A refined analysis of thunderstorm outflow characteristics relevant to the wind loading of structures

The study of thunderstorm outflows and their loading and response of structures is a key topic in modern wind engineering. This paper provides a new contribution to this research by analyzing a wide dataset of 277 wind velocity records characterized by strong transient properties and labeled by thunderstorm outflow. These records have been detected for up to 6 years by 14 anemometers belonging to an extensive in-site monitoring network distributed in the Northern Mediterranean ports. Analyses are carried out in order to extract the parameters of major interest for evaluating the wind loading effects of structures and furnishing a comprehensive statistical characterization of the huge amount of data recorded. Results lead to a novel classification of thunderstorm outflows with reference to the time scale of the gust front passage and their intensity; a refined interpretation of the differences involved by the turbulence intensity, the integral length scale and the gust factor of mesoscale downbursts and synoptic low-pressure systems; a confirmation of the substantial independence of these quantities with respect to the ratio between the height above ground of the sensor and the roughness length of the terrain, together with their correlation with the wind velocity; a new parameterization of the harmonic content of the turbulent fluctuations.