Monthly climate statement for November 2017

The Department of Science, Information Technology and Innovation (DSITI) monitors sea-surface temperature (SST) anomalies in key regions of the Pacific Ocean over autumn, winter and spring and provides objective outlooks for summer (November to March) rainfall on this basis. The Science Division of DSITI considers that the probability of exceeding median summer rainfall is slightly higher than normal for much of Queensland. With respect to extreme conditions, for most of Queensland the probability of a dry summer (< decile 3 rainfall) is lower than normal and for most of Queensland the probability of a wet summer (> decile 7 rainfall) is near-normal. Read more (PDF, 202K, last updated 03:07PM, 10 November 2017)*

Rainfall in Queensland over spring and summer is strongly influenced by the El Niño-Southern Oscillation (ENSO) — a coupled atmospheric and oceanic phenomenon which is strongly persistent at seasonal timescales. The key oceanic indicator of ENSO is the SST anomaly in the Niño 3.4 region of the Pacific Ocean. The October SST anomaly was -0.5°C, a monthly value which is on the threshold between ENSO-neutral and La Niña classifications. The Southern Oscillation Index (SOI) is the key atmospheric indicator of ENSO. The average value of the SOI for August to October was +6.8, a three-month value which, likewise, is on the threshold between ENSO-neutral and La Niña classifications.

DSITI provides outlooks for summer rainfall based on an objective analysis of Pacific Ocean SSTs. This final analysis for summer indicates a slightly higher than normal probability of exceeding median rainfall across much of Queensland. The outlook for summer rainfall has taken into account recent changes in Pacific Ocean SSTs, which are bordering on a La Niña classification.

When interpreting seasonal climate outlook information it should be appreciated that seasonal climate outlooks are probabilistic, rather than deterministic, in nature. For example, if an outlook is described as having a 70 per cent probability of exceeding median rainfall, then there will also be a 30 per cent probability of below median rainfall. Furthermore, in cases where there are high probabilities for a specified outcome, it does not mean that a less probable event will not occur.

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