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

Trans-Tasman temperature contrast

15:28 EDT

New Zealand is experiencing an unseasonably cool summer, whilst parts of eastern Australia endure their hottest start to the year on record.

Kimberley cattle country soaked by January rains in great start to season

10:39 EDT

Cattle stations in the Kimberley region of Western Australia have had an extremely wet start to 2017.

Forbes Creek couple look to rebuild dream home one year after freak 'mini tornado'

06:51 EDT

On a windy night late last January, Jan and Geoff McKergow's dream home was torn to rubble.