Notes on the theory of tropical cyclones

The conditions under which continued outward motion is possible in a circular vortex are investigated theoretically, and the results applied to the development of tropical cyclones, in order to give a possible explanation of the removal of air from the storm centre and the associated fall of pressure. The development of a storm by this mechanism is described and necessary conditions for such development are found to be:—( a ) A lapse rate which will give rise to vertical instability and development of convection cloud. ( b ) A distribution of circulation at some level aloft such that anticyclonic circulation increases outward at a rate exceeding a certain value. ( c ) A distribution in the vertical of horizontal rotation such that cyclonic circulation decreases with height. The importance of horizontal turbulence in producing the calm “eye” of the storm is considered, and the relation between tropical cyclones and fronts is briefly discussed.