The Department of Environment and Science (DES) monitors sea-surface temperature (SST) anomalies in key regions of the Pacific Ocean over autumn, winter and spring and provides objective outlooks for Queensland summer (November to March) rainfall on this basis. The Climate Variability Unit of DES will provide an initial outlook for next summer in the next (April) Monthly Climate Statement. Read more (PDF)*
Rainfall in Queensland over spring and summer is influenced by the El Niño-Southern Oscillation (ENSO) — a coupled atmospheric and oceanic phenomenon which is persistent at seasonal timescales. However, at this time of year (known as the ‘autumn predictability gap’), ENSO-related SST anomalies tend to break down and, for this reason, do not provide a reliable indicator of upcoming seasonal rainfall.
The La Niña pattern, which developed in spring last year, has persisted through summer as anticipated. In Queensland, La Niña conditions tend to be, but are not always, associated with above-median (> decile 5) summer rainfall. This summer rainfall has been above-median in some north-western and south-eastern parts of the State, but below-median in many other areas.
La Niña conditions are characterised by cooler than average SSTs in the Niño 3.4 region of the Pacific Ocean, coupled with sustained positive values of the Southern Oscillation Index (SOI). Over the last three months (December to February), the average SST anomaly in the Niño 3.4 region (-0.8°C) remained cooler than average. However, the three-month average value of the SOI (-0.5) has returned to a neutral value. Due to this change in the SOI and other atmospheric indicators, as well as some evidence of recent Pacific Ocean warming, the Bureau of Meteorology now (as at 13 March 2018) consider that ENSO conditions have returned to a neutral state.
DES will provide an initial outlook for summer rainfall in April, which will be updated each month from June to November. The initial outlook is based on SSTs that are not related to ENSO at this time of year. The updates from June to November will take into account the evolving ENSO-related SST pattern at that time.
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