FAA Aircraft Dispatcher (ADX)MeteorologyMedium
A dispatcher reviewing satellite imagery near a mountain range identifies smooth, stationary, lens-shaped clouds downwind of the peaks despite strong winds aloft. What condition do these clouds most likely indicate?
- AMountain wave activity with possible severe turbulence in the wave pattern
- BFrontal passage with associated wind shift
- CAn advancing squall line ahead of a cold front
- DDevelopment of a nocturnal radiation inversion
Show answer & explanationAnswer & explanation
Correct answer: A. Mountain wave activity with possible severe turbulence in the wave pattern
Standing lenticular altocumulus (ACSL) clouds form in the crests of mountain waves and remain stationary relative to the terrain even as strong winds flow through them. Their presence is a visual indicator of mountain wave activity, which can produce severe to extreme turbulence, particularly in the rotor zone beneath the wave crest.
Why the other options are wrong
- B. Frontal passage is not indicated by stationary lenticular clouds.
- C. Squall lines are convective and linear, not smooth stationary lens shapes.
- D. Radiation inversions form under clear, calm conditions, not strong wind flow.
Standing Lenticular Clouds (ACSL)
Smooth, lens-shaped clouds that form at the crest of mountain waves and remain stationary despite strong winds passing through them, indicating mountain wave turbulence.
- Form on the leeward side of mountain ranges
- Remain stationary while air flows through them
- Indicate potential severe turbulence, especially in rotor clouds below
Memory trick: Lens-shaped cloud sits still like a UFO parked over the peak.