Arches of Clouds as Precursors of Thunderstorms

Abstract

Satellite photographs of 5 May 1983 show arches of clouds over Nebraska and Kansas that resemble clouds on the outflow boundaries near thunderstorms. However, there were no thunderstorms to provide the outflow. The arches were found to have formed along gravity waves in the southerly low-level flow. Larger thunderstorms formed later at the west ends of the gravity waves where the convergence in the low levels was enhanced by interaction with westerlies in the environment.