Abstract
The following stability criterion of a motion of a circular vortex embedded in a geostrophic general current is evaluated by means of the parcel method, i. e.:
where RN is the Richardson Number, λ the Coriolis parameter and υθg, the tangential component of a geostrophic general current. This stability criterion is evaluated for the case that the cyclonic circulation of circular vortex develops.
This shows that the conditions for the formation of tropical cyclones can be described as the combined effect of the vertical shear and the static and dynamic stability. It is emphasized that the barotropic state of the upper atmosphere is very favorable for the formation of tropical cyclones in the atmosphere of static instability. An example on August 1950 is also discussed.
