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Abstract

Heatwaves have disastrous impacts on human health, ecosystems, and agriculture. Heatwave impacts can be mitigated by early warnings, which were found to effectively reduce the risk from temperature extremes on the sub-seasonal prediction timescale. The quality of heatwave warnings is bound to the predictability of heatwaves, which is mainly investigated in terms of the prediction potential of heatwave intensity. The prediction of heatwave features such as heatwave onset and duration would benefit impact prediction and early warnings. For example, higher mortality risk was previously identified for heatwaves that were more intense, longer, or occurred with earlier timing in the summer. We assess the predictability of heatwave onset, duration, and intensity for the large-scale European heatwaves during 1998-2017. The predictability of heatwave characteristics is evaluated for the lead times of 1—3 weeks in the ECMWF forecast system. The highest predictability in heatwave onset and duration is found over Northern Europe, while Western Europe has the lowest bias in heatwave intensity. Furthermore, we identify the most predictable and least predictable heatwaves over Europe. The most predictable events include the Russian heatwaves of 2010 and 2017, and the 2012 event over Eastern Europe. Some of the least predictable events include the events of 2016 over Russia and of 2017 over Western Europe. The identification of the most and least predictable heatwaves sets the basis for a further investigation of the causes for differences in heatwave predictability over Europe.