The harbour at Stonehaven, on Scotland’s east coast, is normally tranquil but, at 7.30pm on 1 July 2015, the sea did something strange.
“The water suddenly started to rush out for about five minutes, dropping by about 1.25 metres, then after a couple of minutes returned with some force,” reported the harbourmaster. This tsunami-like event damaged boats and resulted in a serious head injury to one crewman. Analysis suggests that this mini-tsunami was brought on by the thundery weather.
At the Met Office, Andrew Sibley and his colleagues have analysed weather observations and radar images. Their results show a sharp spike in air pressure racing along in front of the thunderstorms. It seems the upwards convection associated with the storm, was balanced by powerful downdrafts in front of the storm system. This high pressure spike was enough to push the level of the North Sea down as much as 5cm and, with resonance in relatively shallow water, set up a tsunami-like wave.
Tidal gauges along the east coast of Scotland confirm the existence of this wave, which probably wasn’t a freak event. “They seem to occur as frequently as every three to ten years around the UK, and are relatively common globally too,” says Sibley, whose findings are published in the journal Weather. Indeed a similar event was seen in the Channel in June 2011. Greater understanding of these meteotsunamis should enable meteorologists to forecast them in future, giving people more time to get out of harm’s way.
