Pathways to concurrent North American cold and European wind extremes

We examine near-simultaneous occurrences of cold extremes in North America and wind extremes in Europe, referred to as pan-Atlantic compound extremes. Previous studies have established a robust spatial and temporal relationship between the location of cold extremes and the footprint of wind extremes. Individually, cold and wind extremes are highly impactful, but their coincident occurrence amplifies effects and exposes international actors to correlated losses. This study analyzes the large-scale circulations responsible for pan-Atlantic compound extremes through the lens of weather regimes and Fourier decomposition.

Five distinct dynamical pathways are identified, which non-uniformly govern the occurrence of cold extremes across three regions of North America. Three of these pathways also engender European wind extremes, providing a mechanistic explanation for the observed spatial and temporal relationships of pan-Atlantic extremes. The pathways are as follows:
(i) A persistent Atlantic low producing cold spells in eastern Canada and wind extremes in the British Isles.
(ii) A wave train generating cold spells in the eastern United States, culminating in an Atlantic low and wind extremes in Iberia and the British Isles.
(iii) A wave train producing cold spells in eastern Canada, culminating in Scandinavian blocking.
(iv) A quasi-stationary wave-2 pattern driving cold spells in central Canada and Scandinavian blocking.
(v) An Arctic high generating cold spells in the eastern United States and wind extremes in Iberia.