Wildfire synchronicity across European regions is favored by specific weather regimes

Synchronous wildfires (wildfires occurring in multiple locations within a week) pose challenges to coordinated firefighting efforts between European countries. Despite their potentially severe impacts, their occurrence and relationship with predictable atmospheric circulation patterns are poorly understood. We analyze synchronous wildfires across ten European regions over the past two decades and attribute their seasonal occurrences to seven year-round weather regimes. We find that weather regimes modulate the occurrence and spatial extent (the number of regions involved) of synchronous wildfires primarily by driving warm and dry meteorological anomalies, suggesting that these events may become more frequent in a warming world. Specifically, Atlantic Ridge promotes wildfire synchronicity between multiple pairs of European regions in summer, and European Blocking is the most likely regime co-occurring with synchronous wildfires spanning large spatial domains (or involving more than five regions) in spring and fall. Our findings could support early warning systems for synchronous wildfire emergencies in Europe because these weather regimes are predictable on subseasonal timescales.