Fig. 3: Evolution of summary parameters of the focused irregular waves (Wave Category II) shown in Figs. 2 and 4.

a Evolution of the norm N/N0 b Evolution of the mean frequency Ωc. Note that Ω = 0 corresponds to the central peak of the initial spectrum, which is lower than Ωc for the initial condition. c Evolution of the characteristic steepness \({\eta}_{\max }{k}_{0}\).