Seasonal Climate Outlook Message for December 2014 to March 2015

Commentary on rainfall probabilities based on 'phases' of the SOI

The monthly value of the Southern Oscillation Index (SOI) was -8.2 in October and -8.0 in November. According to the SOI Phase system, this places the SOI in a ‘Consistently Negative’ phase.

Based on previous years when the SOI has been in a ‘Consistently Negative’ phase at the end of November, the probability of above-median rainfall for the next three-month period (December to February) is 20 to 40 per cent for northern, central and much of south-eastern Queensland, with a 40 to 50 per cent probability of exceeding median December to February rainfall elsewhere. 

Previous years with a ‘Consistently Negative’ SOI phase at the end of November include 1900, 1901, 1911, 1913, 1914, 1919, 1925, 1939, 1940, 1941, 1944, 1951, 1963, 1965, 1972, 1977, 1982, 1991, 1992, 1994, 1997 and 2009. The rainfall probabilities stated above are based on the 1900 to 1998 period (that does not include 2009).

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.