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
12:10 CST
32°C
24°C
Possible thunderstorm
Weather News
Electric skies over WA's Goldfields and Southern Interior
11:11 EST
A low and trough is delivering plenty of lightning to southern central WA to finish off the Easter long weekend.
Wet start to April after a record-breaking March for Lord Howe Island
12:32 EST
Following a very wet March, Lord Howe Island received another good douse of rain during the first week of April 2017.
Sun-soaked Easter Sunday for much of Australia
11:17 EST
Now that the sun has risen on Easter Sunday, celebrations are in full swing, with only a few showers in the north and west dampening the mood.
