What does clear air turbulence mean?
Turbulence is not only encountered in cloud-bands and stormy weather; it occasionally occurs in perfectly clear air. Clear Air Turbulence (CAT) builds up at altitudes of ten to fifteen km at the edge of ‘jetstreams\ One can find these long narrow air-streams gusting at 100 to 500 km per hour over the Atlantic. CAT is often unpredictable, it occurs without warning and generally lasts only a few seconds or minutes. The jolts can be quite violent, however. So to prevent injury it is advisable to keep your seat-belt fastened even when cruising, and especially if you intend to take a nap.
