Monthly Climate Statement for August 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, for much of Queensland the probability of exceeding median summer (November to March) rainfall is currently slightly higher than normal and there is a lower than normal probability of a ‘dry’ summer. However, for some south-eastern parts of the state the probability of exceeding median summer rainfall is lower than normal. Read more (PDF, 254K, last updated 11:46AM, 14 August 2017)*

DSITI provides seasonal outlooks based on SST anomalies in key regions of the tropical and extra-tropical Pacific Ocean which have the most relevance for summer rainfall in Queensland. The current outlook is based on SST anomalies in the extra-tropical Pacific Ocean in March, which tend to persist through to summer. The outlook also considers SST anomalies in the tropical and extra-tropical Pacific Ocean in July, which are strongly related to the ENSO phenomenon.

SST anomalies in the Niño 3.4 region of the Pacific Ocean are a key oceanic indicator of ENSO. The average Niño 3.4 SST anomaly for the three-month May to July period was +0.5°C warmer than normal. However, as at 5 August, the weekly anomaly was only +0.2°C warmer than normal.

Values of the SOI, the key atmospheric indicator of ENSO, have been quite variable over the last three-month period, rising sharply from June to July. In particular, monthly values of the SOI for May, June and July were +0.7, -9.5 and +6.5 respectively.

For Queensland, the relationship between ENSO indices and rainfall for the upcoming summer is strongest in spring. Therefore, DSITI will closely monitor ENSO-related climate indices over the coming months. For each month until November, DSITI will provide updated outlooks for summer rainfall, taking into account any developments in the ENSO-related SST pattern during this period. The summer rainfall outlooks are produced by DSITI’s Seasonal Pacific Ocean Temperature Analysis version 1 (SPOTA-1) system.

It should be noted that seasonal climate outlooks are probabilistic, rather than deterministic, in nature. For example, if an outlook is described as having a 60 per cent probability of exceeding median rainfall, then there will also be a 40 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.

As indicated, DSITI will provide the next updated outlook for summer rainfall in September, to factor in the ENSO-related SST pattern at that time.

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