he Kelvin-Helmholtz (KH) instability is one important source of turbulence in stably stratified fluids (such as the atmosphere). Attempting to characterize the turbulence that results from KH events forces us to consider the problem of finding "optimal perturbations" to KH flow. This amounts to finding the initial condition that, under the action of a flow, grows the most, relative to some norm. This can then be further reduced to a simple problem in linear algebra: finding the eigenvectors of an Hermitian matrix.