Southern Oscillation Index
The Southern Oscillation Index (SOI) is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.
A strongly and consistently positive SOI pattern (e.g. consistently above about +6 over a two month period) is related to a high probability of above the long-term average (median) rainfall for many areas of Australia, especially areas of eastern Australia (including northern Tasmania) - La Niņa.
Conversely, a 'deep' and consistently negative SOI pattern (less than about minus 6 over a two month period, with little change over that period) is related to a high probability of below median rainfall for many areas of Australia at certain times of the year - El Niņo.
However, it is important to remember that the pattern of relationship between SOI and rainfall (and temperature) can vary depending on the particular season and region. Additionally, the change in SOI over a specified period can be as important in understanding relationships between SOI and rainfall as is the absolute value in SOI.
The Southwest Land Division is starting spring as winter ended, wet, helping grain crops recover after a drier-than-normal winter The Southwest Land Division dried out during August then picked up reasonable rain at the end of the month and is about to get spring off to a wet start, giving grain farmers some hope.
Broadacre crop growers in the Mallee region of South Australia and Victoria could be able to minimise losses from severe frost if they get more decent rain.
The latest bushfire outlook has warned of a heightened risk of fires across South Australia this summer.