Data evaluation for North Rhine-Westphalia 180 continuous and heavy rain storms in NRW in 2021
Essen · Extreme rainfall events have repeatedly caused major damage in recent years, most recently on a catastrophic scale in July. An evaluation for North Rhine-Westphalia shows that there were especially many heavy and continuous rain storms in 2021.
This year, meteorologists in North Rhine-Westphalia have recorded more heavy and continuous rain storms than at any time in at least 20 years. This is the finding of a preliminary report of the German Weather Service (DWD) referencing data since 2001. According to the data, in the year that is coming to an end, around 180 "precipitation events" were counted in NRW on the basis of radar data, which were classified by the DWD as severe weather or even extreme severe weather. The catastrophic continuous rainfall lasting several days in July was recorded by the experts as a single, continuous event. In addition, there were two distinct smaller storms in the north of the state in that period.
The previous annual record of around 170 such events was recorded in 2014. In 2006 and 2018, too, there were comparatively frequent rainstorms of severe intensity, with around 160 events each. The lowest number was recorded in 2001, with around 38 events. The numbers vary greatly from year to year. In 2002, for example, 143 events were recorded. One year later, there were significantly fewer: 78.
The experts record the events in eleven stages according to their duration: From one hour to 72 hours. "The most and strongest heavy rainfall events are to be expected in the climatological summer in the months of June, July and August - followed by May," explained Thomas Kesseler-Lauterkorn from the DWD's Essen Regional Climate Office. In the months of October to March, on the other hand, precipitation storms are registered comparatively rarely.
At the end of October, the Federal Agency for Cartography and Geodesy (BKG) published a high-resolution interactive web map with hazard warnings for heavy rain in North Rhine-Westphalia. The map shows exactly where water can accumulate within an hour in the event of an extreme rainfall of 90 liters per square meter and how high the water level is likely to be.
At a specialist symposium at the beginning of December, NRW Environment Minister Ursula Heinen-Esser (CDU) called on local authorities to develop municipal heavy rainfall hazard maps and action plans based on them. "Such maps and their consistent application can help contain the consequences of destructive forces of nature," she said. According to the Environment Ministry, more than 50 municipalities have already developed municipal or regional heavy rain hazard maps, including Dortmund, Cologne and Wuppertal.
In mid-July, depression "Bernd" caused devastating floods in North Rhine-Westphalia and Rhineland-Palatinate. The rainfall was extreme, with large areas receiving over 100 liters per square meter in 24 hours. The DWD station in Wipperfürth-Gardeweg recorded 162.4 liters per square meter in 24 hours on July 14. The highest amount of precipitation in NRW was measured at a station of the State Environment Agency in Hagen with 241.3 liters within only 22 hours. By way of comparison, an average of 240 liters fell in NRW in the three months of June, July and August combined from 1961 to 1990.
Orig. text: dpa
Translation: ck
