1. 5.06 Turbulence, Visibility, and Fronts
Meteorology
5.06 Turbulence, Visibility, and Fronts
References:
Air Command Weather Manual Chapters 7, 8, 10 and 11
FTGU pages 133, 138, , 147, 155 and 156
Aviation Weather Student Guide

2. 5.06 Turbulence, Visibility, and Fronts
MTPs:
Types of Turbulence
Wind Shear
Visibility Obstructions
Definition of a Front
Front Formation
Warm Front
Cold Front
Fronts on Maps

3. Isolated convection currents cause turbulence
Types of Turbulence
Convection Turbulence
Thermal Turbulence
Hot sunny days - sun heats the earth’s surface unevenly
Isolated convection currents cause turbulence

4. Types of Turbulence 2. Mechanical Turbulence Also known as “eddies”
Friction between air and ground
Irregular terrain and man-made obstacles cause severe eddies.

5. Types of Turbulence 3. Orographic turbulence Known as mountain wave
Can be expected on the windward side and over the crests of mountains, along the downward slope
Avoid rotor cloud and strong downdraft on the leeward side of mountain

6. Wind Shear
4. Wind Shear
Any marked change in wind speed and direction with height that produces local areas of turbulence
When changes are large, quite
severe turbulence can be expected
Low level wind shear occurs as a
result of gust fronts and downbursts
Associated with thunderstorms

7. Wind Shear
Inversions
Overnight cooling creates temperature inversion a few hundred feet above ground that can produce significant wind shear
Can also form where cold air trapped in low lying areas (ex. valleys) as cold air denser than warm air
At night this air will “flow” into low lying areas

8. Confirmation
1. Wind shear is a sudden change in the wind’s ____________ and/or ___________.
2. ________________ is the condition when the temperature increases with altitude.
3. _____________ causes turbulence due to uneven heating of the ground.

9. Visibility Obstructions
Haze
Very small water droplets, dust or salt particles
Cannot be felt or individually seen with naked eye
Uniform veil, restricts visibility
Only a problem in stable air.

10. Visibility Obstructions
Smoke
Created by industrial pollutants, vehicle exhaust in urban/industrial areas – thick blanket of haze severely restricting visibility
Worse when flying towards the sun
Forest fires can also contribute in more rural areas.

11. Visibility Obstructions
Smog
Combination of smoke and fog
Has a yellow colour to it due the pollution mixed in with it
Often occurs with an inversion
Type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes
Fumes react in the atmosphere with sunlight to form secondary pollutants

12. Confirmation
1. What are some of the visibility obstructions a pilot can face?
2. How is thermal turbulence created?
3. How is an inversion formed?
4. Which part of a mountain would see the worst turbulence?

13. Definition of a Front Definition:
FTGU: Transition zone between two air masses
What’s happening at a front?
Large change of temperature within a relatively short distance of miles in the zone between air masses
The interaction zone between the air masses is responsible for weather changes
Front

14. Front Formation Requirements:
a cold air mass and a warm air mass lying adjacent
mixing action

15. Front Formation Air Mass: May be several thousand miles across
A large section of the troposphere with uniform properties of temperature and moisture
May be several thousand miles across
Cold Air Masses
Warm Air Mass
Instability
Stability
Turbulence
Smooth air
Good visibility
Poor visibility
Cumuliform clouds
Stratiform Clouds and Fog
Shower type precipitation
Drizzle type Precipitation
Hail, Thunderstorms may occur

16. Warm Front A warm front is the retreating edge of a cold air mass
Warm air advances and overruns retreating cold air
Warm air rises since it is less dense than cold air
Usually moves slower than a cold front
Long gentle frontal slope.
Simulation

17. Warm Front Warm front weather
Warm air mass pushes moisture up the slope, causing cloud and precipitation
Overrunning, moisture content and stability of warm air determines severity of weather
If the warm air is unstable, thunderstorms may be embedded

18. Warm Front Ceiling Visibility Precipitation Turbulence
Low ceiling can persist for long periods of time
Visibility
Restricted
Precipitation
Begins in altostratus layer
Becomes heavier as front approaches
Very heavy showers indicate potential thunderstorms
Turbulence
Less severe than cold front (unless cumulonimbus clouds embedded)
Clouds
Cirrus, Cirrostratus, Altostratus, Nimbostratus, Stratus

19. Warm Front Indication of Approaching Warm Front: CCANS Cirrus
Cirrostratus
Altostratus
Nimbostratus
Stratus

20. Cold Front
A cold front is the leading edge of an advancing cold air mass
Cold air undercuts the warm air
Rising warm air expands and cools
Cumulus cloud

21. Cold Front Slope can be very steep
Weather severity determined by moisture content and stability of the warm air mass
Simulation

22. Cold Front Ceiling Visibility Precipitation
Low, with clouds of vertical development, icing and turbulence
Visibility
Good, Usually improves after the passage of the front
Precipitation
Usually a narrow band
Turbulence
Flight through a cold front can be expected to be rough
Clouds
Cumulus, Cumulonimbus, Towering cumulus

23. Cold Front Temperature Pressure May drop sharply after front passes
Usually drops gradually as air behind is warmed by the ground
Pressure
Decrease, followed by a marked rise after frontal passage

24. Warm and Cold Front

25. Fronts on Maps
Red = Warm
Blue = Cold

26. Confirmation
1. Label where the cold front and where the warm front is.
2. Label what clouds are associated with the fronts
3. Draw an arrow to show which direction the front is moving

27. Confirmation What weather is associated with a cold front?
What weather is associated with a warm front?

28. Severe Frontal Weather