Turbulence

Question 1

Reporting turbulence x3

Answer 1

Light - no difficulty walking-slight changes 5-10kts

Moderate - positive control still/walking difficult - 15/25kt

Severe - abrupt out of control/walking impossible - 25kt+

Question 2

Thermal Turbulence

Answer 2

Over land in late afternoon
Cumulus clouds

Question 3

Mechanical turbulence

Answer 3

Frictional surface causes disruption in flow

Light winds + smooth surface less turbulent

Question 4

Mountain waves turbulence

Answer 4

Form if there is stability on lee side
Requires strong winds 30 degrees to mountain range
Wind speed 20kt on ridge
Effects up to x3 mountain height
Extends downwind 50-100 miles

Question 5

Mountain waves vertical speed

Answer 5

600ft per min

Question 6

Cap clouds

Answer 6

Formed by air being pushed over mountain

Question 7

Lenticular clouds

Answer 7

Below osscilations could be indication of turbulence

Question 8

Mountain wave management tips

Answer 8

Overly at 90 degree to mountain
Fly as high as possible
Avoid flying on leeward side
Pre flight briefing

Question 9

CAT Turbulence in Jet streams

Answer 9

Worst CAT will be on cold air side of jets core

Second worse just above core

Question 10

How is low level wind shear reported

Answer 10

Pilot reports
Low level wind shear alerting system
ATC/METAR (WS27R for example)

Question 11

Horizontal wind shear

Answer 11

Change in wind speed at same level

Question 12

Vertical wind shear

Answer 12

Change in direction or speed in climb or descent

Question 13

Wind shear causes

Answer 13

Frontal passage
Microburst
Thunderstorms

Question 14

Wind Shear - Friction Layer

Answer 14

Mechanical and thermal turbulence in friction layer
Smooth laminar flow above

Question 15

Wind shear - sea/land breeze

Answer 15

Onshore breeze blowing at different direction to inland winds

Question 16

What level is low level wind shear defined as

Answer 16

1600ft - 500m aal

Question 17

Rotor Zone

Answer 17

Hazard associated with MTW
Lies level with the mountain ride

Most power fuel rotor lies beneath the first wave crest on the lee side of range

Question 18

Conditions needed for mountain waves

Answer 18

High wind speed of 15-20kt
Wind direction must be 30 degrees perpendicular to range
Region of marked stability at mountain top
Less stable air above and below

Question 19

Low level wind shear is up to

Answer 19

1600ft

Question 20

Definition of turbulence

Answer 20

Abrupt change in airflow caused by vortices of different sizes.

Question 21

SEV MTW on SIGMET meaning

Answer 21

Downwards of 600ft or more

Question 22

How often should windshread alert systems be updated

Answer 22

Every minute

Question 23

What factors increase the friction layer

Answer 23

Roughness of the terrain - greater roughness greater the mixing and strength of vertical deflection

Wind speed - higher speed more mixing and deflection

Stability of air - instability more mixing

Time of day - warm afternoons thermal convection more mixing