Short-term rainfall deficiencies increase in southeastern Australia
Rainfall for April was below to very much below average across Victoria, New South Wales, eastern South Australia, most of Tasmania, the South West Land Division and south coast in Western Australia, and for large areas of southeastern, far northern, and central inland Queensland. Rainfall was the lowest on record for the month at a number of stations in Victoria, and New South Wales. For southern Australia as a whole, rainfall was the third-lowest on record for April.
The first quarter of 2018 has been marked by an extended period of particularly dry weather for much of mainland southeastern Australia. January to April was the seventh-driest such period for southeastern Australia as a whole. The spatial extent and severity of rainfall deficiencies affecting the southeast has increased compared to the preceding 3-month period, and we are now tracking the four-month period starting in January 2018 (see below). We will also continue to monitor deficiencies at a range of short timescales, as the southern wet season progresses (the southern wet season spans April to November).
Compared to the previous Drought Statement, deficiencies at longer timescales have increased in inland Queensland, the New South Wales central coast and inland eastern areas, Gippsland in Victoria, eastern Tasmania, and along the west coast of Western Australia.
4-month rainfall deficiencies
A particularly dry April across western and southern New South Wales, and the Central District and Gippsland in Victoria has increased rainfall deficiencies across the mainland southeast.
Serious to severe rainfall deficiencies are in place across most of Victoria except the northeast, most of southeastern and agricultural South Australia south and east of Port Augusta, and large areas of New South Wales in west, western Riverina, North West Slopes and Plains, and inland northeast. Scattered pockets of serious or severe deficiencies extend into southwestern Queensland, about Kati Thanda–Lake Eyre in South Australia, and about Shark Bay on the west coast of Western Australia.
13-month rainfall deficiencies
Compared to the 12-month period discussed in the previous Drought Statement, rainfall deficiencies have increased in all affected States.
Serious to severe rainfall deficiencies remain across a large area of eastern to central New South Wales extending along the coast from around Batemans Bay to around New Castle and reaching well inland into the Tablelands and Central West Slopes and Plains; large areas of central and southern to southwestern Queensland; and scattered areas of northern and western New South Wales, western Queensland, and pastoral South Australia between Kati Thanda–Lake Eyre and the coast about Ceduna and Gulf St Vincent.
Serious or severe deficiencies were also present across much of Gippsland in eastern Victoria, along the east coast of Tasmania, and in a broad strip along the west coast of Western Australia between about Karratha and the northern South West Land Division, as well as small areas in the Southwest District.
Soil moisture in the lower layer (from 10 cm to 100 cm deep) for April decreased over most of Australia. Soil moisture increased over parts of northern inland Queensland.
Lower-layer soil moisture was above average across much of northern and western Queensland, adjacent parts of the Northern Territory, parts of eastern Western Australia, and parts of Tasmania.
Soil moisture was below average for most of most of New South Wales, Victoria, South Australia, much of the west of Western Australia, and large parts of the Northern Territory away from the southeast.
- April rainfall was below average for large areas of southern Australia
- Total rainfall for Australia was the the eighth-lowest on record for April
- Exceptionally warm weather during April exacerbated the effect of low rainfall
- The very dry start to the year for the mainland southeast has continued, with deficiencies evident at the 4-month timescale
- Rainfall deficiencies have increased slightly in both the east and west of the country at the 13-month timescale
- Lower-layer soil moisture was below average for April across eastern South Australia, New South Wales, and Victoria
Product code: IDCKGD0AR0
Soil moisture details are reported when there are periods of significant rainfall deficits.
Soil moisture data is from the Bureau's Australian Water Resources Assessment Landscape (AWRA-L) model, developed through the Water Information Research and Development Alliance between the Bureau and CSIRO.
See: Australian Landscape Water Balance.
What is drought?
Drought is a prolonged, abnormally dry period when the amount of available water is insufficient to meet our normal use. Drought is not simply low rainfall; if it was, much of inland Australia would be in almost perpetual drought. Because people use water in so many different ways, there is no universal definition of drought. Meteorologists monitor the extent and severity of drought in terms of rainfall deficiencies. Agriculturalists rate the impact on primary industries, hydrologists compare ground water levels, and sociologists define it by social expectations and perceptions.
It is generally difficult to compare one drought to another, since each drought differs in the seasonality, location, spatial extent and duration of the associated rainfall deficiencies. Additionally, each drought is accompanied by varying temperatures and soil moisture deficits.
Rainfall averages, variability and trends
- Average rainfall: How much rain do you expect?
- Rainfall variability: How consistent is rainfall in your area?
- Rainfall history: Check tables, graphs and data from your local weather station.
- Rainfall trends: Has your rainfall changed?
Lowest on record - lowest since at least 1900 when the data analysed begin.
