What is a meteotsunami?

First of all, what is a meteotsunami? So, you will all have probably heard of a tsunami especially after the 2004 Boxing day Pacific Ocean event. So, tsunami waves are basically shallow water waves of 2 mins to 2hrs which are caused by underwater seismic activity or landslides. A meteotsunami is basically a tsunami wave, but the trigger event is not seismic it’s atmospherically generated by weather events such as cyclones, squalls, thunderstorms and gravity waves.

A meteotsunami stirs to life when a thunderstorm, or some other major weather event roars across the ocean. The storm causes a big but quick change in air pressure and winds, this can create a wave on the water. The wave is small at first – around 3cm high. But as it moves towards the coast it gains amplification by what we call the Proudman resonance. This is basically when the atmospheric system moves at the same speed as the wave underneath it and subsequently feeds the wave with energy forcing it to grow. As the wave reaches shallower waters this causes it to pile up and the wave begins to shoal. As it enters a bay or harbour it will then use the local coastline characteristics to resonate. Eventually, it can reach several metres in height -- big enough to cause damage.

Here in the UK, meteotsunamis are most common along the Southwest coast and up through the channel into the North Sea due to the prevailing weather conditions. Most of them aren’t that big, so no one really notices. The largest ever identified and recorded meteotsunami here in the UK was a 6m wave that hit the English Channel in 1858, however, on average the wave height of a UK meteotsunami is around. 2.6m.

Unfortunately, due to a lack of knowledge and a suitable enough high frequency tide gauge network that records less than the current 15 minutes many events appear to either go undocumented or be mis-labelled as events of ‘unknown origin’ or storm surges.