The polar low as an extratropical CISK disturbance

It is suggested that the polar low is basically a thermal instability phenomenon much akin to a small tropical cyclone. A quasi‐geostrophic model is employed in order to find small‐scale unstable CISK‐forced disturbances in a barotropic basic flow with a vertical structure similar to that actually observed during a polar air outbreak. Case studies of some polar low developments in some ways support a convective hypothesis according to which the polar low is driven by latent heat released in convection clouds.