The role of large-scale atmospheric flow and Rossby wave breaking in the evolution of extreme windstorms over Europe

Authors

  • John Hanley,

    Corresponding author
    1. Department of Meteorology, Stockholm University, Stockholm, Sweden
    2. Bert Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
    • Corresponding author: J. Hanley, Department of Meteorology, Stockholm University, Stockholm SE-106 91, Sweden. (john@misu.su.se)

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  • Rodrigo Caballero

    1. Department of Meteorology, Stockholm University, Stockholm, Sweden
    2. Bert Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
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Abstract

[1] We investigate the relationship between large-scale atmospheric flow and the evolution of the most extreme windstorms affecting Western Continental Europe. The 25 most destructive Western Continental European wind storms are selected from a 43-year climatology. 22 of these storms are grouped as having a similar trajectory and evolution. We show that these storms typically occur during particularly strong and persistent positive NAO anomalies which peak approximately 2 days before the storms' peak intensity; the NAO pattern then shifts eastward to a position over the European continent when the storms strike Europe. A temporal composite of potential temperature on the 2-PVU surface suggests that this NAO shift is the result of simultaneous cyclonic and anticyclonic wave breaking penetrating further to the east than during a typical high-NAO event. This creates an extremely intense, zonally-orientated jet over the North Atlantic whose baroclinicity favours explosive intensification of storms while steering them into Western Continental Europe.

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