Storm life cycle modulates extreme hydroclimate impact risk: a Great Lakes Region case study

Extratropical cyclones (ETCs) drive hydroclimate variability in the Great Lakes, yet their impacts vary widely between events. Here, we classify ETCs into two storm types using an unsupervised clustering approach based on storm properties and evolution. The resulting classes differ systematically in life cycle stage at Great Lakes entry. Using bootstrap-estimated risk ratios and risk differences, we show that storms entering later in their life cycle have a higher risk of extreme evaporation during autumn (SON) across all five lakes. In contrast, precipitation responses are weaker, more spatially heterogeneous, and most evident in summer over the upper lakes. Differences in storm genesis location do not fully explain these patterns, indicating that storm evolution at interaction provides a more informative organizing axis. These results demonstrate that storm life cycle stage governs the risk of extreme lake–atmosphere fluxes and offer a transferable framework for storm-centric impact assessment.