Mountain waves are formed when strong winds (40 knots or greater) flow across a barrier, such as a mountain ridge. When the air is stable, the flow is laminar, or layered, and create a series of waves. Unstable air that is forced upward tends to continue
parallel to a mountain peak, and the air is stable.
down a mountain valley, and the air is unstable.
across a mountain ridge, and the air is stable.
Wind shear can occur at middle and high altitudes near thunderstorms or the jet stream, and near the ground in the vicinity of thunderstorms or temperature inversions. The shear can be either vertical or horizontal.
Only at lower altitudes.
Only at higher altitudes
At all altitudes, in all directions.
Wind shear can be found above a temperature inversion when the surface air is cold and calm, and the warmer layer above it is moving at 25 knots or more. Since frontal zones are identified by a shift in the wind, wind shear can be expected. Clear air turb
In areas of low-level temperature inversion, frontal zones, and clear air turbulence.
Following frontal passage when stratocumulus clouds form indicating mechanical mixing.
When stable air crosses a mountain barrier where it tends to flow in layers forming lenticular clouds.
A temperature inversion with light surface winds may form near the surface on a clear night. You can expect a shear zone in the inversion if the winds at 2,000 to 4,000 feet are 25 knots or more.
Structural icing requires two conditions to form: (1) visible moisture, such as rain or cloud droplets, and (2) temperature of the aircraft surface must be at or below freezing. A small temperature/dewpoint spread may be present without visible moisture.
small temperature/dewpoint spread
The rate of structural ice accumulation is usually the highest in freezing rain below a frontal surface. As the rain falls through air with temperatures below freezing it becomes supercooled. The supercooled drops freeze on impact with the large water dro
Cumulus clouds with below freezing temperatures
Frost disrupts the smooth airflow over the wing and can cause early separation of the airflow, resulting in a loss of lift.
Frost changes the basic aerodynamic shape of the airfoils, thereby decreasing lift.
Frost spoils the smooth flow of air over the wings, thereby decreasing lifting capability.
Frost slows the airflow over the airfoils, thereby increasing control effectiveness.
Frost disrupts the smooth airflow over the wing and can cause early separation of the airflow, resulting in a loss of lift. By disrupting the airflow over the wings, frost can prevent an airplane from becoming airborne at the normal takeoff speed.
Frost may cause the airplane to become airborne with a lower angle of attack at a lower indicated air speed.
Frost will change the camber of the wing, increasing lift during takeoff
Frost may prevent the airplane from becoming airborne at normal takeoff speed
Three conditions are normally required for the formation of cumulonimbus clouds. These are lifting action, instability and moisture.
unstable, moist air
either stable or unstable air
unstable air containing an excess of condensation nuclei
In the early, or cumulus, stage of a thunderstorm, continuous updrafts cause the cloud to build upwards.
The mature stage of a thunderstorm begins when the rain drops grow too large to be supported by the updrafts, and precipitation begins to fall.
The appearance of an anviI top
Maximum growth rate of the clouds
Precipitation beginning to fall
The outflow from a mature thunderstorm west of the airport cloud create significant winds from the west. If landing on Runway 08, the aircraft could experience a dangerous sheer to a tailwind. Landing to the west, on Runway 26, is the best choice. In addi
fly the normal pattern to runway 08 since the storm is west and moving north and any unexpected wind will be from the east or southeast toward the storm.
fly an approach lo runway 26 since any unexpected wind due to the storm will be westerly.
fly the pattern to runway 08 since the storm is too far away to affect the wind at the airport
Three conditions are normally required for the formation of cumulonimbus clouds. These are lifting action, instability and moisture. As moist, unstable air is lifted, it builds cumulonimbus clouds, which form thunderstorms.
High humidity, high-temperature, and cumulus clouds.
High humidity, lifting force, and unstable conditions.
Lifting force, moist air and extensive cloud cover.
As moist, unstable air is lifted, it builds cumulonimbus clouds, which form thunderstorms. The mature stage of a thunderstorm begins when the rain drops grow too large to be supported by the updrafts, and precipitation begins to fall. As a thunderstorm di
Thunderstorm are most violent during the mature stage, with strong updrafts and downdrafts, severe turbulence, lightning, heavy rain, hail, strong surface winds, and gust fronts.
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