On the Decay of Supercells through a "Downscale Transition": Visual Documentation

Photographic and mobile-radar documentation of the dissipation of a supercell and a severe convective storm that had not yet developed into a mature supercell are discussed. It is hypothesized, based on these cases and on others, that when a low-precipitation or classic supercell and/or a developing supercell moves into an environment of cooler surface temperatures and a strong capping inversion, it eventually dissipates through a process of "downscale transition," in which vertical shear tilts the updraft more in the downshear direction as the CAPE decreases, and the updraft becomes narrower as the storm dissipates. During the downscale transition, it is possible that a cold pool or lack thereof may play a role, but the documentation in the cases detailed herein is not adequate to address this issue.