Summer heatwaves in the eastern United States can be predicted up to 50 days in advance, based on the occurrence of a specific pattern of sea surface temperatures in the Pacific Ocean, reports a study published online this week in Nature Geoscience.
Climate change has the potential to exacerbate both the frequency and intensity of summer heatwaves. However, forecasting these events, which could be of significant socioeconomic benefit, has proved challenging.
Karen McKinnon and colleagues identified a cluster of weather stations spanning most of the eastern US where, between 1982 and 2015, hot weather has been observed to occur at the same time. They go on to describe an evolving pattern of Pacific sea surface temperatures that typically precedes heatwaves in these eastern US locations and can be utilized to generate skilful forecasts. Their analysis of the mechanisms shows that the Pacific sea surface temperature pattern leads to anomalies in the bands of propagating high- and low-pressure systems, and to low precipitation over the eastern US, which in turn cause the heatwaves. Finally, the authors demonstrate that their approach could have, in hindsight, predicted the unusually hot summer of 2012, which featured three major heat events that were not well predicted at the time.