australia, and most of the northern half and western parts of the Northern Territory. Similar totals were recorded across most of northern, central and eastern Queensland, north-eastern and east coast New South Wales, and western Tasmania.

Impact of recent rainfall on deficits

Rainfall deficits over Australia for the 8-month (April–November 2020) period is discussed in the Drought Statement, which was issued on 4 December 2020. 

Rainfall deficit maps are available for this period as well as for standard periods. The map below shows the percentage of mean rainfall that has been received for the rainfall deficit period starting April 2020 and extended to the week ending 15 December 2020.

Rainfall for the period 1 April to 15 December 2020

Serious or severe rainfall deficiencies for the 8-month period are in place in Western Australia across large parts of the southern half of the State, excluding the western Gascoyne and southern parts of the SWLD. Serious rainfall deficiencies are also affecting greater south-east Queensland. 

Rainfall received for the week reduced rainfall deficiencies in the interior parts in Western Australia.

Inland areas of Western Australia have generally received less than 20% their average for the period, while remaining areas in Western Australia and areas in south-east Queensland and have generally received less than 80 % to 40% of their average for the period. Though recent rainfall in central Western Australia has seen parts report their average rainfall for the period.