Rainfall deficiencies persist in Tasmania, emerge near the west coast of Western Australia
May rainfall was below to very much below average across much of Western Australia, with large areas along the west coast and in the interior in decile 1 (lowest 10% of historical observations). Rainfall was also below average for large areas of South Australia in the west, south, and central east; northwestern New South Wales; and for much of Victoria away from the west, northern country, and far east. Following below average rainfall near the west coast of Western Australia in April, deficiencies are now emerging.
The Northern Territory, the northern Kimberley, and parts of northwestern to central northern Queensland also observed below average rainfall for the month, but May forms the first month of the dry season for northern Australia, and average rainfall is typically low for the months May to September. While areas of southwestern Queensland and the southeastern Northern Territory experienced a dry end to the wet season; significant rainfall totals are not likely before the return of the wet season.
3-month rainfall deficiencies
The west of Western Australia has experienced below average rainfall for both April and May, seeing the emergence of serious and severe rainfall deficiencies for the 3-month period in a broad area between Exmouth and the region north of Perth. Serious rainfall deficiencies have also emerged in pockets of the southern South West Land Division in Western Australia and on the Eyre Peninsula in South Australia. The Climate Outlook for June to August indicates that a drier than average winter is likely across the south of both Western Australia and South Australia.
In Tasmania rainfall deficiencies remain at the 3-month timescale, covering the western highlands region.
Soil moisture in the lower layer (from 10 cm to 100 cm deep) decreased for May compared to April across the west and south of Western Australia, the Northern Territory, western Tasmania, and eastern New South Wales. Soil mositure increased across the interior of Western Australia and central South Australia.
Soil moisture for May was below average for the South West Land Division, western Gascoyne and western Pilbara in Western Australia; the Eyre Peninsula and pockets around Gulf St Vincent in South Australia; western and southern Tasmania; and a large area extending through the southeast of the Northern Territory and Queensland's west and the Maranoa and Warrego district.
Soil moisture for the month was above average for most of the Kimberley and the interior of Western Australia; the Top End and adjacent north of the Northern Territory; the south of the Cape York Peninsula in Queensland and an area of the east coast extending from around Townsville in northern Queensland to northeastern New South Wales; western and southern Tasmania; and across an area extending from central South Australia through the southwest of New South Wales and the western half of Victoria.
- May rainfall was below average for most of Western Australia, large parts of South Australia and Victoria, and northwestern New South Wales
- Serious to severe rainfall deficiencies are present at the 3-month timescale near the west coast of Western Australia, the Eyre Peninsula in South Australia, and the western highlands of Tasmania
- Soil moisture is below average across the west of Western Australia, much of inland Queensland and western parts of the Northern Territory, the Eyre Peninsula in South Australia, and western Tasmania
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 27 June 2017, rainfall was recorded in southwestern and central parts of Western Australia; central Pastoral and coastal parts of South Australia; along the west coast and in South and West Gippsland in Victoria; in western and northern Tasmania; and along the north tropical coast in Queensland. Much of Victoria and northeastern New South Wales also recorded some light falls.
During the first part of the week, a low pressure system deepened near the southwest of Western Australia. Widespread showers with moderate to heavy falls were observed in southwest Western Australia and the southern Goldfields. Localised very heavy falls were recorded in the northern Great Southern district as the low moved slowly inland near the southwest coast before weakening and moving northwest-ward along the coast by mid-week. An inland trough and associated cloudband ahead of the low extended from the northwest to the south coast of Western Australia and moved across southern South Australia during the middle of the week, producing mostly light rainfall in central Western Australia and across the Nullarbor.
A middle level trough extending from the northwest of Western Australia developed with an associated cloudband and moved east through South Australia later in the week. Moderate rainfall was recorded in central Western Australia and central Pastoral areas in South Australia, while an onshore flow brought some falls to the south coast of Western Australia.
A westerly flow followed by a cold front produced light to moderate rainfall to western Tasmania and light falls in southern Victoria at the start of the week.
In the middle of the week, a second cold front crossed the southeast of the continent bringing moderate rainfall to western Tasmania and light falls in northern Tasmania and southern Victoria.
An onshore flow produced moderate falls to the north tropical coast in Queensland throughout the week.
Rainfall totals between 50 mm and 100 mm were recorded in a small area in the Lower West district around Perth, with localised higher falls in excess of 100 mm in the northern parts of the Great Southern district in Western Australia. Western Tasmania also recorded rainfall totals between 50 mm and 100 mm, with the highest national weekly total of 139 mm recorded at Mount Read.
Rainfall totals between 10 mm and 50 mm were recorded in much of the southern half of Western Australia, including the South West Land Division away from the northeast parts, the Eucla coast, Goldfields and the Southern Interior. Weekly totals in excess of 15 mm were recorded in the central Pastoral region in South Australia, on the southwest coast and in South and West Gippsland in Victoria, and across western and northern Tasmania. Totals in western Tasmania were in excess of 50 mm. The north tropical coast of Queensland also recorded rainfall totals between 10 mm to 50 mm.
Little or no rainfall was recorded in the northern half of Western Australia, western and eastern South Australia away from the extreme southeast, and most of the Northern Territory, Queensland, and New South Wales.
Impact of recent rainfall on deficits
The Drought Statement, issued on 5 June 2017, discusses rainfall deficits over Australia for the 3-month (March-May 2017) period. The rainfall deficit map is 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 for the 3-month periods ending 27 June 2017.
Compared to last week, serious to severe rainfall deficiencies near the west coast of Western Australia and the Eyre Peninsula in South Australia have persisted, while the deficiencies eased slightly in western Tasmania.
Rainfall received for the period was less than 50% of average for the affected areas in Western Australia, dropping to less than 30% of average in the Gascoyne and Central West, less than 30% of average for the Eyre Peninsula in South Australia, and less than 70% of average for southwestern Tasmania.
Product code: IDCKGRWAR0