Issued 4 September 2015
Deficiencies increase to cover much of Victoria, generally little change elsewhere
August rainfall was below average for a most of Victoria and for southeast South Australia, northern Tasmania, and west coast Western Australia. Rainfall was also below average for parts of northern Australia in Queensland and Western Australia, but August forms part of the dry season for northern Australia and monthly rainfall is typically very low for the north away from the east coast of Queensland. Monthly rainfall was above average for much of the south of Western Australia except the southwest, moderating short-term (May 2015 to August 2015) rainfall deficiencies in some areas.
Compared to the last Drought Statement, deficiencies decreased in parts of coastal central and western South Australia at the 14-month timescale (July 2014 to August 2015), but have increased in severity in southeast South Australia and western to central Victoria at both the 14-month and 35-month (October 2012 to August 2015) timescales, with pockets of deficiencies emerging at the 4-month timescale. Serious or severe rainfall deficiencies have been observed in parts of the southeast for various medium-term periods since late 2013, and for longer-term deficiencies for various periods to around 2 years duration. Rainfall has been very much below average for large areas of eastern Australia for periods of about 3 years' duration and more also over the 17 years since 1998.
The southern wet season, which spans April to November, continues to track below average rainfall for the season so far in central to western Victoria, southeastern South Australia, Tasmania, and across most of the South West Land Division in Western Australia.
4-month rainfall deficiencies
Above-average August rain fell across much of the south of Western Australia, although along the west coast rainfall was below average for the month. Consequentially, deficiencies have decreased in some eastern parts of the South West Land Division and adjacent areas further inland, but severe deficiencies (lowest 5% of historical records for similar periods) persist over most of the southwest (the area west of a line between Jurien Bay and Bremer Bay).
Pockets of serious rainfall deficiencies (lowest 10% of historical records) have also emerged in parts of western Victoria following a drier-than-average August. Much of Victoria and southeastern South Australia have received below-average rainfall for the four-month period and for the cool season to date.
Areas of deficiencies persist in parts of northern Australia, although this period corresponds to the dry season there. Rainfall is typically low over most of northern Australia between May and September.
14-month rainfall deficiencies
For the 14 months July 2014 to August 2015, severe or serious deficiencies (lowest 5% or lowest 10% of historical records) persist with little change in areas of northern Queensland extending across the southern and central Cape York Peninsula, roughly from Kowanyama to Townsville, along the southern coast of the Gulf of Carpentaria, and in an area of inland central Queensland near Longreach.
A substantial area of lowest-on-record rainfall also persists, and has increased in spatial extent, in southeastern South Australia and western Victoria. Serious or severe deficiencies have increased in western to central Victoria. Severe deficiencies (lowest 5% of historical records) now affect nearly 50% of Victoria—a value that has not been exceed for the July–August period since 1944–45. In contrast, deficiencies have been moderated by recent rainfall in parts of southern South Australia between Ceduna and the Yorke Peninsula.
Much of southeastern Australia has seen below-average April–November rainfall during three of the last four years, with monthly rainfall also below average from August last year for much of this region (apart from well-above-average January rainfall, and above-average March and May rainfall in Tasmania). Serious deficiencies also remain in parts of northern and western Tasmania, northwestern South Australia, and along the west coast of southwest Western Australia.
35-month rainfall deficiencies
At the 35-month timescale (October 2012 to August 2015), rainfall deficiencies have increased slightly in both extent and severity in western to central Victoria and southeastern South Australia. Deficiencies have also increased in parts of the central South West Land Division in Western Australia, now reaching along a line roughly from Jurien Bay to Albany, and persist in pockets of southeastern and western Tasmania.
Serious and severe deficiencies persist with little change in Queensland, extending from the base of the Cape York Peninsula, through central Queensland into parts of central southern Queensland and northern New South Wales to the west of the Great Dividing Range.
Deficiencies also persist at a range of even longer timescales, with most of eastern Australia having received below-average rainfall following the conclusion of the 2010–12 La Niña events.
Soil moisture in the upper layer for the week ending 30 August had increased across southern Australia in a band across the southern coast of Western Australia, through southern South Australia and most of New South Wales, to eastern Victoria compared to the week ending 26 July, and also increased in the central Northern Territory. Soil moisture in these areas was very much above average at the end of August and was also above average in parts of inland southeastern Queensland and the west of Cape York.
Upper layer soil moisture decreased, compared to a month ago, in the Pilbara and Gascoyne in Western Australia, in southeastern South Australia and western to central Victoria, Tasmania, and parts of northern Australia. Soil moisture was below average for much of southwest Western Australia, the Victoria River district of the Northern Territory and areas of the southern Top End, parts of central and southern Queensland, along the east coast of Queensland and New South Wales, and very much below average between southeast South Australia and central Victoria, and across the western half and central east of Tasmania.
Lower-layer soil moisture for the week ending 30 August was generally similar to that for the week ending 26 July, although having decreased slightly in southeastern South Australia and western Victoria as well as eastern Tasmania. Compared to a month ago soil moisture increased slightly in parts of the South West Land Division of Western Australia, but remained below average.
Lower-layer soil moisture was above average for most of the northwest and interior of Western Australia, the central Northern Territory, eastern Victoria, western New South Wales, and parts of South Australia but not the southeast. Soil moisture was below average in most of the northern half of the South West Land Division in Western Australia, and also for areas of coastal northern Queensland, around the Gulf coast, parts of the Top End, some areas between central Queensland and northern New South Wales, much of central to western Victoria and southeastern South Australia, and for part of eastern Tasmania.