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 Niña.

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 Niño.

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

Australian Open: Heat policy needs to be looked at, Djokovic says, but Federer maintains his cool

10:14 EDT

The hottest topic of the Australian Open is once again the heat after a day in which Melbourne sweltered and players just about got roasted on court.

Melbourne set to hit 42C as Victoria warned of severe fire threat

10:08 EDT

Melburnians — and the world's best tennis players — are bracing for a 42C stinker today, as energy authorities flag the possibility of curtailing some industrial power users and firefighters prepare for severe risks.

Parts of Australia to pass 40C today as others brace for a hot weekend

09:57 EDT

Very hot and dry conditions have been forecast across the country today and over the weekend, fuelling warnings of extreme fire danger in some states.