Observations and simulations of meteotsunamis in south-western Australia

Meteorological tsunamis (meteotsunamis) are water level oscillations that are of
meteorological origin with similar wave forms to tsunami waves. South-western Australia has been identified as a global hot-spot for meteotsunamis with an annual occurrence of ~25 events. Many events, coincide with propagating meteorological events with small changes (~2-3hPa) in atmospheric pressure and were captured opportunistically in coastal tide gauges and moored
instruments (e.g. offshore pressure sensors and ADCP’s). The propagating pressure systems include tropical cyclones, cold fronts, atmospheric gravity waves and thunderstorms. The wave forms generated by each these systems were unique. For example, meteotsunamis generated by a tropical cyclone had two events due to the rotation of the cyclone whilst those generated by the
passage of cold fronts resulted events of longer duration compared to other forcing. In this paper, we present examples meteotsunamis generated by different forcing mechanisms including tropical cyclones, cold fronts and thunderstorms to highlight the range of different processes and their impacts. Severe Tropical Cyclone (TC) Seroja formed on 4 April 2021 off the south coast
of Timor Island Its intensity fluctuated and as it moved to the southwest it interacted with TC Odette to create the Fujiwhara effect. At around 8 pm local time on 11 April, TC Seroja made landfall close to Kalbarri in Western Australia as a Category 3 severe tropical cyclone with strong winds (~170 km/h). Severe damage to the town of Kalbarri was experienced. An extreme water level of 2.5 m was recorded at Geraldton due a meteotsunami and exceeded the extreme high water level reached at this location during the 2004 Indian Ocean tsunami. Similar meteotsunamis events generated by cold fronts and thunderstorms will be described.