Severe deficiency - rainfalls in the lowest 5% of historical totals.
Serious deficiency - rainfalls in the lowest 10% of historical totals, but not in the lowest 5%.
Very much below average - rainfalls in the lowest 10% of historical totals.
Below average - rainfalls in the lowest 30% of historical totals, but not in the lowest 10%.
Average - rainfalls in the middle 40% of historical totals.
Above average - rainfalls in the highest 30% of historical totals, but not in the highest 10%.
Very much above average - rainfalls in the highest 10% of historical totals.
For the week to 22 May 2018, rainfall was recorded in coastal eastern Queensland and adjacent inland parts of the State, across southeastern South Australia, southern Victoria, and western Tasmania.
At the beginning of the week, a fast-moving cold front and surface trough tracked across southeastern Australia, with light falls reported in parts of southern South Australia, central and eastern Victoria, and western Tasmania. In the north, widespread showers occurred along coastal and adjacent inland parts of eastern Queensland in response to an upper-level disturbance and moist onshore southeasterly winds.
A high pressure system located over the Bight directed a west to southwesterly flow and brought moderate falls to western Tasmania.
During the middle of the week, the westerly flow and a series of embedded cold fronts produced light falls in southeastern Western Australia, southeastern South Australia, southwest Victoria, and moderate falls in western Tasmania and parts of the exposed southern coast of Victoria.
At the end of the week a trough and cold front produced thick cloud over southeastern Australia. Moderate falls were recorded in southern Victoria and western Tasmania, with light falls extending into southeastern South Australia and into central Victoria.
Moist onshore flow continued to produce showers about the north tropical coast of Queensland for the rest of the week.
Rainfall totals in excess of 100 mm were recorded in in the West Coast (Mountain Region) of Tasmania, including the highest recorded weekly total of 300 mm at Mount Read. Due to a network outage, Mount Read's true total is presently unknown but certainly higher.
Rainfall totals between 50 mm and 100 mm were recorded in western Tasmania and around Innisfail on the north tropical Queensland coast.
Rainfall totals between 25 mm and 50 mm were recorded in southwestern Victoria between Warrnambool and Cape Otway, and across much of West and South Gippsland in the east of that State, in an area near Adelaide in South Australia, and about Queensland's north tropical coast between Cairns and Tully.
Rainfall totals between 10 mm and 25 mm were recorded in southeastern Western Australia near Eucla; about the Mount Lofty Ranges, Kangaroo Island and Lower South East districts in South Australia; and surrounding higher falls across much of southern Victoria and in western Tasmania.
Little or no rainfall was recorded in Western Australia, the Northern Territory, South Australia away from the southeast, northwestern and central northern Victoria, and parts of East Gippsland, northeastern Tasmania, New South Wales, and Queensland away from the east coast and adjacent inland districts.
Impact of recent rainfall on deficits
The Drought Statement, issued on 3 May 2018, discusses rainfall deficits over Australia for the 4-month (January–April 2018) period 13-month (April 2017–April 2018). 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 4-month 13-month periods ending 22 May 2018.
Rainfall for the period 1 January to 22 May 2018
Serious to severe deficiencies for the 4-month period affect most of Victoria except the northeast, most of South Australia south and east of Port Augusta, and large areas of New South Wales in the western Riverina, North West Slopes and Plains, and inland northeast. Pockets of serious to severe deficiencies extend into southwestern Queensland, around Lake Eyre in South Australia, and near Shark Bay on the west coast of Western Australia.
Rainfall in the past week easied deficiencies ever so slightly in parts of West Gippsland in Victoria.
Affected areas of central and western New South Wales and northwestern Victoria have mostly received between 20% and 30% of average rainfall for the period. Affected areas along southern Victoria and coastal southeastern South Australian received less than 60% of average for the period, decreasing as further inland.
Rainfall for the period 1 April 2107 to 22 May 2018
Serious to severe deficiencies for the 13-month period are in place across a large area of eastern to central New South Wales extending along the coast from around Batemans Bay to Newcastle and reaching well inland into the Tablelands and Central West Slopes and Plains; also in large areas of central and southern to southwestern Queensland. Smaller areas are also affected in northern and western New South Wales, western Queensland, and pastoral South Australia between Lake Eyre and the coast about Ceduna and Gulf St Vincent. Deficiencies also affect much of Gippsland in eastern Victoria, along the east coast of Tasmania, and a broad strip along the west coast of Western Australia from Karratha to the northern South West Land Division, as well as small areas in the Southwest District.
Rainfall in the last week as had very little effect on deficiencies.
Affected areas of Queensland and New South Wales have received between 30% and 60% of average rainfall for the period. Affected areas about the northwest coast of Western Australia have generally received between 30% and 20% of average, with areas further south reaching 70% of average for the period.
Product code: IDCKGRWAR0