A meteotsunami is a coastal wave generated by rapid changes in atmospheric pressure, strong winds, or other weather disturbances. Unlike a tsunami caused by an underwater earthquake, volcanic eruption, or landslide, a meteotsunami begins in the atmosphere. As a moving weather system transfers energy to the ocean, it can create waves that grow larger as they approach the shore, sometimes producing sudden flooding, powerful currents, and dangerous water-level changes.
Meteotsunamis can occur along coastlines around the world, including the Great Lakes and the Atlantic, Pacific, and Gulf coasts of the United States. They can develop during thunderstorms, squall lines, and other fast-moving weather systems. Although some produce only modest fluctuations in water level, others can be powerful enough to sweep people off piers, inundate waterfront areas, and damage boats and coastal infrastructure.
Understanding how these waves form requires looking beyond the ocean itself. The atmosphere and the sea are closely connected, and under the right conditions, a relatively small atmospheric disturbance can trigger a much larger movement of water.
How a meteotsunami differs from an ordinary tsunami
The most important difference between a meteotsunami and a conventional tsunami is what initiates the wave.
A geological tsunami typically begins when a large volume of water is displaced by an underwater earthquake, a landslide, or another sudden disturbance of the seafloor or water column. The resulting waves can travel across entire ocean basins while carrying energy through the water.
A meteotsunami, by contrast, is generated by atmospheric forcing. Rapid pressure changes and strong winds associated with weather systems transfer energy to the water, producing long waves that can behave much like earthquake-generated tsunamis once they are established.
The two types of waves can share important physical characteristics. Both may have wavelengths much longer than the depth of the water and can travel at speeds governed largely by water depth. Both can also become more hazardous as they enter shallow coastal waters, where the seafloor influences their speed, height, and shape.
The term meteotsunami combines meteorological, referring to weather and atmospheric processes, with tsunami, referring to a series of long waves that can cause substantial coastal water-level changes. The name describes the wave’s atmospheric origin without implying that its effects are necessarily small.
Meteotsunamis are also distinct from storm surge. Storm surge is an abnormal rise in coastal water level driven primarily by persistent winds and low atmospheric pressure over a broader area, often during a tropical or extratropical storm. A meteotsunami involves a wave-like disturbance that can produce rapid fluctuations in water level over minutes to hours. The processes can occur together, and distinguishing them may require examining the timing and characteristics of the water-level changes.
How atmospheric disturbances generate ocean waves
The formation of a meteotsunami depends on how quickly the atmosphere changes and how effectively that change transfers energy into the ocean.
One mechanism involves a rapid change in atmospheric pressure. The ocean surface responds to the weight of the air above it. When atmospheric pressure decreases, the water surface tends to rise slightly; when pressure increases, the surface tends to fall. This response is sometimes called the inverted barometer effect.
Under ordinary circumstances, these pressure-driven changes are relatively small. A brief pressure disturbance, however, can do more than produce a simple rise or fall in sea level. If it moves across the water at a speed that matches the speed of a long ocean wave, it can efficiently transfer energy to the water and amplify the disturbance.
Strong, rapidly changing winds provide another source of energy. Wind can push water toward a coastline, move it away from shore, or generate a moving disturbance that develops into a long wave. The precise outcome depends on the wind’s direction, strength, duration, and movement, as well as the shape and depth of the water body.
Atmospheric pressure changes and wind forcing often occur together. For example, a fast-moving line of thunderstorms may contain sharp pressure variations, powerful gusts, and abrupt changes in wind direction. As the system crosses a lake or coastal region, these disturbances can set the water in motion.
The resulting wave may initially be difficult to distinguish from ordinary fluctuations. Its danger depends on whether the atmospheric disturbance continues to supply energy, how the wave travels through the water, and what happens when it reaches the coast.
Why the speed of a weather system matters
A crucial ingredient in many meteotsunamis is a process called resonance. In this context, resonance occurs when a moving atmospheric disturbance travels at approximately the same speed as a long wave in the water. The match allows energy to accumulate in the wave rather than being transferred inefficiently.
For a long wave in water that is shallow relative to its wavelength, the wave speed can be approximated by:
c = √(g × h)
Here, c is the wave speed, g is the acceleration due to gravity, and h is the water depth. The equation shows that long waves generally travel faster in deeper water and slower in shallower water.
Because water depth varies among lakes, bays, shelves, and coastal zones, the speed required for resonance varies as well. A weather system that moves too quickly or too slowly for the local conditions may generate only a limited response. If its speed closely matches the speed of the water wave, the resulting amplification can be much greater.
