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Analysis of the Adriatic storm surge and meteotsunami of 29 October 2018

During night hours of 29-30 October, a north- eastward propagating cyclone which originated in the western Mediterranean crossed the Adriatic. An associated pressure drop and strong sirocco winds resulted in flooding of the middle and northern Adriatic: 4th highest Aqua Alta of the measurement period was recorded in Venice (Venice Municipality, 30/10/2018), 1st highest sea level of the measurement period was recorded in Bakar (GFZ, 2018), many harbours and boats suffered material damage and extreme waves were observed and recorded throughout the Adriatic. Although there were no public meteotsunami reports, available tide gauge data reveals that a weak meteotsunami occurred in Vela Luka between 20:00-24:00 UTC of 29 October. Maximum meteotsunami wave at tide gauge location had a height of 94.0 cm. Associated to this wave was maximum sea level of 63.4 recorded at 20:32 UTC, which was also time of a high tide. Mean period of Vela Luka waves was ~12 min. Increased high frequency sea level activity, but of lower intensity, was recorded at other middle Adriatic tide gauge stations as well, including Stari Grad (Hvar Island), Sobra (Mljet Island), and Split. Air pressure measurements reveal that numerous potentially tsunamigenic high-frequency atmospheric disturbances propagated over the middle Adriatic during the event. These disturbances were especially strong over Vela Luka area, where several consecutive oscillations of up to 5-min duration, and crest-to-through heights of ~1 hPa were measured. Synoptic setting leading to the event is analysed in detail using ERA5 reanalysis dataset and available air pressure and wind measurements. It is shown that during October the Adriatic Sea was on the front side of a 500 mb trough, and that a low pressure trough on 850 mb was located over the western Mediterranean. This pattern was supporting warm air advection from the SW, and preconditioning generation of the Mediterranean cyclone. Available tide gauge records are analysed to estimate contribution of different processes to the flooding, including tides, storm surges, and meteotsunamis.

Storm surge ; meteotsunami ; Adriatic Sea

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