SOI message 17th May 2000 The average SOI over the previous 30 days has dropped to +10.7 . Based on the SOI, the probabilities of exceeding median rainfall during the total May to July period are little different from the 'normal' for this time of year in most of the eastern States of Australia, except for parts of southern NSW, western Victoria and eastern Tasmania where the probabilities are 60-70%.
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 May-July period are little different from the 'normal' for this time of year in most of the eastern States of Australia. Exceptions are parts of southern NSW, western Victoria and eastern Tasmania where the probabilities are 60-70%.
The persistent `cool' sea-surface temperature (SST) anomalies are slowly contracting in the central and eastern equatorial Pacific Ocean, indicating a gradually receding La NiÂ¤a pattern. This is also hinted at by other features associated with the La NiÂ¤a, such as weakening of the strong easterly winds in the central Pacific.
Forecasts from most experimental general circulation models are currently suggesting that by mid-year the La NiÂ¤a event will be over and neutral conditions dominate. Sub-surface sea temperatures to the east of Australia are now significantly warmer than normal, in classic `pre-El Nino' mode. In addition, some early research work suggests the sub-tropical ridge may again be further north than normal this winter which may tend 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 during the autumn `predictability gap' is recommended.
Combining the rainfall outlook with current soil water and pasture condition, the probabilities of above- median pasture growth during the total May-July period are 60-100% in much of Qld; 0-40% in much of far North Qld (maximum pasture growth has already been achieved); and 0-40% in eastern areas of southern Qld due to current poor soil moisture.
The next passage of the 30- to 50-Day Oscillation over Queensland is expected about the at the end of May.