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 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.
The last few nights have brought a spectacular light show to Tasmania, southern Victoria and New Zealand, with the potential for more to come over the next few weeks.
Grantham floods inquiry: Denis Wagner considers legal options after report finds quarry impact 'insignificant'
The former owner of the Grantham quarry is considering his legal options after an inquiry found it did not contribute to the town's deadly 2011 floods.
The Grantham Floods Commission of Inquiry has ruled the Grantham quarry played little role in the deadly 2011 flood and its owners were unjustly blamed.