Updated on 8 January 2015
Some relief on the east coast, rainfall deficiencies increase in western Victoria and southeast South Australia
December rainfall was below to very much below average for the Cape York Peninsula, large areas along and inland of the western coast of Western Australia, southern South Australia and western to central Victoria and smaller areas in the western Top End in the Northern Territory and southwest Tasmania. Monthly rainfall was in the lowest ten per cent of records (decile 1) for much of the Cape York Peninsula, and in pockets along the western coastline of Western Australia (however rainfall is typically low in in this region at this time of year). While rainfall in December has alleviated rainfall deficiencies in some parts of the east, rainfall has been below average across large parts of eastern Australia for most of 2014 and below-average rainfall in the past month has increased deficiencies in western Victoria and southeast South Australia at both shorter and longer timescales.
6-month rainfall deficiencies
For the 6-month period (July–December 2014), above-average December rainfall has significantly moderated short-term deficiencies across the Top End, eastern Northern Territory, central Australia and western Queensland. Serious and severe deficiencies (lowest 10% to lowest 5% of records) remain across most of the Cape York Peninsula, increasing in some areas. Small pockets of deficiencies also remain in the western Top End and northeastern South Australia.
Above to very-much-above-average rainfall along the east coast of New South Wales during December has alleviated deficiencies along and inland of the Great Dividing Range, although deficiencies remain for parts of southern New South Wales, the western half of Victoria, southeastern and agricultural regions of South Australia and a small area of northwestern Tasmania. The area affected by severe deficiencies (lowest 5% of records) in western Victoria and southeast South Australia has increased.
13-month rainfall deficiencies
The effect of recent rainfall has been less pronounced at the 13-month timescale (December 2013 – December 2014). Deficiencies have been removed from parts of southeastern Queensland and northeastern New South Wales, but areas of deficiencies still remain in some areas. Small pockets of serious deficiencies also remain in inland northern Queensland. Deficiencies have increased in western Victoria and adjacent southeastern South Australia. Deficiencies also persist in parts of Tasmania's east coast, northwest and west coast.
27-month rainfall deficiencies
At the 27-month (October 2012 – December 2014) timescale, serious and severe rainfall deficiencies persist across much of Queensland away from the coast, extending into inland northeastern New South Wales, the southeast of the Northern Territory and northeast South Australia. Rainfall in the past month (December 2014) has alleviated deficiencies in some areas around the Central Highlands District of Queensland but little change has been seen in other areas.
The areas of serious and severe deficiencies have slightly increased since last month in the western half of Victoria and adjacent southeastern South Australia. Nearly the entire western half of Victoria is covered by deficiencies, excepting along the coast and the northern border. Deficiencies also persist in an area of the southern coastal Gascoyne around Shark Bay in Western Australia.
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). While December has brought above-average rainfall to much of northern Australia except the Cape York Peninsula, rainfall in the remainder of the northern wet season will also have to be well above average to lift the remainder of Queensland out of deficiency, i.e. above the tenth percentile for this time period.
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.
The current drought in Queensland is comparable to the 2002–2003 drought, which was perhaps more severe in terms of rainfall deficiencies that occurred at times over a very large area. Historical data shows that the current drought is perhaps a one in ten or twenty year event over a significant part of inland eastern Australia (see for example the 24-month deciles map for 2013–2014), but very severe in some places. For some locations in central Queensland the present deficiencies are the most severe on record, and have been accompanied by record high temperatures. See: 24-month maximum temperature deciles map for 2013–2014.
Following above-average rainfall for much of tropical northern Australia, upper layer weekly soil moisture for the week ending 28 December was very much above average across the Kimberley and much of the Northern Territory, southern Queensland, northeastern and eastern New South Wales as well as along much of the southern coast of Western Australia. Soil moisture was below average for the Cape York Peninsula and parts of Queensland's north coast and inland north, parts of the Top End, along much of the west coast of Western Australia and also below average in a broad area covering much of eastern South Australia, western New South Wales, Victoria, except East Gippsland, and Tasmania.
Compared to last month, lower layer weekly soil moisture for the week ending 28 December remains similar across Western Australia, has increased in the Kimberley and central Northern Territory and parts of central eastern Queensland. Lower layer soil moisture is below average along much of the west coast and adjacent hinterland of Western Australia, the central Top End, inland northern Queensland, a large area of southeastern Queensland and northeastern New South Wales, parts of southern New South Wales, most of Victoria, except the far east, and southeastern South Australia. Soil moisture is also below average for areas of northwestern, central and eastern Tasmania.