Investigation of the passage of a derecho in Belgium

From the 7th July, 2010 until 14th July, 2010, a heat wave dominated the weather in Belgium. Three major storm situations occurred during this period and all three caused severe damage. In this paper, we discuss the last storm case of 14th July. That day, a quasi-linear convective system (QLCS) crossed parts of France, Belgium and the Netherlands and caused very important wind damages and at least 2 people were killed. Most of the damage was caused by straight-line wind but at least one tornado was observed over the north of the Netherlands. This complex was induced in a very favorable synoptic configuration for severe weather and also the timing of the storm was favorable. In the frame of the Supercell project at the RMI, a damage survey was made of one of the most affected regions, which yielded useful information about the origin of the losses. l examination of the radar imagery revealed some connections between internal mesovortices and tracks of enhanced damage. As far as known, this paper is the first description of a derecho in Belgium. It is also the first time a connection is shown between some mesovortices and several damage tracks over the country. During the evolution of the QLCS, several examples of successive vortices were found in front of the system. Several of the vortices were accompanied by a tornado or a funnel cloud and the damage was typically concentrated along elongated tracks.