Quarterly Journal of the Royal Meteorological Society Q. J. R. Meteorol. Soc. 141: 350 – 382, January 2015 B DOI:10.1002/qj.2364 Review Article Storminess over the North Atlantic and northwestern Europe – A review F. Feser, a * M. Barcikowska, b O. Krueger, c F. Schenk, d R. Weisse a and L. Xia e a System Analysis and Modelling, Helmholtz-Zentrum Geesthacht, Institute for Coastal Research, Germany b Princeton Environmental Institute, Princeton University, NJ, USA c School of GeoSciences, University of Edinburgh, UK d Department of Mechanics, Royal Institute of Technology, KTH Stockholm, Sweden e Department of Atmospheric Sciences, School of Resource Environment and Earth Science, Yunnan University, Kunming, China *Correspondence to: F. Feser, Institute for Coastal Research, Helmholtz-Zentrum Geesthacht, Zentrum f ¨ ur Material- und K¨ ustenforschung GmbH, Max-Planck-Str. 1, 21502 Geesthacht, Germany. E-mail: frauke.feser@hzg.de This review assesses storm studies over the North Atlantic and northwestern Europe regarding the occurrence of potential long-term trends. Based on a systematic review of available articles, trends are classified according to different geographical regions, datasets, and time periods. Articles that used measurement and proxy data, reanalyses, regional and global climate model data on past and future trends are evaluated for changes in storm climate. The most important result is that trends in storm activity depend critically on the time period analysed. An increase in storm numbers is evident for the reanalyses period for the most recent decades, whereas most long-term studies show merely decadal variability for the last 100 – 150 years. Storm trends derived from reanalyses data and climate model data for the past are mostly limited to the last four to six decades. The majority of these studies find increasing storm activity north of about 55–60 ◦ N over the North Atlantic with a negative tendency southward. This increase from about the 1970s until the mid-1990s is also mirrored by long-term proxies and the North Atlantic Oscillation and constitutes a part of their decadal variability. Studies based on proxy and measurement data or model studies over the North Atlantic for the past which cover more than 100 years show large decadal variations and either no trend or a decrease in storm numbers. Future scenarios until about the year 2100 indicate mostly an increase in winter storm intensity over the North Atlantic and western Europe. However, future trends in total storm numbers are quite heterogeneous and depend on the model generation used. Key Words: storms; storm trends; extratropical cyclones; NAO; North Atlantic; wind Received 17 May 2013; Revised 17 February 2014; Accepted 18 February 2014; Published online in Wiley Online Library 19 May 2014 1. Introduction Storms over the North Atlantic (NA) and northwestern Europe (NWE) have a large impact on population, shipping and offshore industries, forestry and agriculture as well as on buildings and property. The most severe storms in this area occur in wintertime and may lead to high waves and storm surges. At higher atmospheric levels close to the tropopause the polar jet stream develops between cold polar air masses and warm air from the subtropics with strong westerly winds. This wind band is not a straight line, but is often deviated due to the land–sea contrast and takes a meandering path, the Rossby waves form. Within these atmospheric waves low-pressure (over the wave troughs) and high-pressure systems (below the wave crests) evolve, e.g. the Icelandic Low and Azores High. Storms originate in intense low-pressure systems with large temperature and pressure gradients along the Rossby waves. Storms are characterized by strong pressure gradients and high wind speeds, and they may be accompanied by heavy precipitation, hail, thunder and lightning. A storm with strong wind speeds as a result of strong pressure gradients is defined as a wind storm; storminess is used in this article as the state of being stormy. Storminess may be expressed either by direct measures like wind speed or sea-level pressure or by indirect measures, for instance storm-related sea-level variations or storm losses. The path of a storm over time is called a storm track; but this term may also describe track clusters of low-pressure systems in certain geographical regions. One of them is located over the c  2014 Royal Meteorological Society