Southern Oscillation Index
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.
Now Temperature
At Darwin Ap
08:40 CST
26°C
36°C
Sunny
Weather News
Victoria weather: Wangaratta residents given all-clear to return home after levee leak
10:02 EDT
Concerns about a leaking levee at Wangaratta, in northern Victoria, have eased overnight, with emergency officials saying residents can return to their homes today.
SA weather: Storm damage at Linear Park trail worst Adelaide council has seen
08:40 EDT
A trail of destruction left along the River Torrens and Linear Park trail after South Australia's wild storm will take weeks to clean up and repair, the Charles Sturt Council says.
Wangaratta residents face flood risk from levee as Victorians warned of wild weekend weather
07:31 EDT
A levee at risk of breaching has prompted an emergency evacuation warning for about 350 residents in Wangaratta, in Victoria's north-east.
