Overview of ESSL's severe convective storms research using the European Severe Weather Database ESWD

Abstract

Severe thunderstorms constitute a major weather hazard in Europe, with an estimated total damage of 5-8 billion euros each year nowadays. Even though there is an upward trend in damage due to increases in vulnerability and possibly also due to climate change impacts, a pan-European database of severe thunderstorm reports in a homogeneous data format did not exist until a few years ago. The development of this European Severe Weather Database (ESWD) provided the final impetus for the establishment of the European Severe Storms Laboratory (ESSL) as a non-profit research organisation in 2006, after having started as an informal network in 2002. Our paper provides an overview of the first research results that have been achieved by ESSL. We start by outlining the reporting practice and quality-control procedure for the database, which has been enhanced by a major software upgrade in the fall of 2008. It becomes apparent that the state of reporting converges to a realistic description of the severe storms climatology, corroborating, for instance, earlier estimates of tornado occurrence in Europe. Nevertheless, a further rise in the number of reported events must be expected, even without the presence of any physical trends. The European tornado and damaging wind intensity distributions as a function of the Fujita scale are quantitatively similar to long-term distributions from the USA, except for a strong underreporting of weak events (F0) that still persists in Europe. In addition, the ESSL has recently proposed a new wind speed scale, the Energy-or "E-scale" which is linked to physical quantities and can be calibrated. Finally, we demonstrate the large potential of ESWD data use for forecast or nowcasting/warning verification purposes.

Tornado Climatology of Finland

“…3), a relatively small number of tornadoes in these countries are strong. The decline with intensity is similar to that seen in Brooks and Doswell (2001) and Dotzek et al (2003). When greater attention is put into collecting reports or there is greater public awareness of tornadoes, as in Ireland (Tyrrell 2003), the relationship is closer to being log-linear.…”

“…We speculate that capping inversions may occur in some of the tornado situations in Finland, which would explain the later maximum of tornado cases compared to the cloud-to-ground flash-rate maximum. Similar diurnal distributions of tornadoes as in Finland occur in France (Dessens and Snow 1989), the United States (Kelly et al 1978), and Germany (Dotzek 2001), for example. The observed diurnal cycle of waterspout cases in Finland with a noon peak is similar to that observed by Dotzek et al (2010) with waterspouts near the German coast at the North Sea and Baltic Sea.…”

“…Similar diurnal distributions of tornadoes as in Finland occur in France (Dessens and Snow 1989), the United States (Kelly et al 1978), and Germany (Dotzek 2001), for example. The observed diurnal cycle of waterspout cases in Finland with a noon peak is similar to that observed by Dotzek et al (2010) with waterspouts near the German coast at the North Sea and Baltic Sea. Distributions with three maxima-two higher peaks near noon and in the late afternoon, and a lower peak in morning-have been observed by Golden (1973) with waterspouts in the Lower Florida Keys and by Sioutas (2011) in Greece (both tornadoes and waterspouts).…”

“…The F4 tornado occurred on 11 July 1934 at Kiuruvesi in central Finland. By comparison, F4 tornadoes have been observed in several other European countries: Estonia (Tooming 2002), Germany (Dotzek 2001), and the Czech Republic (Setvák et al 2003). In France, a few F5 tornadoes have been observed (Paul 2001).…”

“…As in Finland, tornadoes in neighboring Estonia (Tarand 1995) and Sweden (Peterson 1998) occur most frequently during July and August. In central European countries, the peak occurs earlier in the summer: in Germany and in Austria in July (Dotzek 2001;Holzer 2001) and in the Czech Republic and Hungary between May and July (Setvák et al 2003;Szilard 2007). In Mediterranean countries, the peak is in late summer or autumn (e.g., Paul 2001;Gayá et al 2001;Sioutas 2003Sioutas , 2011Giaiotti et al 2007;Gayá 2011).…”