Resonance trough

From Glossary of Meteorology

resonance trough

(Obsolete.) A large-scale pressure trough that forms in a location that is consistent with the position of other dominant troughs and the distance between troughs expected from dynamical considerations.

For example, the mean trough over the Mediterranean in winter is referred to as a resonance trough because of its relationship to the two orographically forced troughs of the east coasts of North America and Asia.