SOI message 5th April 2000 The average SOI over the last 30 days was +9.0. Based on the SOI, the probabilities of exceeding median rainfall during the total April to June period are little different from the 'normal' for this time of year in most of the eastern States of Australia, except for coastal districts from St Lawrence in Qld to the Victorian border where the probabilities are higher at 60-80%.
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 April-June period are little different from the 'normal' for this time of year in most of the eastern States of Australia. Exceptions are coastal districts from St Lawrence in Qld to the Victorian border where the probabilities are higher at 60-80%; and the tip of Cape York Peninsula, parts of central and central-western Qld, and parts of north-eastern Tasmania where the probabilities are 60-70%.
The persistent 'cool' sea-surface temperature (SST) anomalies are slowly contracting, indicating that the La NiÂ¤a may be receding. This is also hinted at by other features such as the weakening of the strong easterly winds in the central Pacific Ocean associated with the La Nina.
Forecasts from most experimental general circulation models are currently suggesting that by mid-year the La Nina will have subsided and neutral conditions dominate. However, three climate models indicate the possible development of an El Nino, and 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 March-May period are 60-100% in much of north Qld; 0-10% in much of far North Qld (maximum pasture growth has already been achieved); and 0-40% in much of the south-eastern corner of Qld.
The next passage of the 30- to 50-Day Oscillation is expected about the end of the first week in April.