Clear-air turbulence

Clear air turbulence weather (CAT), sometimes colloquially referred to as "air pockets", is the erratic movement of air masses in the absence of any visual cues, such as clouds. Clear-Air Turbulence is caused when bodies of air moving at widely different speeds meet; at high altitudes (7,000-12,000 metres/23,000-39,000 feet) this is frequently encountered around jet streams or sometimes near mountain ranges. Clear-Air Turbulence is impossible to detect either with the naked eye or with conventional radar, meaning that it is difficult to avoid. However, it can be remotely detected with instruments that can measure turbulence with optical techniques, such as scintillometers or Doppler LIDARs.