Serial clustering of extratropical cyclones: a review of where, when and why it occurs

Serial clustering of extratropical cyclones describes the passage of multiple cyclones over a fixed location within a given time period. Such periods often result in high precipitation totals and accumulated wind damage, leading to large societal and financial impacts. Here, we define the terminology to differentiate between several types of cyclone clustering and review multiple approaches used to quantify it. We provide an overview of current research activities including a review of serial cyclone clustering climatologies used to identify where clustering occurs. We review the dynamical mechanisms determining when and why serial cyclone clustering occurs for different timescales of interest. On daily timescales, serial cyclone clustering is often associated with a cyclone family and secondary cyclogenesis mechanisms. At longer timescales, active or inactive seasons are often associated with persistent large-scale flow patterns and their interaction with successive Rossby wave-breaking events. Finally, we discuss the knowledge gaps and current research opportunities.