This article is hard to read, like most media outlets these days. Why do they run so many scripts, that call other scripts, that call other scripts...? Here's the nutshell anyway, via Firefox + NoScript + Ublock Origin and selectively blocking certain elements:
> "Scientists have since figured out that unlike tsunamis, which are large waves produced by a sudden displacement of water from an event such as an earthquake or landslide, rogue waves form due to a chance combination of wave movements through the ocean."
> "Two main mathematical theories have emerged to explain the wave movements that spawn rogue waves: Linear addition and nonlinear focusing. Linear addition assumes that waves travel through the ocean at different speeds, and when they overlap, they can strengthen into a rogue wave. Nonlinear focusing assumes waves travel in groups and can lend energy to one another, which sometimes spawns a rogue wave."
> "One reason for the uncertainty is that rogue waves are rare. Even now, there’s a dearth of quality tracking data."
For those not at sea in a boat, but walking along a coastline, the practical thing to keep in mind is that just because the ground is dry, doesn't mean a sneaker wave can't come along once an hour, so be careful and keep your eyes on the ocean.