March 8, 1977 Tsunami: Cassino Beach, Rio Grande do Sul, Brazil

There were no related data, but according to the news, three high waves suddenly hit the beach, covering cars, dragging bathers’ belongings, and also causing a casualty. Yet according to the news, eyewitnesses estimated the episode lasted around 10 min, after the sky had turned dark and the wind changed direction erratically. In fact, there are doubts if 10 min was the length of time of the whole event or the period of each wave. Sea-level pressure and wind fields extracted from the reanalysis for March 7 and 8, 1977 show a deep low-pressure system with strong associated winds located south of the region and moving to the southeast. This situation certainly generated instability conditions in the region. Melo Filho et al. (2005) speculated that the forcing factor could be short atmospheric gravitational waves or an atmospheric pressure jump, which generated a squall line. Unfortunately, there are no data to confirm these hypotheses. With existing information, it can be classified as a “good-weather open-coast event”. (reference #13945)