This process is known as Proudman resonance, named after the scientist who analyzed the amplification of long waves by moving atmospheric disturbances. It is an important mechanism in meteotsunami formation, although not every meteotsunami requires the same combination of atmospheric and oceanic conditions.
The disturbance must also have an appropriate structure and duration. A weather system that passes over the water too briefly, or whose pressure and wind patterns are poorly suited to wave generation, may not transfer enough energy to create a significant coastal hazard.
Resonance therefore helps explain why not every thunderstorm produces a meteotsunami and why similar-looking weather systems can have very different effects on the water.
How a small disturbance can become a dangerous coastal wave
A meteotsunami does not need to begin as a towering wall of water. Its initial disturbance may be relatively modest, but local geography and changing water depth can increase its impact as it approaches shore.
As a long wave enters shallower water, its speed decreases. Under suitable conditions, its height increases as its energy becomes concentrated into a smaller water column. This process is called shoaling, and it is also important in the behavior of conventional tsunamis.
The shape of the coastline and the underwater landscape can further alter the wave. Continental shelves, bays, harbors, narrow inlets, and other features can redirect wave energy or concentrate water movement. Some locations can support natural oscillations that amplify the response to an incoming disturbance.
A particularly important process is harbor resonance. A bay or harbor can oscillate at certain natural periods, much as water sloshes back and forth in a bathtub. If incoming waves repeatedly stimulate one of these oscillations, water levels and currents inside the harbor may grow stronger even after the original atmospheric disturbance has passed.
In some locations, the interaction between a moving disturbance and the local geography can produce rapid changes in water level. Water may surge toward shore, retreat unusually far, or oscillate repeatedly between high and low levels.
These effects help explain why the same meteotsunami can produce different outcomes along a single coastline. One harbor may experience strong currents while a nearby beach sees a smaller water-level change. The severity depends not only on the incoming wave but also on local bathymetry, shoreline geometry, and the timing of the disturbance.
What weather conditions can produce a meteotsunami?
Meteotsunamis are most closely associated with atmospheric disturbances that move rapidly and produce substantial pressure or wind changes over water.
Thunderstorms are one potential source, particularly when organized into squall lines or other coherent systems. Their gust fronts and pressure disturbances can move across lakes and coastal waters, transferring energy into long waves.
Fast-moving cold fronts and other atmospheric boundaries can also generate the necessary conditions. Rapid pressure changes associated with these systems may create a moving disturbance that interacts with the water, especially when its speed aligns with the speed of long waves in the affected region.
Some meteotsunamis occur during otherwise ordinary-looking weather conditions. The relevant atmospheric disturbance may be brief or localized, and the wave’s development depends on the relationship between the weather system, the water depth, and the coastline. Severe weather is not a prerequisite in every case.
Nor does a major storm automatically produce a meteotsunami. Many storms generate storm surge, wind-driven waves, or ordinary changes in water level without creating a distinct meteotsunami. The atmospheric disturbance must transfer energy to the ocean in a way that supports the formation and propagation of a long wave.
The most favorable conditions can be difficult to recognize from a general weather forecast alone. A forecast may correctly predict thunderstorms or strong winds without identifying whether those systems will generate a significant coastal wave.
Where meteotsunamis occur in the United States
Meteotsunamis can develop wherever atmospheric disturbances interact with suitable bodies of water. In the United States, they have been observed in the Great Lakes and along ocean coastlines, including the Atlantic and Gulf coasts.
The Great Lakes are especially relevant because they are large enough for long waves to travel considerable distances, yet their enclosed geography differs from that of the open ocean. Atmospheric disturbances crossing a lake can generate waves that interact with the lake’s depth, shoreline, and bays. The resulting water-level changes can be hazardous around beaches, marinas, and other exposed waterfront areas.
On the Atlantic coast, meteotsunamis may affect beaches, estuaries, bays, and harbors. Coastal geometry can make certain locations particularly responsive to incoming waves, even when the broader region experiences relatively modest water-level changes.
The Gulf Coast also provides suitable conditions for atmospheric wave generation, particularly where shallow coastal waters and complex shorelines influence the movement of long waves.
The risk is not uniform across these regions. Local depth, coastline shape, weather patterns, and the characteristics of individual water bodies all influence whether a meteotsunami forms and how strongly it affects a particular location.
Meteotsunamis are not limited to the United States. They have been documented in many parts of the world, demonstrating that the atmosphere-ocean interactions responsible for them are widespread rather than unique to one coastline or climate.
Why meteotsunamis can be difficult to predict
Predicting a meteotsunami requires more than identifying potentially favorable weather. Forecasters must also understand how the atmospheric disturbance will interact with the water and how the resulting wave will respond to local coastal conditions.
