New satellite observations show that one remote storm in late 2024 generated waves as tall as an 11‑storey building, hurling energy across entire oceans and forcing scientists to rethink how dangerous swells travel, grow and impact distant coastlines.
When a far‑off storm sends walls of water around the globe
At the end of 2024, a powerful storm nicknamed Eddie spun over the North Pacific, hundreds of kilometres from land. Ships avoided its core, and the system never made the kind of landfall that grabs headlines. Out at sea though, it produced something extraordinary.
Average wave heights exceeded 19 metres, according to a team led by French oceanographer Fabrice Ardhuin. Within that turbulent sea, individual waves likely climbed to around 35 metres from trough to crest. That is close to the height of Big Ben’s clock faces stacked on top of each other.
These giant waves travelled roughly 24,000 kilometres, crossing from the North Pacific, through the Drake Passage, and into the tropical Atlantic.
In surf spots like Hawaii and parts of California, the same swell powered legendary big‑wave competitions such as the Eddie Aikau Invitational. On the beach, it looked like a spectacular gift for surfers. For researchers, it became a rare full‑scale experiment offered by nature.
Unlike hurricanes that smash directly into coasts, Eddie’s main impact was remote. It launched long, powerful swell that rolled silently across basins for days, conserving a surprising amount of energy as it went. That ability to project force far beyond the storm’s footprint is now under the microscope.
How Eddie ranks among the fiercest recent storms
Ardhuin’s group compared Eddie’s waves with those generated by Hercules, a notorious 2014 storm that hammered Atlantic coasts from Morocco to Ireland. Based on satellite data from the European Space Agency, Eddie’s swell appears comparable to, and sometimes stronger than, Hercules.
What makes Eddie stand out is not only the size of the waves, but the length of their journey and the precision with which they were measured. Until recently, scientists relied heavily on models and sparse buoys. This time, they had a new eye in the sky.
What satellites are suddenly revealing about giant waves
For decades, ocean models have tried to capture how storms generate waves and how that energy spreads. But direct observations far from land were rare. That changed with SWOT, the Surface Water and Ocean Topography satellite, a joint mission by NASA and the French space agency CNES.
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SWOT is designed to map sea surface height with high resolution. For wave scientists, that means they can finally track long, ocean‑spanning swells with far better accuracy, including waves with more than 500 metres between crests.
SWOT’s measurements in December 2024 confirmed that very long‑period waves, with up to 30 seconds between crests, carry more focused and punchy energy than expected.
Earlier empirical formulas tended to smear that energy across a broad range of waves. In practice, the team found, the energy is concentrated into a handful of dominant waves, like a fighter saving power for a few heavy blows instead of lots of jabs.
The findings, published in Proceedings of the National Academy of Sciences in 2025 by Ardhuin and colleagues Quentin Postec and Jérôme Accensi, support a fresh way to describe extreme wave fields. Their work takes into account non‑linear interactions between short, choppy waves and the longer swells passing underneath, a complexity many older models set aside.
A new way to “read” the sea surface
The study suggests that simply looking at average wave height or standard wave period misses key dangers. A seemingly normal sea state can hide a train of long‑period waves packing disproportionate force.
- Short waves tend to break near the surface and lose energy quickly.
- Long‑period waves can travel thousands of kilometres with limited loss.
- When they reach shallow waters, they stand up into tall, steep breakers.
By combining SWOT’s precise measurements with refined spectral models, forecasters gain a sharper picture of which storms will send hazardous swells to which coastlines, and on what timescale.
Coastal futures in a more energetic ocean
The implications reach far beyond academic curiosity. Long‑range swells like those from Eddie can shape coastlines, unsettle ports and catch coastal communities off guard even when the sky overhead is blue.
Long‑period waves can dramatically increase coastal erosion and wave run‑up, in some cases overtopping sea walls designed around older, weaker estimates.
Engineers rely on design waves when planning harbours, breakwaters, offshore platforms and wind farms. If the true energy of these extreme swells has been systematically underestimated, those standards may need updating, especially at exposed Atlantic and Pacific sites.
Ardhuin’s team points out that local factors still matter a great deal. The shape of the seabed, underwater canyons and the orientation of the coastline can either focus or diffuse incoming swell. Two towns a few kilometres apart may face very different risks from the same distant storm.
Climate change: are extreme swells becoming more common?
The research does not claim that climate change has already increased the number of Eddie‑style storms. Scientists are cautious on this point. Nonetheless, they are running new simulations to see if warming oceans and shifting wind patterns are nudging storm tracks and intensities in ways that favour stronger, more organised wave fields.
Some climate models suggest that in certain basins, the most intense storms could become more frequent or migrate into new regions. If that happens, coastlines that historically saw modest swell might experience more long‑period waves, testing ageing defences and infrastructure.
From rogue waves to “silent” hazards
The study also connects to a broader effort to understand dangerous, unusual waves at sea. Mariners often talk about rogue waves: rare, steep walls of water that seem to rise from nowhere. While Eddie’s waves belong to a different category, both phenomena sit inside the same physics of non‑linear wave interaction.
By mapping full wave spectra from space, missions like SWOT can help identify the conditions where large, unexpected peaks are more likely. That may one day feed into ship routing systems, reducing the risk of structural damage or cargo loss on key trade routes.
Another practical spin‑off sits underground. Long swells can shake the seabed and register on seismometers as “microseisms” – a kind of constant background humming of the planet. Better knowledge of remote wave trains makes it easier for geophysicists to separate this ocean noise from genuine tectonic signals.
Key terms that sharpen the picture
A few technical expressions keep coming up in this research, and they shape how risk is judged:
| Term | What it means | Why it matters |
|---|---|---|
| Significant wave height | Average height of the highest one‑third of waves | Standard measure used in forecasts and engineering design |
| Wave period | Time between two crests at a fixed point | Longer periods often mean deeper, more powerful waves |
| Swell | Waves generated by distant storms, travelling far from their source | Can impact coasts even when local winds are light |
| Spectral model | Model that describes how wave energy is distributed over periods and directions | Core tool for predicting coastal and offshore wave conditions |
What this means for people living by the sea
For coastal residents, the idea that a storm thousands of kilometres away can reshape a beach or damage a harbour still feels counter‑intuitive. Yet the Eddie case provides a clear, measured example.
In practice, better swell forecasts can support early warnings for:
- Harbour operations, such as scheduling cargo handling and ferry services.
- Coastal road closures in low‑lying zones prone to wave overtopping.
- Big‑wave surfing events that depend on rare, intense swells.
- Offshore maintenance campaigns for wind farms and oil platforms.
City planners and insurers are also paying attention. As flood and erosion maps get updated, accounting for longer‑range, high‑energy swells could alter zoning rules, insurance pricing and the design of new sea defences.
The satellites will not stop the next Eddie, but they give scientists and coastal communities a clearer view of what is rolling toward them, long before any white water meets the sand.
Originally posted 2026-03-11 09:16:40.