ECCE Weather Club - Meteorological factors responsible for the Lausanne convectively driven flash-flooding event of 11 June 2018

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Meteorological factors responsible for the Lausanne convectively driven flash-flooding event of 11 June 2018

During the late evening hours of 11.06.2018 a multicell thunderstorm evolving in a maritime tropical airmass advected over the city of Lausanne, Switzerland producing record-breaking rainfall rates over the city, flooding many streets and subway entrances in a very short time and causing nearly 10 million Swiss Francs of damages. An impressive 53.3 mm of rain fell in just 40 minutes, 41 mm of which fell in only 10 minutes, establishing a new Swiss 10-min rainfall rate record. Based on the MeteoSwiss meteorological database, this value represents a return period greater than 80 years. This talk will describe the meteorological synoptic and mesoscale environment that favored this flash-flooding event and also explain some of the atmospheric dynamical processes that were at play. Time permitting, we will also look at some meteorological parameters and tools that forecasters often exploit in the forecast office in order to anticipate and forecast such events as best as possible.