Long Paddock

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:

Maps for the current three month period using the latest phase

Phase data updated 16:05pm, 24 May 2017, current for May 2017.

Chance of exceeding median rainfall in the period from May through July based on a rapidly falling SOI phase over March and April

Graphics in GIF format

Adobe PDF files, require Adobe Reader

Years in history with the same SOI phase over Mar–Apr

1884, 1888, 1909, 1912, 1914, 1922, 1924, 1944, 1945, 1947, 1952, 1965, 1967, 1969, 1976, 1993, 1994, 1995, 1997, 2004, 2005, 2012, 2016, 2017

Search Southern Oscillation Index (SOI) phases

The latest monthly data available is for April 2017 which was in a rapidly falling 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 April is calculated using March and April.

Find years when the SOI had the same phase as this date:

Find years when the SOI had this phase in this month:

Last updated 27 March 2012

Rainfall probabilities based on 'phases' of the SOI