Predicting the occurrence of rogue waves in the presence of opposing currents with a high-order spectral method

We discuss the dynamics of unidirectional random wave fields that propagate against an opposing current through laboratory experiments and direct numerical simulations of the Euler equations solved with a high-order spectral method. Both approaches demonstrate that the presence of a negative horizontal velocity gradient increases the probability of the occurrence of extreme and rogue waves in the course of their propagation with the emergence of a rapid transition from weakly to strongly non-Gaussian properties. Numerical simulations capture quantitatively well the statistical properties of laboratory observations and substantiate that underlying physics are associated to quasiresonant nonlinear interactions triggered by the background current.