A weather disturbance is a pulse of energy moving through the atmosphere, typically mid or upper atmospheric troughs of low pressure embedded in general wind flows. Key weather disturbances include tropical cyclones, which are intense circular storms over warm oceans with low pressure, high winds and heavy rain; tornadoes, which are small violently rotating columns of air from convective clouds touching the ground; cyclones, which are large low pressure systems with circulating winds and rain or snow; and storms, which are violent disturbances with low pressure, clouds, strong winds, and precipitation that often form from low pressure areas.