What phenomenon are jetstreams in excess of 100 kts likely to cause?

Jetstreams are fast-flowing air currents that occur in the atmosphere, typically in the upper troposphere. When jetstreams exceed 100 knots, they often lead to clear air turbulence (CAT). This type of turbulence arises in clear air rather than within a storm and can be difficult for pilots to detect since it is not associated with visual cues like clouds or precipitation.

The interaction between jetstreams and surrounding air masses can create wind shear, where there is a significant change in wind speed and direction over a short distance. Such conditions are conducive to CAT, which can cause abrupt changes in altitude or flight path for aircraft, making it challenging for pilots to maintain a smooth flight. CAT is particularly associated with strong jetstreams because the rapid movement of air leads to turbulence in adjacent layers, catching pilots off guard.

Understanding this relationship is crucial for flight operations, as it highlights the need for dispatchers and pilots to monitor jetstream activity for safety. Turbulence associated with jetstreams can be significant even in otherwise clear skies, emphasizing the importance of respecting high wind speeds in flight planning and operations.