Pinto, Joaquim G.Gómara Cardalliaguet, ÍñigoMasato, GiacomoDacre, Helen F.Woollings, TimCaballero, Rodrigo2023-06-192023-06-192014-12-272169-897X10.1002/2014JD022305https://hdl.handle.net/20.500.14352/35094© 2014 American Geophysical Union. We thank the European Centre for Medium-Range Weather Forecasts and the National Centers for Environmental Prediction for the reanalysis data ERA-Interim and NCEP. We also thank the UK Met Office for the weather charts and the Freie Universität Berlin for the storm names. Iñigo Gómara is supported by Spanish national funds (research project MULCLIVAR CGL2012-38923-C02-01). We thank Sven Ulbrich (University of Cologne) and Marc Stringer (University of Reading) for help with data processing. We are grateful to John Methven, Len Shaffrey (both University of Reading), and David Stephenson (University of Exeter) for discussions and Peter Clark (University of Reading) for providing additional synoptic charts. We also thank Olivia Martius and two anonymous reviewers for their helpful and constructive comments. The ERA-Interim Re-analysis data set is available from European Centre for Medium-Range Weather Forecasts (http://apps.ecmwf.int/datasets/). The NCEP reanalysis data set is available from the National Centers for Environmental Prediction (www.ncep.noaa.gov/). The weather charts are available from the UK Met Office (http://www.metoffice.gov.uk), and the storm names from the Freie Universität Berlin (http://www.met.fu-berlin.de/adopt-avortex/). All other data are available from the authors (j.g.pinto@reading.ac.uk)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.engjournal articlehttp://dx.doi.org/10.1002/2014JD022305http://onlinelibrary.wiley.com/open access550.3North-Atlantic oscillationRossby-wave-breakingMoist deformation frontogenesisBaroclinic wavesLife-cycleExplosive cyclogenesisHemisphere winterCritical regionFrontal wavesStorm losses.GeofísicaMeteorología (Física)2507 Geofísica