Conditional instability of the second kind

From Glossary of Meteorology

conditional instability of the second kind

(Abbreviated CISK.) A process whereby low-level convergence in the wind field produces convection and cumulus formation, thereby releasing latent heat.

This enhances the convergence and further increases convection. The atmospheric environment that favors CISK is found over warm, tropical oceans where there is an abundant supply of moisture, the Coriolis force is small, and air convergence is strong.

Charney, J. G., and A. Elliasen 1964. On the growth of the hurricane depression. J. Atmos. Sci.. 21. 69–75.