Numerous cold fronts associated with mature extratropical storms sweep the coast of Chile every year. The large expanses of the Southern Pacific Ocean offer an ideal setting for up to 4000-km long cold fronts to develop as their parent cyclones travel from Australia to South America. These fronts sometimes break and spawn secondary cyclones that deepen significantly in one or two days. Examples of such frontal waves will be shown and discussed. An attribution technique applied to scatterometer wind measurements is used to diagnose the development of those frontal waves. Necessary conditions for their development are revealed