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
10:40 CST
32°C
25°C
Possible thunderstorm
Weather News
BOM warning as Cyclone Debbie intensifies; Queensland emergency services prepare for worst
11:57 EDT
Thousands of north Queenslanders are being evacuated as Cyclone Debbie bears down on the coast, bringing winds of up to 230 kilometres per hour and possibly a four-metre storm surge.
Cyclone Debbie: A quick guide for residents
11:53 EDT
Tropical Cyclone Debbie is just hours from reaching the northern Queensland coast.
Tropical Cyclone Debbie: Queenslanders preparing for worst cyclone since Yasi
11:26 EDT
As Tropical Cyclone Debbie strengthens off the coast near Townsville in north Queensland, residents are being warned to prepare for the worst storm to hit the state since Cyclone Yasi in 2011.
