The average SOI over the previous 30 days has is now +11.2. For the first time in about two years rainfall probability values have risen to comparatively high levels for most of Queensland. The probability of exceeding the long-term median is now 60% to 80% for many regions in Queensland but with the notable exception of the southern Darling Downs and southern border districts where they remain comparatively low at about 50%.
Review of Climate Forecasts and Information As mentioned in previous forecast releases, the dry conditions experienced over much of Queensland, and especially over southern Queensland, has been due to the unusually more northern position than usual of the sub-tropical ridge of high pressure this year. This pattern would not normally be expected to persist beyond spring, suggesting some easing of the dry conditions are possible within the next 1 or 2 months.
SOI patterns and 'phases' The latest SOI 'phase' analysis suggests reasonably high probability values for many areas of Queensland for the October/December period this year. For example, the probability of exceeding the long-term median rainfall for most of eastern Qld is between 60% and 80%. Similarly, the probability of exceeding the long-term median for some inland parts of central and southern NSW is also 60% to 70%. It should be remembered that a 70% probability of exceeding the long-term median for a location also means there is a 30% probability of not exceeding the median for that location. These probability values are simply statements of fact referring to the history of rainfall events for particular locations over the past 100 years.
However, over far southern Queensland (Including the southern Darling Downs) and northern NSW the probability of exceeding the long-term median for the period between October and December remains comparatively low at close to 50%.
Sea-surface temperatures. Sea-surface temperatures in the Pacific and Indian Oceans are generally close to 'average' at the moment, although there are patches of cooler than normal temperature in the far eastern equatorial Pacific. Some general circulation models are suggesting or hinting at the potential for warming in the eastern Pacific over the next 6-9 months. We will keep a close watch on these developments to determine any potential for El Niño development or otherwise in 2001. We suggest close monitoring of sea-surface temperature patterns over the next 6 months.
Pasture Growth forecasts. The probabilities of obtaining median pasture growth or better during the October to December period are 'above-average' over most of Qld but with the notable exception of parts of the south-east of the State. In the south-east of the State the probabilities of exceeding median pasture growth are down to 10% to 30%. 30-50 Day Oscillation. The next passage of the 30- to 50-Day Oscillation over Qld is expected about the second week in October.