Issued 2 May 2008
Long and short-term rainfall deficiencies persist
Short-term rainfall deficiencies expanded and intensified in central Australia as
a result of below average April rainfall. In addition, long-term rainfall deficiencies
at the two-year timescale have increased in most areas, except for southwest WA
which showed some easing of deficiencies.
See April rainfall pattern
7-month rainfall deficiencies
For the 7-month period from October 2007 to April 2008, an area of serious to severe rainfall deficiencies covered much of the southern half the Northern Territory and some adjacent areas in far western Queensland. An area of lowest on record to the east of Alice Springs has slightly increased. There were also some smaller patches of serious to severe deficiencies near Marree in South Australia.
24-month rainfall deficiencies
Rainfall deficiencies for the 24-month period from May 2006 to April 2008 are evident in southwest WA, Tasmania, southeast Queensland, northern SA and in a band stretching from the Bight coast of SA across much of Victoria and the western slopes and plains of southern NSW. The pattern is very similar to that observed at the end of March, but as April 2008 was drier than April 2006 in most areas, there was a slight increase of these two-year deficits. One exception was southwest WA which had a wetter April this year so the 24-month deficits eased somewhat. Record-low falls remain evident on the Eyre Peninsula in SA and in southwest WA where they are smaller in area. Compared with a month ago, record low falls at this time-scale expanded near Melbourne and in eastern and northern Tasmania.
The worst of the long-term deficiencies are likely to remain for some time. For example, above to very much above average rainfall (deciles 8-10) is needed in the rainfall deficient areas over the next six months just to elevate totals since May 2006 out of the lowest decile. Furthermore, due to the seasonally dry period in northern parts of Australia, short-term rainfall deficits in the NT are also likely to remain over the coming months.
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
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.
Product Code IDCKGD0AR0