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

Bureau of Meteorology staff begin strike action as 'last resort'

09:11 EST

Bureau of Meteorology (BoM) staff from across the country are set to begin a fortnight of industrial action following failed pay negotiations.

Wet system on track for ski resorts

13:15 EST

Make the most of the next few days on the slopes as the weather is set to take a turn for the worse.

Waves pound southern WA

10:36 EST

A deep low pressure system has sent a wintry blast over southwest WA and has also generated some massive waves along parts of the southern and southwestern coasts.