Why can ship wakes appear narrower than Kelvin’s angle?

An elementary analysis of interference between the divergent waves created by the bow and the stern of a monohull ship, of length LsLs, that advances at constant speed VsVs along a straight path in calm water of large depth shows that the largest waves created by the ship hull are found at an angle ψmaxψmax (measured from the path of the ship) that is smaller than the Kelvin wake angle ψK≈19∘28′ψK≈19∘28′ if the Froude number F≡Vs/gLs is larger than FK≈0.59FK≈0.59. Interference between transverse and divergent waves created by the bow and the stern of a monohull ship also yields large waves at angles that can be significantly smaller than ψKψK for F