SOI message March 8th 2000
The average SOI over the last 30 days has fallen to +11.6 . Based on the SOI, the probabilities of exceeding median rainfall during the total March to May period are little different from the 'normal' for this time of year in most of the eastern States of Australia, 60-80% in much of north Qld, and 30-40 in most of the Burnett in Qld and parts of the northern inland cropping districts of NSW.
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 March-May period are little different from the 'normal' for this time of year in most of the eastern States of Australia. Exceptions are much of north Queensland (particularly Charters Towers-Bowen area) where the probabilities are 60-80%; parts of the south-eastern corner of NSW, south-western corner of Victoria and northern Tasmania where probabilities are 60-70%; most coastal and sub-coastal districts of Qld south of Bundaberg and parts of northern inland cropping districts of NSW where they are 30-40%.
The persistent 'cool' sea-surface temperature (SST) anomalies in the central and eastern equatorial Pacific Ocean, combined with 'warm' SST anomalies around northern and western Australia, suggest a mature La Nina pattern.
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 Qld. However, in less fertile areas of north Qld maximum pasture growth has already been achieved. Also in the south-eastern corner of Qld, the probabilities are only 0-40%.
The next passage of the 30- to 50-Day Oscillation is expected about the first week in April. It's 'shadow wave', which has tended to produce significant rainfall lately, will be due about mid-March.