MOUNTAIN WAVES

Question 1

Mountain waves, winds and Turbulence:

Answer 1

Oscillations on the Lee side (down wind) side of a mountain caused by the disturbances in the horizontal air flow due to terrain that is in the way.

Question 2

How does the most common mountain wave form?

Answer 2

As winds are forced up an impeding mountain range, and than defends down the other side.

Question 3

Where are down drafts the most severe?

Answer 3

Near the mountain or mountain ridges and about the same height as the summit

Question 4

How fast can a down draft reach?

Answer 4

83 FPS, or 5000 FPM

Question 5

What angle must wind direction be?

Answer 5

Within 30 degrees perpendicular to the mountain, and must be 25 kt or more on the windward side

Question 6

What two parts are the mountain waves composed of?

Answer 6

Amplitude
Wavelength

Question 7

What factors can change wave length?

Answer 7

Stability
Wind speed
Lateral positioning of ridges
Ridge spacing

Question 8

Amplitude is what?

Answer 8

Half the vertical distance from the wave trough to the crest.

Question 9

What is generally true regarding amplitudes and wavelengths?

Answer 9

The greater the amplitude=the shorter the wave length

Question 10

What can change the Amplitude of a wave?

Answer 10

Stability
Mountain size
Mountain shape
Sharp Lee side
(Drops in 3000 ft cause the largest amplitudes)

Question 11

Orographic clouds caused by?

Answer 11

Air is forced to rise by the earth’s topography

Question 12

What is required for clouds to form?

Answer 12

Sufficient moisture

Question 13

What can give us an indication that mountain waves/turbulence exist?

Answer 13

Lenticular clouds
Rotor clouds
Cap clouds
Banner clouds

Question 14

Lenticular clouds

Answer 14

Typically 20-40,000ft
Form in the crests of the waves

Question 15

How do METARS/ PIREPS Report Lenticular clouds?

Answer 15

ACSL - Alto Cumulus Standing Lenticular
CCSL- Cirro Cumulus - Standing Lenticular

Question 16

Roll/Rotor Clouds:

Answer 16

Another indicator of mountain wave presence. They process the greatest amounts of turbulence

Question 17

Where will Roll/rotor clouds form?

Answer 17

These will form down wind from each wave crest and within the lower turbulent zone.

Question 18

Where is the Roll/rotor clouds center of rotation?

Answer 18

Typically near the ridgeline.

Question 19

Rotor clouds intensity?

Answer 19

2000-5000 FPM
Produce severe turbulence
The first rotor is typically the most intense although ALL of them spell trouble

Question 20

What may result with a mountain wave and a nonstandard temperature regarding the altimeter reading?

Answer 20

It may over read by as much as 3000 ft

Question 21

Anabatic winds

Answer 21

Sun side of a mountain slope heats up
Warm air rises creating an upwind flow
Pockets of turbulence can occur as different parts of mountain heat up at different rates

Question 22

Katabatic winds

Answer 22

A wind that flows down the slope of mountain. More powerful At nights when radiation cooling starts to happen at night. Blowing down glaciers = extreme katabatic

Question 23

Funnel winds = decreased pressure =

Answer 23

Error in altimeter reading

Question 24

Next to thunderstorms, what is the worst meteorological hazard we pilots face?

Answer 24

Mountain turbulence, in particular Rotor turbulence

Question 25

If caught in down draft what should you do?

Answer 25

Speed up to get out of it sooner