Wind Shear and Turbulence Flashcards
What is Wind Shear?
Change in speed and/or direction over a short distance.
Where can wind shear occur?
High and low altitude, either vertically or horizontally.
What is wind shear most often associated with?
Strong temperature inversion or density gradients.
True or False?
Wind shear may be associated with TS, low-level temperature inversion, a jet stream or a frontal zone.
True
What are some examples of Wind Shear situations?
Mountains and hills, funnel winds, anabatic winds, katabatic winds, land/ sea breezes, low level nocturnal jet, TS and frontal shear.
Can significant wind shear occur when flying from one air mass to another?
Yes
Wind shear is most likely where in a warm and cold front?
Within 100 nm ahead of warm fronts (in cold air)
Within 50 nm behind cold fronts
When is wind shear a problem at cold fronts?
When there is a steep wind gradient
What are signs wind shear may occur at a cold front?
T difference across front at the surface in more than 5C
Front is moving at least 30kts
When is wind shear likely at a warm front?
When flow ahead is strong and parallel to the front.
What speeds can the funnel winds reach out of mountain valleys?
80 kts
Explain the Chinook wind process.
Deep layer of moist air from Pacific is forced upwards along a mountain.
Rises, cools and becomes saturated.
Precipitation that falls out is lost to the air mass, so it becomes drier.
Upon descending on the leeward slope it is heated at the dry adiabatic lapse rate.
Arrives at lower elevation warmer and drier than before.
What are the conditions for mountain waves to form?
Wind direction within 30Deg of the perpendicular.
Winds at crest in excess of 15 kts
Less stable air above the ridge
Mountain waves are associated with?
Severe turbulence, strong vertical currents and icing.
What is the speed and distance inland of a land breeze?
10-15 kts and may reach 50 miles inland.
Which is stronger, a land or sea breeze?
Sea breeze
What is a low-level nocturnal jet?
A sheet of strong winds thousands of miles long, hundreds of miles wiles wide and hundreds of feet thick.
What is the level maximum of a low level nocturnal jet?
700 - 2000 ft above ground
What are the wind speeds in a low level nocturnal jet?
25 - 45 kts at maximum.
Turbulence is caused by which air motions?
A random spin motion of the air caused by strong wind shear
Abrupt up and down drafts.
What are the types of turbulence?
Convective, mechanical, shear, wake, lee wave and thunderstorm.
What is convective turbulence?
When an aircraft passes through a rising convective cell.
Explain the path and motion of wing tip vortices.
Vortices extend 500 - 1000ft below an AC
They sink at 4- 500 ft per minute
Spread out laterally at about 5 kts.
How do you avoid wake turbulence?
Stay 2-3 mins behind heavy aircraft
Stay above AC’s approach
Touch down beyond heavy Ac’s touch down point
