Turbulence is air movement that normally cannot be seen. It may occur when the sky appears to be clear and can happen unexpectedly. It can be created by any number of different conditions, including atmospheric pressures, jet streams, mountain waves, cold or warm fronts, or thunderstorms. Light chop - slight, rapid and somewhat rhythmic bumpiness without noticeable changes in altitude or attitude. Moderate turbulence - similar to light turbulence, but greater intensity.
Aircraft remains in control at all times.
Variations in indicated air speed. Moderate chop - similar to light chop, but greater intensity. Rapid bumps or jolts without obvious changes in altitude or attitude. Large variation in indicated airspeed. Aircraft may be temporarily out of control.