Measuring a rogue? An investigation into an apparent giant wave

TL;DR

This study critically examines a reported giant wave event using statistical, kinematic, and numerical analyses, concluding it was likely a false event rather than a real rogue wave.

Contribution

It introduces a comprehensive forensic methodology to assess the plausibility of reported rogue wave events, combining statistical, kinematic, and numerical approaches.

Findings

The event was incompatible with known wave behavior.

Numerical reconstructions failed to replicate the event.

Analysis suggests the event was not a real wave.

Abstract

An apparent giant wave event having a maximum trough-to-crest height of 21 metres and a maximum zero-upcrossing period of 27 seconds was recorded by a wave buoy at a nearshore location off the southwestern coast of Australia. It appears as a group of waves which are significantly larger both in height and period than the waves preceding and following them. This paper reports a multifaceted analysis into the plausibility of the event. We first examine the statistics of the event in relation to the rest of the record, where we look at quantities such as maximum-to-significant wave height ratios, ordered crest-trough statistics, and average wave profiles. We then investigate the kinematics of the buoy, where we look at the relationship between the horizontal and vertical displacements of the buoy, and also attempt to numerically reconstruct the giant event using Boussinesq and nonlinear shallow water equations. Additional analyses are performed on other sea states where at least one of the buoy's accelerometers reached its maximum limit. Our analysis reveals incompatibilities of the event with known behaviour of real waves, leading us to conclude that it was not a real wave event. Wave events similar to the one reported in our study have been reported elsewhere and have sometimes been accepted as real occurrences. Our methods of forensically analysing the giant wave event should be potentially useful for identifying false rogue wave events in these cases.