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Spooked By A Meteotsunami

To test a raincoat, I deliberately walked headlong into a downpour across an expansive Florida beach. When I reached the water, a lone pelican floated easily on the 2-foot chop straight ahead while a cluster of shore birds weather-vaned on land. I turned south and accepted wind-driven rain on my starboard cheek, walking casually above the foamy surf that defined the typical water's edge.


After only a few steps and without warning, a singular wave failed to retreat. The water slowly rose up, first soaking my feet, then rising knee-high to fill the inside of my rain pants, far from the leg protection I had been expecting. The startling surge behind the wave front had the strength of a strong undertow, and I crouched to brace against the rapid inflow. Regaining footing, I watched (and felt) the saltwater push unimpeded across another 300 feet of flat beach. I found myself suddenly wading knee-deep far from dry land.


That rising volume of water--perhaps three feet from the extant water level of the floating pelican up to my submerged knees--demarcated its forward advance with a debris line. Soon I felt the column of water within my rain pants drop below my calves, and the vast ephemeral pond retreated in broad sheets of water and rivulets back to the gulf.


Water across broad flat beach.
Several minutes after a meteotsunami made landfall, retreating water still covers a beach hundreds of feet from the shoreline.


Trodding through ankle-deep water several minutes later, as the downpour abated I took a photo of the beach and grabbed a radar screenshot. I wondered who might have noticed the rise and fall of a long lone wave while sheltering in their hi-rise perches.


Radar image from 9:21 pm on Feb. 4, 2024.
Radar shows line of strong storm paralleling curved shoreline. Image: Weather Underground.

I initially thought the phenomenon had been a seiche, so I was excited for three reasons--first was the mere alarm of the inundating wave; second, it would have been a big seiche for anyone, and certainly the biggest in my life; and third, I like the word seiche. Confirmation bias argued in its favor. I messaged a friend, suggesting babies would have been washed out to sea had the beach been crowded.


However, the alternative meteotsunami explanation gained traction after I remembered I had written a blog post Beware of Lake Michigan Freaks in May 2019:


Two freaks on Lake Michigan may not be so rare after all.  Weather phenomena known as seiches and meteotsunamis give rise to sudden waves that are capable of washing beachgoers out to sea. In a recent article in the Chicago Tribune, scientists suggests the surging wave that suddenly killed eight Chicagoans in 1954 can be blamed on a meteorological tsunami.  Though such a rogue wave occasionally builds up six to eight feet, as in 1954, smaller yet still-dangerous versions typically occur up to two dozen times per year on Lake Michigan.  Some drownings previously attributed to recklessness on a pier, for example, may now be viewed as weather-induced tragedies.

 

In introducing meteorological tsunamis, the article distinguishes between the two related events:

Seiches and meteotsunamis are both caused by spikes in air pressure and driving winds, which cause water to pile up as a storm moves across a lake. But they differ in size and time-span. A seiche is a singular lakewide wave rocking back and forth while a meteotsunami is generally the width of a storm front and lasts for a shorter period of time.

Seiches, which can flood coastal areas for several hours, are frequently compared to water sloshing back and forth in a bathtub. A meteotsunami, on the other hand, has been described as being similar to the effect of running one’s hand across the surface of water in a bathtub.

 

Previously, seiches had been deemed the culprits in shoreside inundations.  Jonathan Selbig tallied past  similar events that include descriptions of boats in harbors being bashed about.  A photograph at the New Buffalo Railroad Museum depicts a 1900's waterfront scene with men and women casually in rowboats with people and horses crossing a wooden bridge in the background.  The caption states, "This bridge is thought to be the one that was destroyed by the 'Great Wave' in 1908."  

Early 1900's photo of wooden footbridge and rowboats.
Image courtesy New Buffalo Railroad Museum.

On the Fourth of July, 1929, ten people died in Grand Haven, MI, and in 1938 five people were claimed by a wave in Holland, MI, on a calm day.  More recently, again on the Fourth of July, in 2003, seven people died on lower Lake Michigan within four hours after a storm blew through.  In hindsight, some of these events may be attributed to meteotsunamis.  


A 2012 Berrien County document on past historical disasters cites two past waterside events, from 1893 and 1960. Of the April 7, 1893, phenomenon it states:

Described as a “tremendous tidal wave”, water swept in from Lake Michigan in St. Joseph about 9:00PM. The water extended over the beach 600 to 700 feet. Water in the St. Joseph River rose to a height of four or five feet above normal. The big wave swept away every moving thing before it and receded within a few minutes. Remarkably, there was no rough weather on the lake at the time.

 

The forces of nature can be on full display, such as in the midst of a raging thunderstorm, or subtle and sudden, such as in the proverbial but very real bolt out of the blue.  Similarly, outside the presence of a storm at the beach there can lurk a seiche or meteotsunami, yielding a rapid inundation of high water and increased rip currents.  Consider it one more reason to respect the power of the Great Lakes.  


On Feb. 4, 2024, around 9:30 a.m., I experienced a startling but memorable meteotsunami along a curved shoreline with a broad flat beach. A unique wave generated by high wind speeds and/or a quick change in air pressure overtook my seemingly safe position on shore. While standing knee-deep surrounded by water in a driving rain, I at least found comfort in a new realization--the rain coat worked.



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