Abstract: In this paper the process how an unstable growing disturbance stops developing is investigated. The main mechanism to check the development is the feeding-back effect of the unstable disturbances on the basic current. It is shown that the time elapsed for an unstable.disturbance to grow to its maximum intensity is roughly proportional to its initial amplitude. For an amplitude of 100 meters the time is about 8 days, and that for an amplitude of 200 meters is about 5 days. Further, in the vorticity and thermo- dynamic equations we keeped the non-linear terms which are generally dropped. This enables us to study the mutual interaction of the disturbances. It is shown theoretically that this mutual interaction is important in the formation of Ω-shaped blocking highs.