At 18 August 2011 a severe thunderstorm system developed over Belgium. It initiated over France and then passed over Belgium, the Netherlands and Germany. The studied thunderstorm grew fast and was long-lived. It was extremely severe; particularly the downdraft was extremely strong. The most intense part of the windstorm hit the Pukkelpop festival organized close to the city of Hasselt. There were 60 thousand people at the festival, staying mainly at the camping site. The strong wind flattened tents, uprooted trees, brought down festival light towers and TV screens, and caused a stage to collapse. Five people were killed and 140 people injured in the storm, ten of them seriously.
The aim of this case study is to describe the synoptic situation in which the windstorm was initiated and developed, and to describe its characteristics by means of satellite, radar and lightning data and numerical simulation.
Fig. 1.1. Camping site on the next day
Fig. 1.2. The storm damaged trees
Fig. 1.3. Collapsed stages
Fig. 1.4. Location of the Pukkelpop festival, Kiewit (indicated by letter "A") north from the city of Hasselt.