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

Fog forces RFDS flight carrying patients to Perth to land on Rottnest Island

11:39 EST

A Royal Flying Doctor Service aircraft has been forced to land on Rottnest Island with two patients on board because of the thick fog in Perth.

Frost, fog and freezing temperatures transform Canberra into winter wonderland

09:23 EST

As the mercury plunges Canberrans can be forgiven for wanting to stay indoors, but those brave enough to weather the elements have been greeted by a winter wonderland.

Federal Government unveils long-awaited plan for Australian agriculture

07:23 EST

The Federal Government has released the long awaited , which it had promised to deliver within 12 months of the 2013 election.