Seasonal Climate Outlook Message for July to October 2000

The bottom line

The average SOI over the previous 30 days has risen to -3.8. Based on the SOI, the probabilities of exceeding median rainfall during the total July to September period are little different from the 'normal' for this time of year in most of the eastern States of Australia, except for the Sunshine Coast and adjacent sub-coastal districts of Qld, central coastal and adjacent sub-coastal districts in NSW, where probabilities are 60-70%; and parts of northern Tasmania where the probabilities are 30-40%.

The full story

Based on the latest values and trends of the SOI, the probabilities of receiving above-median rainfall over the total July to September period are little different from the 'normal' for this time of year in most of the eastern States of Australia. Exceptions are the Sunshine Coast and adjacent sub-coastal districts of Qld, central coastal and adjacent sub-coastal districts in NSW, where probabilities are 60-70%; and parts of northern Tasmania where the probabilities are 30-40%.

The cooler-than-normal sea-surface temperatures that have been present in the central and eastern equatorial Pacific Ocean (since 1998) have receded. However, there are still patches of cool anomalies, particularly from the International Dateline to the central Pacific. The strength of the atmospheric circulation, typical of a La Niña pattern, has also weakened, but not to the same extent.

Most forecasts from experimental general circulation models are suggesting that neutral conditions will dominate at least until summer. Also some research suggests the sub-tropical ridge may again be further north than normal this winter, which tends to reduce winter rainfall from the Goondiwindi district through to the Central Highlands. As these indicators provide some cause for concern, regular monitoring of them and the SOI is highly recommended.

Frost risk this winter is detailed in a new DPI book: 'Frost Risk in Eastern Australia and the Influence of the Southern Oscillation' by Jacqui Willcocks and Roger Stone. There is a good probability that the frost season will finish 1-2 weeks earlier than normal for some towns in Queensland. Although the frost season may be shorter, the expected number of frosts is about the same as average, and the chance of getting at least one frost is similar to the average.

The next passage of the 30- to 50-Day Oscillation over Qld is expected about the third week in July.