The onset of blocking and cyclogenesis in Southern Hemisphere synoptic flows: linear theory.

A study is made of the instability of two instantaneous Southern Hemisphere synoptic flow fields. The growth rates, phase frequencies, perturbation streamfunctions and for some modes, eddy heat and momentum fluxes of growing disturbances are obtained using a linear, spherical, five-level, quasi-geostrophic model. Both the zonally averaged and three-dimensional flow fields are studied and the eigenmodes are compared with the observed regions of the onset of blocking and of developing midlatitude cyclones.-from Author