Long Paddock

Commentary on rainfall probabilities based on phases of the SOI

Previous commentary

Seasonal climate outlook message for September to November 2016

The monthly value of the Southern Oscillation Index (SOI) was +3.70 for July and +4.67 for August. According to the SOI Phase system, the SOI is in a ‘Consistently Near-Zero’ phase.

A map showing the probability of above-median rainfall for the next three-month period (September to November) is available. This map is based on previous years from 1900 to 1998 which, like 2016, had a Consistently Near-Zero SOI over July and August (i.e. 1903, 1907, 1912, 1913, 1922, 1926, 1927, 1929, 1930, 1931, 1932, 1933, 1935, 1939, 1948, 1949, 1952, 1959, 1961, 1963, 1968, 1969, 1978, 1980, 1984, 1990, 1992, 1995, 1999, 2001, 2003, 2004, 2009, 2012 and 2013). This map indicates a 40 to 60 per cent (near-normal) probability of above-median September to November rainfall for most of Queensland.

When using a climate outlook it should be remembered that the probability, or per cent chance, of something occurring is just that – a probability. For example, if there is a 70 per cent probability of above-median rainfall, then there is also a 30 per cent chance of below-median rainfall. It does not mean that rainfall will be 70 per cent more than the median.

Furthermore, while climate outlook schemes cannot provide outlooks with absolute certainty, users who follow a skilful scheme should benefit from doing so in the long-term. Thus, users should consider the historical track record of any scheme, and such information is becoming increasingly available.

Further seasonal climate outlook information for Queensland is available in the Monthly Climate Statement produced by the Department of Science, Information Technology and Innovation.

Last updated 18 March 2011

Seasonal climate outlook