SOI Message: 2nd August 2000
The average SOI over the previous 30 days has dropped to -4.6 . Based on the SOI, the probabilities of exceeding median rainfall during the total August to October period are little different from the 'normal' for this time of year in most of the eastern States of Australia, except for an area north and east of a line from Emerald to the Gulf of Carpentaria in Qld where probabilities are 20-40%; parts of inland NSW where probabilities are 30-40%; and the north-eastern corner of NSW where they are 50-70%.
Review of Climatic Forecasts and Information
Based on the latest values and trends of the SOI, the probabilities of receiving above-median rainfall over the total August to October period are little different from the 'normal' for this time of year in most of the eastern States of Australia.
However there are exceptions, and these include probabilities of receiving more than median rainfall of only 20-40% in the region north and east of a line from Emerald to the Gulf of Carpentaria, and parts of inland NSW where probabilities are 30-40%. Conversely, there are higher chances, 50-70%, in the north-eastern corner of NSW.
The cooler-than-normal sea-surface temperatures (SSTs) in the eastern equatorial Pacific Ocean, that characterised the 1998-2000 La Niña event, have continued to recede. Ocean temperatures off the Qld and northern Australian coastline are now slightly cooler than normal. However, SSTs off the southern half of Western Australia are significantly warmer than normal.
In terms of the future development of climatic patterns, most forecasts from experimental general circulation models are suggesting that neutral conditions will dominate until the end of the year. Interestingly, many of them suggest that sea -surface temperatures in the eastern equatorial Pacific Ocean may become slightly warmer than average, which may tend to reduce our spring/summer rainfall.
The current dry conditions over much of the south- eastern quarter of Qld have been partially due to the subtropical ridge being further north than normal. In the recent past similar years associated with a slightly negative SOI have included 1976, 1969, 1957, 1948, and 1939.
There is a good probability that the frost season will finish one to two weeks earlier than normal in some districts of Queensland. However, the expected number of frosts, and the chances of getting at least one frost, are about average.
The prospects for above-median pasture growth during the July-September period vary considerably across Qld, but are highest in parts of the region running from the northern Central Highlands to the Gulf of Carpentaria. However, pasture growth during this period is generally low, but can be valuable in terms of animal nutrition.
The next passage of the 30- to 50-Day Oscillation over Qld is expected about the second week in August.