Rainfall probabilities based on 'phases' of the Southern Oscillation Index
Recent trends in the Southern Oscillation Index (SOI) can be used to calculate more accurately the probabilities of receiving particular amounts of rainfall at a particular location; over the next few months. The phases of the SOI were defined by Dr Roger Stone then of QDPI, who used a statistical technique (cluster analysis) to group all sequential two-month pairs of the SOI (from 1882 to 1991) into five clusters (see legend below & help on use of trends in the SOI).
By using this information we have constructed maps of future rainfall probability.
Reference for the SOI Phase system: Stone, R.C., Hammer, G.L and Marcussen, T. (1996) Prediction of global rainfall probabilities using phases of the Southern Oscillation Index. Nature, 384, 252-255.
Maps for the all five SOI phases:
- Consistently negative (phase 1)
- Consistently positive (phase 2)
- Rapidly falling (phase 3)
- Rapidly rising (phase 4)
- Consistently near zero (phase 5)
Maps for the current three month period using the latest phase
Phase data updated 17:10pm, 26 Oct 2016, current for October 2016.
Chance of exceeding median rainfall in the period from October through December based on a rapidly rising SOI phase over August and September
Graphics in GIF format
- Australia - opens in new window (GIF, 45kB)
- Queensland - opens in new window (GIF, 43kB)
- World - opens in new window (GIF, 71kB)
Adobe PDF files, require Adobe Reader
Years in history with the same SOI phase over Aug–Sep
1889, 1890, 1899, 1903, 1908, 1921, 1922, 1926, 1935, 1936, 1949, 1970, 1979, 1983, 1989, 2001, 2005, 2009, 2011, 2012, 2016
Search Southern Oscillation Index (SOI) phases
The latest monthly data available is for September 2016 which was in a rapidly rising phase. The searches below default to the latest available month and phase.
Note: the phase for the selected month is calculated using that month and the preceding month, e.g. the phase for September is calculated using August and September.
Last updated 27 March 2012