Mountain waves and rotors
How waves form, the clouds that betray them, and staying out of the rotor.
14 min read · Mountain and high-altitude flying
After this lesson you can
- Explain why a ridge produces smooth lift on its windward side and severe turbulence on its leeward side.
- Recognize lenticular clouds as the visible signature of a mountain wave.
- Explain why the same turbulence can exist with no cloud at all to mark it.
- Decide when to turn back rather than try to out-climb a downdraft on the lee side of a ridge.
A mountain wave can produce some of the most violent turbulence a light airplane will ever encounter, under a perfectly clear sky, with no radar echo and no PIREP to warn about it. It forms wherever wind is forced over a ridge and then has to come back down the other side, and it is entirely predictable from the wind and the terrain, hours before the airplane ever gets there.
This lesson works from the mechanism outward: what makes the windward and leeward sides of a ridge behave so differently, what a lenticular cloud is actually telling a pilot, why dry air can hide the same hazard with no cloud at all, and what to do when a descent on the far side of a ridge starts winning against the airplane's climb.
The rest of this lesson
- 1.Windward smooth, leeward rough
- 2.A standing wave downwind of the ridge
- 3.Lenticular clouds: the visible signature
- 4.No cloud does not mean no wave
- 5.Getting a mountain checkout
- 6.When the descent wins: the 180-degree option
These 6 sections, their figures, the checks along the way and the end-of-lesson quiz come with the CPL track. Paid once, yours for good.
Key terms
Try to recall each definition before turning the card.