La Niña to exit stage left? by Dr Roger Stone Queensland Centre for Climate Applications
GroundCover™ Issue: 30
As previously suggested, the La Niña pattern in the Pacific Ocean has now reached maturity. From March onwards rainfall probability patterns associated with the current Southern Oscillation Index (SOI) pattern tend to become rather patchy over most of Australia.
We are now entering a particularly critical time of the year. This is the period when the Pacific Ocean tends to review its position. SOI patterns established at the end of May may persist for about the next 12 months.
The rainfall probability map for the March to May period shows highest rainfall probabilities over northern Australia with some similar but patchy patterns over the central NSW coast and in SE South Australia.
Although the SOI is still quite high, notice that parts of southern inland Queensland around the Burnett and the northern Darling Downs now have probabilities dropping to 30 per cent of exceeding median rainfall.
Northern Australia generally and especially north-east Queensland have higher rainfall probabilities in the next three months, whereas the rest of Australia and especially parts of south-east Queensland have reduced rainfall probabilities.
It will be very important to update this information as we proceed through the autumn period and head for the winter cropping season. The SOI and sea-surface temperature patterns tend to be rather fickle through the autumn months. Most climate forecasting systems tend to perform rather poorly through this period.
However, at this stage, the more sophisticated mathematical models are suggesting the La Niña pattern will wane by the end of autumn 2000.