Persistence of hydrodynamic envelope solitons: detection and rogue wave occurrence

Abstract: The observation of a wave group persisting for more than 200 periods in the direct numerical simulation of nonlinear unidirectional irregular water waves in deep water is discussed. The simulation conditions are characterized by parameters realistic for broad-banded waves in the sea. The group is identified by the solution of the associated scattering problem for the nonlinear Schr\"odinger equation as the intense envelope soliton with remarkably stable parameters. Most of extreme waves occur on top of this group, resulting in higher and longer rogue wave events.