Multiple large-scale dynamical pathways for pan--Atlantic compound cold
and windy extremes
Abstract
Winter cold spells over North America have been correlated with European
wind extremes, but the physical mechanisms behind such “pan-Atlantic”
compound extremes have not been clarified yet. In this study, we propose
that pan–Atlantic cold and windy extremes occur following two possible
dynamical pathways. The first one involves the propagation of a Rossby
wave train from the Pacific Ocean, associated with windstorms over
north-western Europe in the 5-10 days after the cold spell peak. The
second is associated with a high-latitude anticyclone over the North
Atlantic and an equatorward-shifted jet, leading to windstorms over
south-western Europe already in the days preceding the cold spell peak.
European windstorms are thus consistently tied to North American cold
spells according to the different flow configuration. The analysis
underscores that seemingly similar surface extremes may be driven by
different processes, and that overlooking these subtleties and
conflating them together could lead to misleading conclusions.