Using analogue methods to identify trends in circulation patterns of midlatitude heatwaves

Circulation analogues are useful tools for extreme event assessment. They can be used to assess changes in the dynamical conditions associated with a specific extreme event. Here, we use circulation analogues to investigate a set of six midlatitude heat extremes, spanning all midlatitude continents. We objectively assess some of the decisions required when selecting circulation analogues. We show the choice of analogue domain, climatic variable, and similarity metric influence how well the analogues capture the magnitude of the meteorological hazard of the event itself. We show that, due to the complex nature of the climate system, each event requires individual assessment to determine how to select analogues that best represent the hazard. For the six case studies, we present an assessment of analogues using the workflow identified. Some events show significant dynamical changes between 1950-1980 and 1994-2024, which could act to amplify extreme heat. We show that, for midlatitude heatwaves, circulation analogues can provide useful information about temporal changes in circulation patterns of similar events. We provide a workflow for the use of circulation analogues within operational detection and attribution studies, with a publicly available online Climate Explorer tool. • Circulation analogues can be used to assess if a specific weather pattern is changing through time. • Selecting analogues requires several decisions, such as which circulation variables to use, how many analogues to select, and which region to assess. • Even when considering six midlatitude heat extremes we show different events require different methodology choices. • We assess some of the choices to develop a methodology which selects analogues that are best linked to the meteorological hazard, ensuring conclusions are relevant to society. • We present a Climate Explorer tool enabling the use of the workflow present herein: https://climexp.knmi.nl/analoguesform.cgi .