Issued 3 September 2008
A dry autumn and winter over most of Australia
Rainfall in August 2008 had little effect in alleviating long and short term deficiencies over Australia. Below average rainfall over parts of eastern and southern Australia maintained short and long-term deficiencies in these areas, slightly worsening short-term deficiencies in southern Queensland into northern NSW, and in eastern Tasmania. Only minor relief to the rainfall deficits in the southern NT resulted from the above average August rainfall in the region, as the falls were generally light in absolute terms (August being a climatologically dry month).
6-month rainfall deficiencies
For the 6-month period from March 2008 to August 2008, areas of serious to severe rainfall deficiencies covered much of the southern interior of WA and adjoining areas of south-west NT; far western Queensland and the Barkly region of the NT; eastern Tasmania; and eastern Victoria, extending into the far south-east of NSW. There were also isolated areas of serious to severe rainfall deficiencies scattered through inland NSW, especially in the south and in the northwest, extending into southern inland Queensland. This latter area of deficiencies has slightly expanded in size due to below average rainfall in August. Below average rainfall in eastern Tasmania has caused a slight increase in the severity of deficiencies in this area, with an increased area of lowest on record. Small areas of lowest on record were also recorded in far-eastern Victoria and central WA. In northern Australia, deficiencies were generally indicative of an early end to the 2007/2008 wet season rains, whilst southern Australia has generally experienced a poor start to the southern wet season. While not reflected in an increase of the area of deficiencies, very much below average and lowest on record August rainfall over much of southwest WA has placed severe stress on cropping activities in the region.
15-month rainfall deficiencies
Rainfall deficiencies for the 15-month period from June 2007 to August 2008 remain evident over much of SA, including most of the agricultural districts, the southern NT and also in parts of southern WA, far western parts of both Queensland and NSW, western and central Victoria and northern and eastern Tasmania. Over the 15-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 from 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 2008 and a dry winter in 2007, has resulted in central and western parts of the state being in decile 1 for the 15-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 15-month period. The largest area of lowest on record rainfall for the period is seen in eastern Tasmania north of Hobart, with only a couple of small patches elsewhere. There were only marginal changes in the areas of longer-term deficiencies in August, with a small expansion of the area of severe deficiency in southcentral WA and northern SA, and a slight easing in western Victoria. Areas of long-term deficiencies generally 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.
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.