Fairfax Media Network

Agriculture Weather


Southern Oscillation Index

  • location
  • Aus

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.

Southern Oscillation Index

SOI

Nino3.4 Index

Nino3.4
Display Your Local Weather

Weather News

Heatwave to scorch Queensland 'well into next week', BOM warns

18:22 EDT

Temperatures will remain above 40 degrees Celsius in parts of central and southern Queensland until at least Wednesday next week, the Bureau of Meterology (BOM) warns.

Do you know the signs of heat stress?

17:26 EDT

Hot weather can take a serious toll on our health.

Extreme heatwave sparks total fire ban in NSW

16:01 EDT

The sort of temperatures that see roads melt and cold taps flowing with boiling water are set to scorch Sydney and northern New South Wales over the next few days with the weather bureau officially forecasting a rare "extreme heatwave".