Seasonal Climate Outlook Message for April to July 2017

The monthly value of the Southern Oscillation Index (SOI) was -2.2 for February and +3.8 for March. According to the SOI Phase system, the SOI is in a ‘Rapidly Rising’ phase.

A map showing the probability of above-median rainfall for the next three-month period (April to June) is available. This map is based on previous years from 1900 to 1998 which, like 2017, had a ‘Rapidly Rising’ phase of the SOI for March (i.e. 1901, 1902, 1903, 1907, 1908, 1913, 1914, 1927, 1931, 1935, 1937, 1947, 1952, 1959, 1960, 1964, 1969, 1970, 1973, 1986, 1988 and 1990). This map indicates a 40 to 60 per cent (near-normal) probability of above-median April to June 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.

Users should note that the SOI in autumn has low reliability as an indicator of rainfall. 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.

The Department of Science, Information Technology and Innovation (DSITI) also provides outlooks for the summer period (November to March). The outlooks for summer rainfall are based on conditions leading up to summer, including the state of the El Niño–Southern Oscillation (ENSO) phenomenon and factors which alter the impact of ENSO on Queensland rainfall (i.e. the more slowly changing extra-tropical sea surface temperature (SST) pattern in the Pacific Ocean). The DSITI Monthly Climate Statement for April 2017 is available.