The first challenge is atmospheric. Small differences in a weather system’s speed, direction, pressure pattern, and wind field can affect how efficiently it transfers energy to the water. Weather forecasts may capture the general movement of a storm while missing details that determine whether resonance will occur.
The second challenge is oceanographic. Water depth, underwater topography, and the natural oscillation periods of bays and harbors influence wave propagation and amplification. These factors can cause a wave to grow in one location and remain comparatively weak in another.
The third challenge is detection. A meteotsunami may resemble ordinary water-level fluctuations caused by wind, tides, or other processes. Recognizing it can require comparing measurements from tide gauges or lake-level monitoring stations with records of atmospheric pressure, wind, and the timing of the disturbance.
Forecasting and warning systems can use these observations alongside weather models and knowledge of vulnerable coastal areas. However, predicting the exact height and timing of a meteotsunami at a particular shoreline remains difficult because the atmospheric and oceanic processes must be understood together.
This uncertainty does not mean that meteotsunamis are impossible to anticipate. It means that reliable warnings depend on identifying favorable atmospheric conditions, monitoring water-level changes, and accounting for local coastal responses.
The hazards meteotsunamis pose to people and infrastructure
The danger of a meteotsunami comes from both the movement of water and the speed with which conditions can change.
A sudden rise in water level can flood low-lying waterfront areas, overtop exposed structures, and carry water onto beaches or walkways. A rapid retreat can expose areas that were recently underwater, potentially drawing people toward the water just before another surge arrives.
Strong currents can be especially hazardous in harbors, channels, marinas, and near piers. Even when the change in water level appears small, rapidly moving water can destabilize swimmers, move small boats, damage moorings, and create dangerous conditions around structures.
Repeated surges may compound the problem. A meteotsunami can consist of a series of waves or oscillations rather than a single event, and the water may continue moving back and forth after the first noticeable change. A brief period of calm therefore does not necessarily mean that the hazard has ended.
The effects also depend on the surrounding conditions. A meteotsunami coinciding with high tide or elevated coastal water levels can produce greater flooding than the same wave arriving when water levels are lower. If it occurs during a thunderstorm, lightning, high winds, and poor visibility may add further risks.
Not every meteotsunami causes substantial damage, and many produce only limited water-level fluctuations. The concern is that the more dangerous events can develop rapidly, with little obvious warning to people standing near the water.
How to recognize and respond to a possible meteotsunami
A meteotsunami may not have a distinctive appearance from shore. It can arrive without the large breaking waves people commonly associate with tsunamis, and its first sign may be an abrupt change in water level or unusually strong currents.
A sudden, unexplained surge or retreat of water, rapid fluctuations around a marina, or strong currents that develop unexpectedly should be treated as a potential hazard rather than an invitation to investigate. Such changes can have several causes, and it may not be possible to identify a meteotsunami immediately.
People near beaches, piers, harbors, and lakefronts should move away from the water if they observe unusual and rapid changes in water level or currents. They should not enter exposed areas to retrieve equipment or approach the shoreline to watch the event. Official weather alerts, local emergency instructions, and guidance from relevant authorities should take priority.
Boaters and marina users should be particularly cautious when atmospheric conditions are changing rapidly. Unexpected currents and repeated water-level fluctuations can strain mooring lines, move vessels, and make navigation difficult in confined waters.
Preparedness also depends on understanding local hazards. Coastal and lakeside communities can reduce risk by identifying vulnerable low-lying areas, maintaining water-level monitoring equipment, and developing procedures for communicating warnings quickly.
Because meteotsunamis may develop over a short period, public awareness is an important part of safety. Recognizing that dangerous coastal waves can originate from weather—not only from earthquakes—helps people respond appropriately to sudden water-level changes.
What meteotsunamis reveal about the atmosphere and the ocean
Meteotsunamis demonstrate that the ocean does not respond only to forces originating beneath or within the water. Atmospheric pressure and wind can generate waves, and the effects of those waves depend on interactions among weather, gravity, water depth, and coastal geography.
Their behavior also illustrates why coastal hazards cannot always be understood by examining a single process in isolation. A modest atmospheric disturbance may generate a small wave offshore, but resonance can amplify it during formation, and local geography can increase its impact near shore. The final hazard emerges from the combined behavior of the atmosphere and the ocean.
Meteotsunamis remain challenging to predict precisely, but the underlying physics is well established. Rapid atmospheric changes can transfer energy into long waves, matching the speed of the disturbance to the wave speed can increase that transfer, and shallow water and coastal features can further influence the result.
Recognizing these connections improves understanding of sudden coastal water-level changes and supports more effective monitoring, forecasting, and public safety. A wave generated by weather may be less familiar than one generated by an earthquake, but under the right conditions, it can be just as important to understand.
