Bred vectors are constructed as finite amplitude, finite time approximations of Lyapunov vectors. The fact that we use them locally, rather than globally, greatly reduces the number of independent bred vectors needed (Kalnay et al, 2002). Since the bred vectors represent the instabilities of the underlying flow, and these are finite time, finite space, it is reasonable to assume that there may be instabilities that the bred vectors “miss” if they are confined to a too small subspace. Therefore, “sprinkling” bred vectors with small random perturbations not only mimics observational errors but keeps them “young” and gives them a better chance to represent new instabilities that may appear in the analysis errors.