What is a meteotsunami?

When intense storms move over open water, they can generate a wall of water known as a meteotsunami, an uncommon event that can cause damage along the coast of bodies of water.

These events can be difficult to predict and can range from small, almost undetectable waves of water to larger waves that can inundate coastal areas.

"Meteotsunamis have characteristics similar to earthquake-generated tsunamis, but they are caused by air pressure disturbances often associated with fast-moving weather systems," the National Weather Service (NWS) said.

A fast-moving line of storms, such as a squall line or derecho, can be strong enough to trigger a meteotsunami in addition to other dangers such as powerful winds and frequent lightning.

"The storm generates a wave that moves toward the shore, and is amplified by a shallow continental shelf and inlet, bay or other coastal feature," AccuWeather Senior Meteorologist Alex Sosnowski said.

Shelf cloud
Shelf cloud

(Photo/NOAA/Michelle Mcgahey)

Meteotsunamis tend to be regional in nature, unlike tsunamis set off by earthquakes which can be far-reaching and impact a significant stretch of coastline.

"In the United States, conditions for destructive meteotsunamis are most favorable along the East coast, Gulf of Mexico, and in the Great Lakes, where they may pose a greater threat than earthquake-generated tsunamis," the NWS said.

The phenomenon has also been observed around the world, including in the Mediterranean Sea, the Adriatic Sea and off the coast of Australia.

Some meteotsunamis are relatively small and may occur without being noticed.

This was the case on May 15, 2018, when a line of severe storms blasted through the mid-Atlantic and triggered a meteotsunami along part of the region's coast.

Water gauges in the area measured a change in water level of several inches, too small for many people to distinguish apart from normal waves.

However, others can be significant and bring life-threatening conditions.

"The strongest meteotsunami on record struck Vela Luka, Croatia, in June 1978. The event featured 19.5-foot wave heights, lasted several hours, and caused significant damage to the port and boats," the NWS said.

One of the largest meteotsunamis on record in the U.S. hit the Boothbay Harbor in Maine in 2008.

Waves up to 12 feet were recorded with the harbor flooding and emptying out three times over 15 minutes. These waves damaged boats and infrastructure across the area.

An even larger meteotsunami was reported on Lake Michigan in 1929 when a 20-foot wave crashed into Grand Haven, Michigan. Ten people died after being swept out into the lake by the wave.

While meteotsunamis can pose a danger to coastal communities, predicting when they will occur and how large they will be remains a challenge.

Additionally, they can be hard to distinguish from other weather-generated waves, such as storm surge or a seiche, or a wave oscillating in a semi- or fully-enclosed body of water.

"The United States is still in the early stages of developing a meteotsunami forecast and warning system," the NWS said.

"Led by NOAA, these efforts include developing a process that outlines when, where, and how meteotsunami warnings should be issued based on high resolution air pressure measurements combined with meteotsunami forecast models," the NWS added.