Elsevier

Atmospheric Research

Volumes 67–68, July–September 2003, Pages 153-161
Atmospheric Research

An updated estimate of tornado occurrence in Europe

https://doi.org/10.1016/S0169-8095(03)00049-8Get rights and content

Abstract

Results from a survey on average tornadic activity in Europe conducted among the participants of the European Conference on Severe Storms (ECSS) 2002 are presented. Compared to Alfred Wegener's estimate of “at least 100 tornadoes per year in Europe” the present survey shows a total of 329±12 tornadoes over land and water per year based on observations, and more than twice as many cases (697±36) for an estimate of the expected true climatological number, accounting for present underreporting in many European countries. Traditionally, European tornado numbers include waterspouts. For comparison to the current number of 1170 observed tornadoes over land per year in the USA, the European numbers are 169±9 per year based on observations, and 304±25 based on estimates. As European severe weather research is rapidly developing, one can expect less underreporting in the future, leading to an augmented database for upcoming surveys like the present one.

Introduction

After the European Conference on Tornadoes and Severe Storms (ETSS) held in Toulouse in February 2000 (Snow and Dessens, 2001), one question remained unanswered: how many tornadoes are there in Europe as a whole on average each year?

During the ETSS follow-up, the European Conference on Severe Storms (ECSS 2002) in Prague, the author distributed a survey among the participants coming from 28 different countries, to update an estimate of this important number which has stood for over eight decades: Wegener (1917, p. 84) gave this estimate of “at least 100 tornadoes per year in Europe” based on his thorough analysis of historical and contemporary tornado reports.

In his book, he stated that “Tornadoes and waterspouts are identical phenomena, only that the former term is used over land, while the latter is used over the sea. Should it happen that small underlying differences between the two are discovered, something that has certainly not happened until now, these will presumably be attributable to the differences in surface friction” (Wegener, 1917, p. 3, cf. Appendix A).

Further, he defined tornadoes and waterspouts alike as “large vortices with vertical axis extending from the base of a cumulonimbus cloud to the surface, visible completely or in part through condensation or, in the lower part through dust, in the form of a pendant cone, funnel, hose or column. In a track typically on the order of hundreds of meters wide, with intense convergence towards the region of strongly reduced air pressure around the vortex axis, they in general cause damage of a kind not observed in even the strongest larger scale storms” (Wegener, 1917, p. 5, cf. Appendix A).

These definitions were well ahead of their time. The often cited, but not very helpful, definition of the Glossary of Meteorology's first edition (Huschke, 1959) has been a subject of criticism for many years. Only recently, the second edition of the Glossary (Glickman, 2000) provided a similar definition to Wegener's given 83 years before. In this paper, the notion is adopted that tornadoes and waterspouts represent the same basic physical phenomenon described by Wegener's and Glickman's definitions.

To address the question on how many tornadoes there are in Europe, Section 2 reviews the data from the ECSS 2002 survey, while Section 3 briefly discusses the data and current European severe weather research activities. Section 4 presents the conclusions.

Section snippets

Survey data

A total of 26 survey forms were returned, including two slightly differing ones from Germany. All names of participants were given on the forms. Usually one, but up to five people contributed to each form. These participants were well acquainted with their national tornado climatology or even keepers of the national tornado record.

The survey data are outlined in Table 1 for tornadoes over land surfaces, and in Table 2 for tornadoes over water surfaces, i.e. waterspouts. Both tables give two

Discussion

When interpreting the numbers from this first survey on tornadoes in Europe since the work of Wegener (1917), some care must be taken. For example, some countries have just initiated tornado research and base their observations and estimates on rather short or intermittent time series. Other countries have homogeneous records going back many centuries. The level of uncertainty in the survey results is therefore much larger than indicated by the quite tight “error bars” in Table 3. Yet as severe

Conclusions

The climatological survey on tornadoes in Europe during the European Conference on Severe Storms in Prague showed the following:

  • Based on data from 25 countries, about 170 tornadoes over land, and 160 waterspouts are currently observed in Europe each year on average.

  • The number given by Wegener (1917) was reasonable, given the data available at the time.

  • Estimated numbers from 28 countries indicate roughly 300 cases per year for tornadoes and 390 per year for waterspouts.

  • Total numbers for all

Acknowledgements

The author is grateful to all participants of the ECSS 2002 in Prague who contributed to this study. George Craig, Thorsten Fehr, Fulvio Stel, and Jürgen Grieser carefully read draft versions of the paper and contributed valuable suggestions.

Information on mentioned projects and groups is available for the ESSL: www.essl.org, ESWD: www.eswd.osmer.fvg.it, ESTOFEX: www.estofex.org, Skywarn Europe: www.skywarn.eu, and TorDACH: www.tordach.org.

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