Bred Vectors (BVs) are computed as follows: 1) Start with an arbitrary initial perturbation                 of size A defined with an arbitrary norm. This initialization step is executed only once. The size is essentially the only tunable parameter of breeding. 2) Add the perturbation to the basic solution, integrate the perturbed initial condition with the nonlinear model, and subtract the original unperturbed solution from the perturbed nonlinear integration: 3) Divide the perturbation by the measured amplification factor so that its size remains equal to A: