Updated on 4 March 2015
Below-average rainfall increases deficiencies in eastern Australia
February 2015 was a particularly warm and drier-than-average month across Australia with national rainfall about half the long-term average and Australia's second-warmest daytime temperatures for February (see the monthly summary for details). Below-average February rainfall occurred across the Kimberley and adjacent parts of inland Western Australia, most of the Northern Territory, and most of Queensland except parts of the south and east coast. Rainfall was also below average for inland northeastern New South Wales, much of South Australia and adjacent border regions of New South Wales and Victoria, and for most of Tasmania.
Below-average rainfall has seen an increase in the area affected by deficiencies in southern South Australia, western Victoria, and coastal western Tasmania. Deficiencies at the multiyear timescale also increased in severity and extent across eastern Australia between inland Queensland south of the Gulf of Carpentaria and northern New South Wales inland of the Great Dividing Range.
8-month rainfall deficiencies
Compared to the previous Drought Statement, the spatial extent and severity of rainfall deficiencies for the 8-month period (July 2014 to February 2015) have increased across southern South Australia, western Victoria, and along the west coast of Tasmania. Deficiencies have again expanded in northwestern Victoria and adjacent parts of southern New South Wales. Deficiencies had decreased in January following above-average rainfall. The area experiencing severe or serious deficiencies (lowest 5% or lowest 10% of records) extends from the central West Coast district of South Australia, through southeastern South Australia and into western Victoria. Deficiencies are also present in a small area near Mildura and in northwestern Tasmania and a small area on the central west coast of Tasmania.
Parts of northwestern and central west coast Tasmania have been experiencing rainfall deficiencies across a range of timescales. 40% of Tasmania had rainfall in the lowest 10% of records for the 7-month period from August 2014 to February 2015, and 29% of the State experienced similar deficiencies for the 15-month period from December 2013 to February 2015.
Severe or serious deficiencies persist across the southern half of Queensland's Cape York Peninsula, although the focus of the area of deficiencies has shifted from the east towards central-to-western regions, and also remain in a small area near Townsville, but have decreased in extent in this area. Deficiencies also remain in Western Australia in parts of the Pilbara and northern Gascoyne within 400 km of the coast as well as in a smaller area of the southwestern Gascoyne.
29-month rainfall deficiencies
At the 29-month timescale (October 2012 to February 2015), rainfall deficiencies have also increased across central northern Queensland south of the Cape York Peninsula, extending through inland southern Queensland to northern New South Wales inland of the Great Dividing Range, and in the area covering western Victoria and adjacent southeastern South Australia. Severe and serious deficiencies are in place across these areas as well as in small areas of southwestern Queensland and adjacent parts of the southeastern Northern Territory and northeastern South Australia, pockets to the east of Mildura in southern New South Wales and around the northeast of Melbourne in Victoria, and in small parts of coastal western Tasmania. On the coast of the Gascoyne district in Western Australia deficiencies remain largely unchanged compared to the preceding 28-month period.
Long-term deficiencies in Queensland are largely the result of below-average rainfall over the 2013–14 and 2012–13 'summer' wet seasons (the northern wet season spans October–April). With only two months to go in the current wet season, rainfall would need to be above to very much above average to bring rainfall totals for October 2012 to April 2015 out of the lowest 10% of records for similar periods. For much of the affected region in western Victoria, southeastern South Australia, inland northern Queensland, and the region inland of the Great Dividing Range in northern New South Wales and southern Queensland the required totals would be in the highest 10% of records for March–April rainfall.
Soil moisture in the upper layer for the week ending 22 February had decreased, compared to the week ending 25 January, across most of eastern Australia. Areas of increased upper layer soil moisture in parts of the central east coast, eastern Victoria and adjacent southern New South Wales, eastern Tasmania, the far east of the Top End, and on the central west coast of Western Australia were largely associated with recent good falls on the east coast from ex-tropical cyclone Marcia, storms over the southeast, and moderate falls in parts of Western Australia. Soil moisture at the end of February was above to very much above average in these areas and in parts of the northeastern Cape York Peninsula and the area of Victoria between Melbourne and the central west coast.
Upper layer soil moisture was below to very much below average across the remaining majority of Western Australia and the Northern Territory; across most of South Australia; across most of Queensland away from the southern border and east coast, but extending into northeastern New South Wales inland of the Great Dividing Range; and across most of Tasmania's West Coast.
Lower layer soil moisture for the week ending 22 February had increased, compared to the week ending 25 January, across parts of eastern Australia. Lower layer soil moisture was above average for most of the eastern half of Western Australia, much of the Northern Territory, parts of Queensland's Gulf Country and central eastern Queensland, southern South Australia and parts of western New South Wales, and for an area covering East Gippsland in Victoria and far southeastern New South Wales. Soil moisture was below average in much of a 400 km wide strip along the west coast of Western Australia, parts of Queensland's north tropical coast and Central West District, a large area of southeastern Queensland and northeastern New South Wales, with patchy coverage then extending from northeastern New South Wales to parts of inland southern New South Wales, across most of Victoria except the far east and into southeast South Australia.
Product Code IDCKGD0AR0
The Weekly Rainfall Update describes rainfall over the previous week. It includes a map and a summary table of the highest weekly totals. A discussion of the impact of recent rains on rainfall deficiencies is also presented.
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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
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.