Issued 7 October 2015
A dry September sees deficiencies persist or slightly increase
September rainfall was below average for most of Australia. Below-average rainfall was observed in Tasmania and a broad swathe of the mainland extending across agricultural South Australia, nearly all of Victoria, much of New South Wales west of the ranges, through southern and western Queensland, the majority of the Northern Territory, and most of Western Australia. September was amongst the ten driest Septembers on record for Victoria, Tasmania and Western Australia.
Following a generally very dry month, deficiencies have increased slightly in both severity and extent at all monitored timescales when compared to the last Drought Statement. Increases were most notable in southwest Western Australia at the shorter 5-month and 15-month timescales (May to September 2015, and July 2014 to September 2015 respectively), while increases in eastern Australia in Queensland, Victoria and adjacent southeast South Australia were generally similar across all three monitored periods (including the 36-month October 2012 to September 2015 period).
Serious or severe rainfall deficiencies have been observed in parts of southeast Australia for various medium-term periods since late 2013, and for longer-term deficiencies for various periods to around 2 years duration. For eastern Australia more generally, rainfall has been very much below average for large areas for periods of about 3 years' duration, in Queensland largely as a result of poor wet-season rainfall in successive years. Long-term deficiencies also exist in eastern Australia 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.
5-month rainfall deficiencies
Below-average September rain has seen rainfall deficiencies increase in southwest Western Australia, parts of southeast South Australia and western to central Victoria, as well as in parts of coastal eastern Tasmania at the 5-month timescale (May to September 2015). Severe deficiencies (lowest 5% of historical records for similar periods) persist over most of southwest Western Australia (the area southwest of a line between Jurien Bay and Bremer Bay).
Pockets of serious rainfall deficiencies (lowest 10% of historical records) are in place in far southeastern South Australia and an adjacent part of the Wimmera in Victoria, central Victoria, and eastern Tasmania. Much of Victoria and southeastern South Australia have received below-average rainfall for the five-month period and for the cool season to date.
Deficiencies have also increased in some parts of northern Australia, although September is typically the last month of the northern dry season. Rainfall is typically low over most of northern Australia between May and September. Areas of deficiencies persist in parts of the north of Western Australia and adjacent to Queensland's East Central Coast.
15-month rainfall deficiencies
For the 15 months July 2014 to September 2015, deficiencies have generally increased in extent or severity in all affected regions.
Severe or serious deficiencies (lowest 5% or lowest 10% of historical records) persist in an area extending from northwestern South Australia, along the coast of South Australia, and across most of Victoria except Gippsland and parts of the Alps. Rainfall for the period remains lowest-on-record for an area spanning southeastern South Australia and adjacent parts of western Victoria. Serious or severe deficiencies also persist in western and northern Tasmania. Severe deficiencies (lowest 5% of historical records) affect 47% of Victoria—a value that has not been exceeded for a 15-month July–September period since 1944–45.
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).
Deficiencies also persist along the west coast of southwest Western Australia, and 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.
36-month rainfall deficiencies
At the 36-month timescale (October 2012 to September 2015), rainfall deficiencies have increased slightly in extent or severity in all affected regions.
Severe or serious deficiencies (lowest 5% or lowest 10% of historical records) persist 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 in an area spanning southeast South Australia and much of western to central Victoria, pockets along the west and east coast of Tasmania, and parts of the central South West Land Division in Western Australia along a line roughly from Jurien Bay to Albany.
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 27 September had decreased across nearly all of Australia compared to the week ending 30 August.
Upper layer soil moisture was below to very much below average in the west of Western Australia, across most of southern Australia, nearly all of Tasmania, and in much of New South Wales and large parts of Queensland. Upper layer soil moisture was above average in some areas along the coast between East Gippsland in Victoria and southeastern Queensland.
Lower-layer soil moisture for the week ending 27 September was generally similar to that for the week ending 30 August, with slight decreases in much of southern Australia and parts of inland Queensland.
Lower-layer soil moisture was above average for a large area of Western Australia between the northwest and southeast, the central Northern Territory, far eastern Victoria and southeastern New South Wales, parts of western New South Wales, and parts of South Australia but not the southeast. Soil moisture was below average in western parts 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 parts of eastern Tasmania.