What wind speed range is typically necessary to support mountain wave formation?

What wind speed range is typically necessary to support mountain wave formation?

• A. 5-15 knots
• B. 15-25 knots
• C. 25-40 knots
• D. 40-60 knots

Answer: (B)

Mountain waves occur when stable air flows across a mountain with a perpendicular wind component, and the wind supplies the energy to push the air up and down behind the peak. If the wind is too light, the disturbance isn’t strong enough to generate a clear, sustained wave pattern. If the wind is too strong, the waves can become steep and turbulent, with rotors and possible wave breaking. The range where waves tend to form as orderly, persistent lee waves is about 15 to 25 knots. This provides enough energy to create the downstream oscillations and often visible lenticular clouds, without immediately triggering excessive turbulence or breaking waves. Wind speeds significantly above this range tend to produce harsher turbulence and rotor activity, while speeds well below it yield weak or absent mountain waves.

Mountain waves occur when stable air flows across a mountain with a perpendicular wind component, and the wind supplies the energy to push the air up and down behind the peak. If the wind is too light, the disturbance isn’t strong enough to generate a clear, sustained wave pattern. If the wind is too strong, the waves can become steep and turbulent, with rotors and possible wave breaking. The range where waves tend to form as orderly, persistent lee waves is about 15 to 25 knots. This provides enough energy to create the downstream oscillations and often visible lenticular clouds, without immediately triggering excessive turbulence or breaking waves. Wind speeds significantly above this range tend to produce harsher turbulence and rotor activity, while speeds well below it yield weak or absent mountain waves.