Extratropical Cyclones leading to Extreme Weather Events over Central and Eastern North America

Cool-season extreme weather events (EWEs) occurring over central and eastern North America are typically associated with strong extratropical cyclones (ECs) that are governed by varying combinations of baroclinic, diabatic, and barotropic processes. This presentation investigates the climatology and evolution of ECs leading to EWEs over central and eastern North America, and provides a foundation on which to compare ECs leading to EWEs with ordinary ECs forming over and traversing the same regions. A climatology of ECs leading to EWEs over central and eastern North America during October–March 1979–2016 reveals that these ECs typically form 1) in the lee of the Rocky Mountains, 2) over the south central U.S., and 3) along the east coast of North America at latitudes equatorward of the typical genesis locations of ordinary ECs. Metrics representing baroclinic, diabatic, and barotropic processes are calculated as regional averages of their applicable Lorenz (1955) energy generation and conversion terms during the evolution of ECs leading to EWEs and the evolution of ordinary ECs over central and eastern North America during October–March 1979–2016. These metrics reveal that ECs leading to EWEs are associated with contributions from baroclinic, diabatic, and barotropic processes that are 1) similar to those associated with ordinary ECs at the time of formation and 2) considerably larger than those associated with ordinary ECs at the time of maximum intensity.