Seasonal Climate Outlook Message for August to November 2000
The bottom line
The average SOI over the previous 30 days has increased to +4.0 . 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%.
The full story
Based on the latest values and trends of the SOI, the probabilities of receiving median rainfall or better 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 exceeding 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.
Similar years in the past (associated with a slightly negative SOI) have included 1976, 1969, 1957, 1948 and 1939.
The cooler-than-normal sea-surface temperatures (SSTs) in the eastern equatorial Pacific Ocean, that characterised the 1998-2000 La Niña event, have receded. 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 the best experimental general circulation models are suggesting that neutral conditions will dominate until about January. 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 Qld have been partially due to the subtropical ridge being further north than normal.
There is a high 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.
Current soil moisture levels are low over much of Qld. When this is combined with the seasonal rainfall outlook, the probabilities of obtaining median pasture growth or better during the August-October period are only 10-40% over much of the State. 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 first week in September.
