Severe Thunderstorm Wind Damage Societal Impacts and Preparedness

Understanding the consequences severe thunderstorms may cause to society helps developing preparedness for such events. Firstly, knowledge on accidents caused by past cases may be used to formulate general guidance for public and authorities. This information may be also used to draft call-to-action statements, which may be included into the warning message. Secondly, knowing what are typical impacts of such an event can help both the general public and authorities to make site specific action plans for the population, private and public properties and for outdoor locations. All these preparedness measures may be used during a severe weather event to prevent casualties. Additionally, if severe weather is forecasted, impact information may be used to prevent property damage or to ensure society's faster recovery by planning ahead the resources needed for both rescue work and repairing damaged infrastructures.

The potential impacts of a specific severe weather event are also influenced by local effects like topography, vegetation, construction standards and local human behaviour. Therefore, the local effects should be considered when defining the typical impacts or guidance template for a certain area. This study describes the bases for defining localized call–to-action statements and impact descriptions in Finland for severe thunderstorms producing wind damage.

The study of two severe thunderstorm events, which caused major wind damage in Finland, showed that most of the emergency calls during these events concerned danger caused by fallen trees. Most often the fallen trees blocked road traffic, and in some cases caused traffic accidents, surrounded vehicles or isolated buildings. Falling trees also typically damaged buildings and electric power lines and the reported casualties were also related to them. Several small boaters were reported in distress on lakes, which seems to be another local consequence for Finland besides falling trees.