The monthly value of the Southern Oscillation Index (SOI) was +6.4 for April and +4.3 for May. According to the SOI Phase system, the SOI is in a ‘Consistently Positive’ phase.
Based on previous years when the SOI has been in a ‘Consistently Positive’ phase at the end of May, the probability of above-median rainfall for the next three-month period (June to August) is 40 to 60 per cent for much of Queensland.
Previous years with a ‘Consistently Positive’ SOI phase at the end of May include 1902, 1903, 1904, 1917, 1918, 1921, 1923, 1927, 1931, 1936, 1943, 1950, 1956, 1960, 1961, 1963, 1971, 1974, 1975, 1985, 1989, 2000 and 2010. The rainfall probabilities stated above are based on the 1900 to 1998 period and do not include 1989, 2000 and 2010.
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.
Users should note that 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, Innovation and the Arts and at www.bom.gov.au