Numerical investigation of the December 2019 seiche event in the Adriatic Sea

In this work, we present the preliminary results of a study of a series of seiches, which occurred during the month of December 2019 in the Adriatic. A  peculiar aspect of this event is that it was not preceded by any significant storm surge, which usually triggers the normal modes of the Adriatic Sea. With the aim of investigating the dynamics of the event, we used the sea levels observed at some coastal locations and a hydrodynamic finite element model. The model, already used in numerous studies of the area, was applied in a diagnostic way, by varying the forcing to demonstrate its importance for the event. We hypothesise that the first normal mode was excited by a variable wind forcing having a period close to the one of the main normal mode (about 21 hours). Consequently, the excitation of the normal mode was nearly resonant.