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
10:10 CST
33°C
25°C
Possible thunderstorm
Weather News
BOM issues severe thunderstorm warning for NSW northern and central parts
11:02 EDT
Heavy rain, hail, and wind gusts of up to 90 kilometres an hour could impact parts of northern and central New South Wales today, the Bureau of Meteorology has warned, issuing a severe thunderstorm warning.
Severe storms set to lash NSW and QLD
14:13 EDT
Some of the worst thunderstorms of the season are set to lash parts of NSW and QLD, with a focus on the slopes and plains.
Blue skies for Taste of Sydney festival
09:50 EDT
Sydneysiders heading to the final day of the "Taste of Sydney" festival today are in for some cracking weather.
