A107 Flashcards
An air mass moving over a warm surface and is heated from below (convective heating) creates what effects?
Unstable air and turbulence
Warm fronts cause what type of precipitation?
Light to moderate precipitation
Warm fronts likely cause what type of clouds?
Blanket-type (stratus) clouds
What type of effect does an air mass passing over a cold surface create?
Creates a stable air mass with poor visibility
At what speed do cold fronts move?
Rapidly
Which front stays close to the ground?
Cold front
What kind of clouds are created from cold fronts?
Towering cumulus and cumulonimbus
What type of weather/precipitation is associated with cold fronts?
Severe weather with extreme precipitation
What three things must be present for clouds?
Adequate water vapor Condensation nuclei (dust particle to cling to) Air to cool to reach its saturation pointx
Define low clouds
Surface to 6500, mostly water droplets (fog included)
Define middle clouds
6500-20000
Composed of water, ice crystals, and supercooled water droplets
Can produce turbulence and moderate icing
Define high clouds
Above 20,000
Composed of ice crystals
Form in stable air
What is a major factor in circulation of air?
Uneven heating of the earth’s surface
where is the troposphere?
From sea level to 20,000-48,000 (poles and equator, respectively)
What is the tropopause?
Top layer of troposphere—there is turbulence here
What is the Coriolis effect?
Causes deflection to right in northern hemisphere and deflection to left in Southern Hemisphere
What happens in unstable air?
Small vertical air movements tend to become larger
Generates turbulence and convective weather
What is temperature inversion?
Air gets warmer as temperature increases (to a certain point)
The layer at the top acts as a lid—traps pollution, haze, smoke—can result in decreased visibility
What happens in stable air?
Makes vertical movement difficult; sometimes associated with temp inversion
What hazards to aviation may be present from thunderstorms?
Updrafts/downdrafts, large hail stones, lightning, tornadoes, windshear, severe turbulence
Define windshear
A sudden, drastic change in wind speed or direction
What commonly causes windshear?
Passing frontal systems, thunderstorms,
temperature inversion, and surface obstruction
Define microburst
A critical type of shear
Typically has diameter of 1-2 miles
Usually 15 min lifespan
Downdrafts up to 6,000ft/min
What is a METAR
Hourly observed weather report
When is a METAR observed?
45min to top of the hour
When is a METAR reported?
50 min to top of the hour
How far from an airfield does a METAR include weather info for?
5 miles
If a METAR says “VC” what does this mean?
In the vicinity—5-10 miles
What does DSNT mean on a METAR?
Distant—greater than 10 mikes
What are the five levels of cloud coverage?
Skc—sky clear Few—1-2/8 Sct—3-4/8 Bkn—5-7/8 Ovc—8/8
What is a TAF?
A weather forecast
What type of weather can be expected from moist, unstable air and very warm surface temperature?
Strong updrafts and cumulus clouds
What are the three stages of a thunderstorm?
- cumulus stage: lifting action begins, needs moisture and instability
- Mature stage: most violent time, precipitation begins to fall
- Disappearing stage: downdrafts spread out, lifting action stop
What happens if a wind shear causes a headwind to change to a tailwind?
Loss of aircraft performance
What is prevailing visability?
The greatest horizontal visibility observed through at least half the horizon circle and is not not necessarily continuous
How long is a routine TAF valid?
24 hours
