Static stability variations during the development of an intense extratropical cyclone

The role of static stability (sigma) is diagnosed for an intense extratropical cyclone that developed over the central United States during January 9-11, 1975. Results indicate that minimum sigma values occurred in the lower troposphere at 0000 UTC January 10, 1975, during the period of slow cyclone development, and then increased as rapid development proceeded. Further, the upward advection of smaller static stabilities in the cyclone area, a forcing process in the height tendency equation, resulted in a significant reduction of height falls attributed to vorticity advection, thermal advection, and latent heat release.