Investigation of the weather conditions during the collapse of the Morandi Bridge in Genoa on 14 August 2018

Abstract. On 14 August 2018, Morandi Bridge in Genoa, Italy, collapsed sending vehicles and tons of rubble to the ground about 40 m below and killing 43 people. Preliminary investigations indicated poor design, questionable building practices and insufficient maintenance or a combination of these factors as a possible cause of collapse. However, at the time of collapse, a thunderstorm associated with strong winds, lightning and rain was developed over the city. While it is still not clear whether or not it played a role in this disaster, the present paper documents the weather conditions during the collapse and analyzes in detail a downburst that occurred at the time of the collapse a few kilometers from the bridge. The thunderstorm is analyzed using direct and remote measurements in an attempt to describe the evolution of the cumulonimbus cloud as it approached the coast from the sea. The detected downburst is investigated using a lidar scanner and the anemometric network in the Port of Genoa. The paper shows that the unique lidar measurements enabled a partial reconstruction of the gust front shape and displacement velocity. The Weather Research and Forecasting (WRF) simulations, carried out with three different forcing conditions, forecasted the cumuliform convection at larger scales but did not accurately replicate the downburst signature at the surface that was measured by radar, lidar, and anemometers. This result demonstrates that the localized wind conditions during the collapse time could not be operationally forecasted.