Large‐scale dynamics associated with clustering of extratropical cyclones affecting Western Europe

Abstract

Some recent winters in Western Europe have been characterized by the occurrence of multiple extratropical cyclones following a similar path. The occurrence of such cyclone clusters leads to large socio-economic impacts due to damaging winds, storm surges, and floods. Recent studies have statistically characterized the clustering of extratropical cyclones over the North Atlantic and Europe and hypothesized potential physical mechanisms responsible for their formation. Here we analyze 4 months characterized by multiple cyclones over Western Europe (February 1990, January 1993, December 1999, and January 2007. The evolution of the eddy driven jet stream, Rossby wave-breaking, and upstream/downstream cyclone development are investigated to infer the role of the large-scale flow and to determine if clustered cyclones are related to each other. Results suggest that optimal conditions for the occurrence of cyclone clusters are provided by a recurrent extension of an intensified eddy driven jet toward Western Europe lasting at least 1 week. Multiple Rossby wave-breaking occurrences on both the poleward and equatorward flanks of the jet contribute to the development of these anomalous large-scale conditions. The analysis of the daily weather charts reveals that upstream cyclone development (secondary cyclogenesis, where new cyclones are generated on the trailing fronts of mature cyclones) is strongly related to cyclone clustering, with multiple cyclones developing on a single jet streak. The present analysis permits a deeper understanding of the physical reasons leading to the occurrence of cyclone families over the North Atlantic, enabling a better estimation of the associated cumulative risk over Europe.

Robustness of serial clustering of extratropical cyclones to the choice of tracking method

“…The maintenance of these large-scale conditions is supported by two-sided Rossby wave breaking over the North Atlantic (Hanley and Caballero, 2012;Go´mara et al, 2014;Messori and Caballero, 2015). Pinto et al (2014) demonstrated for four selected stormy periods 1990, 1993, 1999 and 2007 that secondary cyclogenesis (new storms develop on the trailing fronts of previous storms, cf . Parker, 1998) further contributes to the occurrence of cyclone clusters arriving into Western Europe in rapid succession.…”

“…Such stormy winters are characterised by the frequent occurrence of cyclone families (Bjerknes and Solberg, 1922). Pinto et al (2014) recently provided evidence that the occurrence of cyclone clusters is governed by a persistent, zonally orientated and extended eddy-driven polar jet stream over the eastern North Atlantic and Western Europe, which drives the North Atlantic cyclones towards the British Isles and sometimes further into Central Europe. The maintenance of these large-scale conditions is supported by two-sided Rossby wave breaking over the North Atlantic (Hanley and Caballero, 2012;Go´mara et al, 2014;Messori and Caballero, 2015).…”

Reanalysis comparisons of upper tropospheric–lower stratospheric jets and multiple tropopauses

“…Variations in the UTLS jets influence influence surface weather patterns (e.g., see reviews by Lucas et al, 2014;Harnik et al, 2016) such as rainfall changes (e.g., Price et al, 1998;Raible et al, 2004;Karnauskas and Ummenhofer, 2014;Huang et al, 2015;Xie et al, 2015;Delworth and Zeng, 2014;Bai et al, 2016), destructive wind storms (e.g., Pinto et al, 2009Pinto et al, , 2014Gómara et al, 2014;Messori and Caballero, 2015), and extreme temperature events (e.g., Francis and Vavrus, 2012;Harnik et al, 2016). Moreover, transport processes that alter the extent and consequences of extratropical stratosphere-troposphere exchange (STE) are closely linked to the tropopause and jets, which are themselves sensitive to climate change and ozone depletion (e.g., Seidel and Randel, 2006;Lorenz and DeWeaver, 2007;Polvani et al, 2011;WMO, 2011;Hudson, 2012;Grise et al, 2013;Waugh et al, 2015).…”

Epistemic uncertainties and natural hazard risk assessment. 1. A review of different natural hazard areas

“…This research raised much awareness about clustering in the natural catastrophe insurance industry that has led to major developments in windstorm catastrophe models (Khare et al 2014). The findings are also stimulating new research into mechanisms for clustering of extreme storms (e.g., Rossby wave breaking; Pinto et al, 2014). 15…”