Issued 2 June 2004

Autumn rains fail; severe deficiencies widespread in the southeast

The Bureau of Meteorology announced today that autumn rains failed across large areas of the winter cropping regions of southeast and southern Australia, as well as an area in the southwest of WA. In addition, long-term (since mid-2002) rainfall deficiencies persist over the southeast of the mainland. The recent low falls in the southeast of the country have added significance in that this general region has experienced below normal rainfall for most of the past 8 years.

5-month rainfall deficiencies

For the 5-month period from January to May, severe rainfall deficiencies have emerged over the southern half of NSW, the ACT, northern and central Victoria and southeast and south-central SA, while serious deficiencies are evident in a few small patches in the southwest of WA. Patches of lowest on record falls have occurred near the Murray River between Swan Hill and Renmark, as well as in the Victorian Mallee and adjacent Murray Lands in South Australia. It is also worth noting that serious deficiencies for the March to May period exist in southwest WA in an area roughly bounded by Wandering, Jerramungup, Albany and Denmark.

The impact of the low rainfall has been intensified by very much above average (highest 10%) or record high maximum temperatures since the start of the year. For example, averaged over the Murray Darling Basin, the mean maximum temperature for the year to date is about 1.5 degrees above average, some 0.2 degrees above the previous record set in 2001.

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23-month rainfall deficiencies

For the 23-month period from July 2002 to May 2004, rainfall deficiencies still persist in the southeast of the mainland, in an area, which although smaller than that affected by 5-month deficiencies, largely overlaps with it. However, this longer period affects areas further south including Gippsland, and the Central district surrounding Melbourne. A large part of the NSW Southern Tablelands has had record low falls for the 23-month July to May period. In WA, long-term rainfall deficiencies are evident in a relatively small patch near Exmouth and Onslow, as well as in a very small area near Busselton.

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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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