The formation of multiple fronts

Using two‐dimensional semi‐geostrophic frontogenesis models and three‐dimensional semi‐geostrophic baroclinic wave models, it is shown that atmospheric development in the presence of non‐uniformities in pre‐existing temperature distributions may be expected to lead to the frequent occurrence of multiple frontal structures. In general, such non‐uniformities in the temperature distribution will be important if they significantly change the ambient temperature gradient. The frontal structures associated with the irregularities tend to be very shallow. They are possible candidates for the triggering mechanism for frontal troughs well behind a cold front and for shallow rainbands ahead of such a front. However, it seems that a separate mechanism is still necessary for the production of the middle‐level banded structures that are frequently observed.