Issued 4 June 2008

A dry autumn over much of Australia

May 2008 was Australia’s driest May on record. The dry May combined with relatively poor rainfall in March and April contributed to large parts of Australia experiencing rainfall deficiencies during autumn. Deficiencies at the yearly timescale highlight areas that have received little rainfall relief in recent months, with large areas of deficiencies through central and southern parts of Australia.

3-month rainfall deficiencies

For the 3-month period from March 2008 to May 2008, areas of serious to severe rainfall deficiencies covered large parts of Australia. In northern Australia this was indicative of an early end to the wet season, whilst southern Australia experienced a poor start to the southern wet season. Across the Murray-Darling Basin it was the fourth driest autumn on record.

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12-month rainfall deficiencies

Rainfall deficiencies for the 12-month period from June 2007 to May 2008 are evident over much of SA and southern NT and also in parts of southern WA, western Queensland and NSW, western and central Victoria and northern and eastern Tasmania. Over the 12-month period, much of eastern Australia had some benefit from above average rainfall associated with the 2007/08 La Niña event. In contrast, central areas of Australia have seen typically below average falls in recent months, with record-low falls evident for the period over a large area in southeastern parts of the NT and in small patches in central SA.

In some parts of southern Queensland and northeastern NSW, rainfall since the start of June has been sufficient to ease or remove the 3-month deficits. For areas covered by deficiencies over a 12-month period, average to above average winter falls are needed to ease deficiencies.

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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