Tornadoes in Germany

A climatology of tornadoes in Germany using the TorDACH database up to the year 2000 is presented. The total number of tornadoes is 517 and the number of reports has increased substantially after 1870. Tornado activity is at maximum in July, and at minimum from November to February. The daily distribution peaks in the afternoon and early evening with a weak secondary morning maximum due to waterspout outbreaks. In general, both daily and seasonal trends follow the variation of thunderstorm activity. The highest F-scale rating so far is F4 and in the range from F1 to F4 a nearly lin-log distribution of tornado intensity is found. The low number of reported F0 tornadoes indicates that perhaps only every third tornado in Germany is reported. Also, the geographical distribution shows that many cases from east Germany are missing. However, three different regions of typical tornado activity can be inferred: the northern coastal region, the hilly terrain of mid and southern Germany, and a zone influenced by Mediterranean air in summer and an orogenic low-level wind shear in the south-west. For the latter, an example of a tornado alley is given. From a conservative estimate of tornadic activity in Germany, a number of four to seven tornadoes per year and a recurrence density of about 0.1 to 0.2 a(-1) 10(-4) km(-2) is deduced, in accordance with earlier work. However, both extrapolation based on statistical arguments and the more detailed records of recent years suggest values a factor of three to four higher. (C) 2001 Elsevier Science B.V. All rights reserved.