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
13:40 CST
30°C
24°C
Possible thunderstorm
Weather News
NSW weather: Residents in catastrophic bushfire areas told to leave, emergency warning for Leadville
14:47 EDT
The New South Wales Rural Fire Service (RFS) says people who live in bushland areas with catastrophic fire conditions need to leave their homes as blazes can become uncontrollable in minutes.
Live coverage: Heatwave drags on across NSW and Queensland
14:30 EDT
New South Wales and southern Queensland are experiencing another day of extreme conditions, with temperatures exceeding 40 degrees Celsius in some parts.
WA floods: Man's body found near Esperance, fears for three others at Lake King
13:54 EDT
WA Police have found the body of a man whose car was washed away after trying to cross a flooded road near the town of Esperance on Saturday.