Wind Flashcards
How is wind direction described?
The direction the wind is blowing from in degrees clockwise from North
How is wind strength measured?
Knots (kts)
How is wind velocity measured?
Using a combination of direction, strength and gusts I.e.
23020G35kts
Wind blowing 230 degrees from true north
20kts of wind
Gusts of up to 35kts
What does 23020G35kts mean?
Wind blowing from 230 degrees from true north
Wind at 20kts
Gusts of up to 35kts
How will ATS or ATC describe wind?
In degrees magnetic as that is how runways are measured
What is it called if wind is changing direction clockwise?
Veering
What is veering wind?
Wind that changes direction clockwise
What is wind that changes direction anti-clockwise called?
Backing wind
What is backing wind?
Wind that changes direction anti-clockwise
If there is an area of high pressure on the equator and low pressure directly north what will happen to the wind?
It will overshoot and blow past the low pressure point due to Coriolis force (earths rotation)
If there is an area of high pressure in the northern hemisphere and low pressure directly north on the equator, what direction will the wind blow?
Towards the low pressure but it will undershoot due to the earths rotation and coriolis force
If wind is faster what happens to the coriolis force?
It increases, so depending on the location of the pressures it will undershoot or overshoot more drastically
What direction will wind flow relative to the isobars?
Parallel to the isobars
Buys Ballot law tells us that if we stand with the wind on our back in the Northern Hemisphere…
The area of low pressure will be on our left
If you are experiencing right (starboard) drift this means…
Wind is coming from the left and you are flying into low pressure (usually has worse weather)
If you are experiencing port (left) drift in the Northern hemisphere then…
You are flying into high pressure as the wind blowing from your right (usually has better weather)
Wind that is pulled around low pressure in the northern hemisphere moves in what direction?
Anti-clockwise aka cyclone
Wind that is pulled around a high pressure in the northern hemisphere moves in what direction?
Clockwise aka anticyclone
What is a cyclone in the northern hemisphere?
Wind that is moving anti clockwise around low pressure
What is an anticyclone in the northern hemisphere?
A wind moving clockwise around an area of high pressure
Where is surface wind measured?
30ft above open and level ground
Surface wind is weakest at what areas of land?
Rough areas I.e. crowded cities and vegetation filled mountains
Surface wind is strongest at what locations?
Smooth areas like oceans and flat deserts
At what heigh do frictional affects not impact wind?
Around 2000-3000 ft above ground level
What are the 4 turbulence intensities?
Light
Moderate
Severe
Extreme
What is light turbulence?
Represented with /\
And means there is a slight change in altitude or attitude
What is moderate turbulence?
Represented with _/_
There is a change in altitude or attitude and the indicated airspeed.
Requires pilot intervention to keep flight safe
What is severe turbulence?
Represented with //\
The aircraft is momentarily out of control and there are large abrupt changes in attitude and airspeed
What is extreme turbulence?
Represented with _///\_
Aircraft is tossed violently out of control and it is virtually impossible to control.
Airspeed exceeds limitations and structural damage is likely
Are surface winds stronger during the day or night?
Day due to mixing layers
When is wind shear stronger?
Night
What is wind shear?
Rapid change in wind velocity or direction
What causes a sea breeze?
On a hot day the land heats up and air above it rises. Sea air rushes in to replace this air.
What weather is caused by a sea breeze?
Coastal weather becomes foggy and misty with reduced visibility (often affects coastal aerodromes)
What is a land breeze?
Land cools quicker at night causing air to sink. This forces air on the coast back out to sea.
What is katabatic wind and when does it usually occur??
When air on an elevated location I.e. a mountain cools and runs down the side. Often happens at night due to land cooling
What is anabatic wind and when does it occur?
Air heats during the day and flows up the side of the elevated location I.e. a mountain. The winds are usually weaker as they fight against gravity
Which has stronger winds: anabatic or katabatic winds?
Katabatic as it is aided by gravity
Where does wind shear often occur?
During take off and landing as altitude changes, near thunderstorms, temperature inversions and coastal areas where there is a sea or land breeze.
Why should you avoid flying near mountains during strong winds?
Wind blows onto the mountain face causing turbulence on the Lee side of the mountain
How far away should you stay from mountains during strong winds?
2000-3000 feet
Where do lenticular clouds form?
Lee side of the mountain. They look like waves and inform us of high turbulence
Why is turbulence dangerous?
It will over-stress the plane causing the plane to stall at higher speeds
How can you avoid turbulence?
Stay 10-20nm from cumulonimbus clouds
Don’t fly on the Lee side of hills in strong winds
These turbulent winds can occur up to 100nm from the Lee side of the mountain
What is the difference between surface winds and regular winds in stable conditions inland
Backs 40-50 degrees
Ground winds are 25%
What is the difference between surface winds and regular winds in partially unstable conditions inland
Backs 30 degrees
Surface winds are 35%
What is the difference between surface winds and regular winds in unstable conditions inland
Backs 10-20 degrees
Surface winds are 50%
What is the difference between surface winds and regular winds in stable conditions at sea
Backs 15-20 degrees
Surface winds at 80%
What is the difference between surface winds and regular winds in unstable conditions at sea
Backs 5-10 degrees
Surface winds at 90%
What is a col.
Area of stagnant air between two highs and two lows
What are Foehn conditions?
Stable air blows against a mountain causing moderate to severe turbulence
What is a rotor?
When air on the Lee side of a mountain blows in a circular motion causing turbulence
How much does friction affect airspeed?
Wind speed increases by 15kts per 1000 ft
What is convergence and what does it cause?
Air comes together and rises causing cloud formation
Does wind back more in land or at sea?
In land
Does wind back more in stable or unstable conditions?
Stable backs more
Is there a higher percentage of surface wind at land or sea?
Higher percentage at sea
Is there a higher percentage of surface wind in stable or unstable conditions?
Unstable has a higher percentage of surface wind
Meteorological reports on wind direction are relative to ________________
True north
Reports of wind at an airfield passed to a pilot from ATCare relative to____________
Magnetic north at the airfield
280/34kt on a meteorological forecast or observation means
Wind strength of 34 knots blowing from 280 degrees true north
What happens to wind during the day?
Stronger winds
Veer and increase
What happens to wind during the night?
Weaker
Back and slack
What is windsheer?
Change of wind from place to place
What does this mean?
MTW MAX VSP 500 FPM070
Mountain waves, max vertical speed 500 feet per minute
What separation should you keep from mountain?
2000 - 3000 ft
