Issued 3 july 2008>

Rainfall deficiencies persist over much of Australia

After Australia’s driest May on record, June 2008 brought some relief, especially to northern NSW, southern Queensland and the central NT. However, large parts of Australia experienced average to below average rainfall, which was not enough to relieve short- or long-term deficiencies. Deficiencies at the 13-month timescale highlight areas that received little rainfall relief from the previous year's La Niña event, with large areas of deficiencies through central and southern parts of Australia.

4-month rainfall deficiencies

For the 4-month period from March 2008 to June 2008, areas of serious to severe rainfall deficiencies covered large parts of central and southeastern Queensland, much of Victoria, eastern Tasmania, western SA, the southwestern corner of the NT and a large area in central parts of southern WA. In northern Australia this was indicative of an early end to the wet season, whilst southern Australia has generally experienced a poor start to the southern wet season. Some southern parts of the NT and Queensland into northeastern SA and northwestern NSW have had short-term deficiencies ease, due to a rainfall event in the area at the start of June.

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13-month rainfall deficiencies

Rainfall deficiencies for the 13-month period from June 2007 to June 2008 remain evident over much of SA and southern NT and also in parts of southern WA, western parts of both Queensland and NSW, western and central Victoria and northern and eastern Tasmania. Over the 13-month period, much of eastern Australia had some benefit from above average rainfall associated with the 2007/08 La Niña event. However, this was mainly over late 2007 to around February 2008, with typically below average rainfall since. Although Victoria received average to above average falls over summer, the combination of very much below average rainfall since the start of autumn and a dry winter in 2007, has resulted in central and western parts of the state being in decile 1 for the 13-month period. Tasmania, central areas of Australia and some southern parts of WA, which did not receive as much relief from the La Niña event, have also seen typically below average falls in recent months, leading to a continuation of rainfall deficiencies over the 13-month period. Patches of lowest on record rainfall for the period are seen in eastern Tasmania around Hobart, southern SA to the east of Ceduna, the NT to the east of Alice Springs and in some small patches in WA to the northeast of Esperance.

The deficiencies discussed above have occurred against a backdrop of decade-long rainfall deficits and record high temperatures that have severely stressed water supplies in the east and southwest of the country. Several years of above average rainfall are required to remove the very long-term deficits. The combination of record heat and widespread drought during the past five to ten years over large parts of southern and eastern Australia is without historical precedent and is, at least partly, a result of climate change. For more information go to a Special Climate Statement on the six years of widespread drought in southern and eastern Australia, November 2001 to October 2007

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Definitions

Lowest on record - lowest in the historical analysis, which runs from 1900.
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.

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