Airline passengers cruising high above the Great Plains east of the Rocky Mountains regularly see the “Fasten Seat Belts” sign illuminate as the pilot announces that other flights in the region are reporting turbulence. Mountain waves in the wind that flows across mountains often are the source of this turbulence.
The National Weather Service defines a mountain wave as “The wavelike effect, characterized by updrafts and downdrafts, that occurs above and behind a mountain range when rapidly flowing air encounters the mountain range’s steep front.” Even though most mountain wave turbulence is at least a few thousand feet above the ground, some of its effects reach the surface. From time to time, such waves give general aviation pilots and their passengers wild rides.
Jack Williams is an instrument-rated private pilot and author of the National Geographic Pocket Guide to the Weather of North America.
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