The Washington PostDemocracy Dies in Darkness

Last night’s thunderstorms caused a meteotsunami along the Northeast coast

Storm clouds gather over New York City as seen from the Hudson River on Tuesday. A line of strong storms pushed across New York City and badly disrupted the evening commute, stranding thousands of train riders. (Denis Paquin/AP)

On Tuesday night, just after a line of severe thunderstorms rolled over the East Coast and out into the Atlantic, tidal gauges recorded something interesting from Delaware to southern New England. The pressure rose and fell sharply, and then water levels climbed higher than they should have given the tide at the time.

It was a meteotsunami, which is exactly what it sounds like — a tsunami triggered by the weather.

According to NOAA, meteotsunamis are possible in many lakes, seas and oceans around the world when conditions are right. Some have even been observed to reach six feet or higher. That being said, they still tend to be smaller than true tsunamis, which are usually triggered by earthquakes.

Meteotsunamis happen when air pressure jumps rapidly. We see them a lot when fast-moving thunderstorms blow out over the ocean, like derechos or the line of storms that swept across the Northeast on Tuesday night. The storm generates a wave, NOAA says, which moves toward the shore and gets amplified when it hits shallow water.

We’ve seen several meteotsunamis off the East Coast in the past few years, including during the 2012 derecho and a similar storm in 2013. Tuesday night, abnormal tides were recorded through the evening. On the gauges, it looked like large waves rolling onto the shore.

It’s still difficult to predict when a meteotsunami will happen, but it’s not impossible, especially since we now have a better idea of what causes them. Eventually we will see meteotsunami warnings along the coast during severe weather situations.