Study promises to predict meteotsunamis

On the afternoon of April 13, 2018, a large wave of water swept over Lake Michigan and flooded the shores of the scenic seaside town of Ludington, Michigan, damaging homes and boat docks and flooding the intake pipes. Using photos from a local citizen and other data, NOAA scientists reconstructed the event in models and determined that it was the first meteotsunami ever documented in the Great Lakes caused by a wave. atmospheric inertia-gravity.

An atmospheric inertia-gravity wave is an air wave that can travel 6 to 60 miles in length, created when a stable air mass is moved by an air mass with significantly different pressure. This sets in motion a wave of air with rising and falling pressure that can influence the water below, as it synchronizes with the movement of water on the surface of the lake like two singers harmonizing.

“This meteotsunami was definitely awesome,” said Debbie Maglothin of Ludington who took pictures of the event. “The water between the breakwaters didn’t go down like the water outside them, so it created waterfalls that cascaded over the breakwaters. If this event had happened during the summer, it could have washed people directly from the breakwaters.

Meteotsunamis generated by this type of atmospheric condition are common around the world, but in the Great Lakes, the few well-documented meteotsunamis have been swept away by sudden severe thunderstorms where winds and changes in atmospheric pressure played an important role.

Combination of aquatic and meteorological models

Although there are currently no forecast models that can effectively predict meteotsunamis in the United States, new research from NOAA based on the Ludington wave shows that numerical weather prediction models and hydrodynamic forecast models existing NOAA’s can allow scientists to predict these atmospheric waves causing meteotsunamis from minutes to hours. advanced. The research is published in a special edition of the journal Natural hazards about meteotsunamis.

“The good news with this type of meteotsunami is that it is easier to predict than those triggered by thunderstorms,” ​​said Eric Anderson, oceanographer at NOAA’s Great Lakes Environmental Research Laboratory and lead author of the study. . “Our short-range weather models can pick up these atmospheric pressure waves, while prediction of thunderstorms is more difficult.”

Meteotsunamis are a lesser-known category of tsunami. Unlike the more well-known tsunami – such as the catastrophic Boxing Day tsunami in Indonesia, which was caused by an earthquake on the seabed, meteotsunamis are caused by weather conditions, in particular a combination of changing air pressure, strong winds and thunderstorms.

“Because lakes are relatively small, meteotsunamis generally need more than a simple jump in air pressure to train them,” Anderson said. “This is where thunderstorms and wind come in to push them.”

The Great Lakes have a history of meteotsunamis

Meteotsunamis are found throughout the world and are known in the United States primarily on the Great Lakes and along the eastern coasts and Gulf of Mexico. Meteotsunami waves in the Great Lakes can be particularly insidious, as they can bounce off the shore and return when the skies are clear. They are relatively rare and usually small, with the larger ones producing waves of three to six feet, which only occur once every 10 years.

Predicting these waves in advance would give communities potentially life-saving warnings and allow residents and businesses to take action to better protect property. Ludington’s meteotsunami caused property damage but not serious injury. If the meteotsunami had struck in the summer when swimmers, fishermen and vacationers flock to the beaches, parks and lakeside waters, it might have been a different story, as it did with a meteotsunami that cost the lives of eight people in Chicago in June 1954..

“It’s a gap in our forecast,” Anderson said. “With this study and other research, we are getting closer to the ability to predict them in advance.”