Abstract The study investigates the occurrence of an unusual tidal event recorded at Portsalon Golf Club on 21st February 2022 at 08:50 UTC. The event followed the passage of Storm Franklin and was described by the videographer as a “rather unusual storm surge”, prompting the evaluation of multiple event types to identify the most likely cause: Storm Surge, High-Tide Seiching, Freak Wave, Meteotsunami or Tsunami. Through the use of 5-min tidal observations, 1-min meteorological station data and ERA5 reanalysis products, sea-level and atmospheric variability and synoptic conditions prior to and during the videoed event were examined. Results highlight evidence of elevated non-tidal variability coinciding with strong winds and high wave height (~ 12 m) near the mouth of Lough Swilly following the passage of Storm Franklin. Oscillations recorded at Letterkenny tidal gauge on the approach to high tide suggest the possibility of seiching within Louch Swilly. Background conditions often associated with Meteotsunamis, such as the presence of a strong jet stream and area of high relative humidity, were present, however no clear or particularly rapid atmospheric pressure disruption was found that temporally aligned with the observed wave. Neither the prevailing wind or wave direction suggested a freak wave was a contributing factor, and no spatially or temporally relevant seismic activity was recorded. The most likely explanation of the videoed event is the combination of a weakening storm surge amplified by high-tide seiching in Lough Swilly. Limitations in analysis highlight the need for higher-frequency coastal monitoring to aid the classification of such hazards.
Swan et al. (Mon,) studied this question.
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