Rainfall Update

For the week to 20 March 2018, rainfall was recorded in the north Kimberley and southwest of Western Australia; the Top End in the Northern Territory; the Cape York Peninsula, north tropical, central and southeast coasts of Queensland; southeastern South Australia; south coast of Victoria, and Tasmania.

At the beginning of the week, a weak tropical low formed to the north of the Northern Territory within the monsoon trough that extended from the Timor Sea through the Torres Strait into the northern Coral Sea. Showers and storms with moderate falls developed in Arnhem Land in the Northern Territory. Showers also occurred in the far north of the Cape York Peninsula. A moist onshore flow produced showers along the southeast coast of Queensland and about the central coast of New South Wales. A deep trough extended along the southwest coast of Western Australia, with an embedded low pressure system over the far southwest of Western Australia responsible for showers; moderate falls were recorded in the southwest of the State.

From the middle of the week, the low intensified into tropical cyclone Marcus north of Croker Island in the Northern Territory on the 16th. Marcus tracked southwest and first crossed Darwin, and later the north Kimberley of Western Australia as a category 2 system before moving west away from the Western Australia coast towards the end of week. Tropical cyclone Marcus produced extensive shower and thunderstorm activity with moderate to heavy falls across the Top End, and north Kimberley in Western Australia.

Showers and storms produced moderate falls about the east Arnhem coast of the Northern Territory, across the Cape York Peninsula and along the north tropical coast of Queensland, associated with a developing tropical low over the Torres Strait in the latter part of the week.  

Further south, a significant cold front crossed Tasmania, bringing a middle level cloud band, widespread rainfall, damaging winds and isolated thunderstorms to much of western Tasmania.

The highest weekly total was 296 mm at Warruwi Airport in the northern Arnhem Land coast in the Northern Territory. Rainfall totals in excess of 150 mm were recorded about the coast of the Top End including the Tiwi Islands.

Rainfall totals between 50 mm and 150 mm were recorded in the north Kimberley in Western Australia, the far north of the Top End in the Northern Territory, the tip of Cape York Peninsula and about the north tropical Queensland coast; also in western and northeastern Tasmania.

Rainfall totals between 10 mm to 50 mm were recorded across the remaining parts of the northern Kimberley, the Top End of the Northern Territory, Cape York Peninsula and north tropical Queensland coast; in southeastern Queensland; in the southwest and south coasts of Western Australia; parts of southeastern South Australia along with an area of the south coast of Victoria, and much of Tasmania.

Little or no rainfall was recorded across Western Australia away from the northern Kimberley and southwest coast, the Northern Territory south of the Top End, most of Queensland except the Cape York Peninsula and the east coast, nearly all of New South Wales apart from some areas along the east coast, Victoria away from the south, South Australia except the southeast, and a small part of southeast Tasmania.

Impact of recent rainfall on deficits

The Drought Statement, issued on 5 March 2018, discusses rainfall deficits over Australia for the 9-month (June 2017–February 2018) and 11-month (April 2017–February 2018) periods. Rainfall deficit maps are available for these periods as well as for standard periods.

The maps below show the percentage of mean rainfall that has been received for the rainfall deficit period for the 9- and 11-month periods ending 20 March 2018.

Rainfall for the period 1 June 2017 to 20 March 2018

Serious to severe deficiencies for the 9-month period are present across large areas of western to central Queensland, about the Illawarra, Central Tablelands, Sydney and Hunter regions in New South Wales, and small areas of northern and western New South Wales. Similar deficiencies exist at this timescale about the Flinders Ranges in South Australia, and along the east coast of Tasmania.

Rainfall in the last week had no impact on rainfall deficiencies in affected areas.

Some areas in Queensland's northwest and central west have received at least 100% of their average rainfall for the 9-month period. Remaining affected areas have generally received between 50% and 70% of average for the period.

Rainfall for the period 1 April to 20 March 2018

Serious to severe deficiencies for the 11-month period affect large areas of western to inland central Queensland, and a large area of eastern New South Wales from the Illawarra to the Manning District on the coast, and extending inland towards Narrabri. Deficiencies also persist along the west coast of Western Australia.

Rainfall over the past week had no impact on rainfall deficiencies in affected areas.

Some areas of the inland northwest have now received more than 100% of their average rainfall for the 11-month period. Remaining affected areas of Queensland and New South Wales have generally received between 50% and 70% of average rainfall for the period, while affected areas in Western Australia have received less than 20% to 40% of average.