Rossby waves (planetary waves) are meanders of the jet stream with wavelengths of 4,000–12,000 km. When waves are large and slow, they create blocking patterns that trap heat waves or cold spells for weeks.
Troughs (cyclonic curvature) and ridges (anticyclonic curvature) are the visible manifestations of Rossby waves on synoptic charts. DANAs form when a trough pinches off from the main flow.