Aviation Weather Flashcards
What causes every physical process of weather?
Heat exchanges
What causes differences in pressure and altimeter settings?
Uneven heating of the Earths surface
What causes the developments of thermals?
Solar heating
What is a front?
Zone of transitionary between two air masses of different density’s
- e.x. High pressure and low pressure5
What kind of air does high pressure consist of?
Area of descending air
What kind of air does low pressure area have?
An area of rising air
What is the most recognizable change when crossing a front?
The change in temperature and always a change in wind
What are the three phases of a Thunderstorm?
Cumulus
Mature
Dissipating
What happens during a cumulus stage of a thunderstorm?
The building stage consists of continuous updrafts
What happens during the mature stage not a thunderstorm?
Greatest intensity of the thunderstorm, start of precipitation, both updrafts & downdrafts, wing shear, turbulence
What happens during the Dissipating stage of a Thunderstorm?
Only downdrafts, storm is raining itself out
How is a thunderstorm produced?
By cumulonimbus clouds
- sufficient water vapor
- an unstable lapse rate
- an initial upward boost to start the process
Can you fly under the anvil of a thunderstorm?
No, there is still potential for severe clear air turbulence, hail
What are the most severe thunderstorm conditions and what are they generally associated with?
The most severe conditions are heavy hair, destructive winds, and tornadoes. They are associated with squall line thunderstorms
What is automatically expected with thunderstorms
Lightning bc causes thunder
What is a squall line
Non frontal narrow band of thunderstorms
What two conditions are need for structural icing?
Visible moisture and temperature at freezing or below
What causes the greatest accumulation of structural ice
Freezing rain
How does frost form?
Wen temperature of the collecting surface is at or below the dew point of the adjacent air and the dew point is below freezing
What happens when there is front on the wings?
Decreases lift, causes friction, and increases drag, may make it impossible to t/o
What are lenticular clouds
Almond or lens shaped clouds, may contain winds of 50kts or more, appear stationary, most commonly found on the leeward side of a mountain range
When can you expect mountain wave turbulence
Air is stable, and winds of 40kts or more blow across a mountain or ridge
What is a rotor cloud
A rotary circulation under each wave crest, the turbulence is most frequent and severe below these clouds
When can wind shear occur
Any altitude and can be vertical or horizontal. Most likely with a temp inversion that’s 25kts or Moore while between 2000-4000AGL. Also, any low temp inversions, frontal zones, clear air turbulence
What happens when the temp and dew point are within 5 degrees Fahrenheit of each other or less
Expect fog, low clouds
What is dew point
Temperature at which the air will have 100 humidity/saturated
What determines how much water vapor can be held by the air
Air temperature
What is evaporation
Liquid to water vapor
What is sublimation
Solid to gaseous state
What is deposition
Gaseous state to solid
What are the types of fogs
Radiation fog
Advection fog
Upslope fog
Precipitation-induced fog
Freezing fog/ice fog
Steam fog
What is radiation fog
“Morning fog”, clear skies, calm winds, long nights, small temp/dew spread
- forms at night when surface cools, causing air above to cool, till early morning and dissipates after sunrise
Prone in valleys and lay lying areas
What is advection fog
Warm moist air moves over cooler ground/water
Forms with strong wind and clouds, shallow and associated with inversions
Prone in coastal areas
What is upslope fog
Moist air flows upward over rising terrain, causing it to cool to dew point
Prone at higher elevations, and build into valleys, high winds, windward side of terrain
What is steam fog
Evaporation fog, cold/dry air in contact with warm water, warm water evaporates increasing moisture
Prone over bodies of water, early fall or late spring
Susceptible to low level turbulence and icing
What is freezing fog/ice fog
Saturated air when surface temp is below freezing point
Freezing: droplets cannot freeze in air bc lack of nucleus, form at or just below freezing / cold winters, valleys, cold air pools, freeze on impact with surface
Ice: ice crystals, below freezing, 0
What is precipitation fog
Warm air/drizzle falls through cooler ground air and evaporate and saturates the cool air causing fog
Prone with fronts, proximity of icing, turbulence, thunderstorms
How are clouds classified and what are their types
Height
High clouds, middle clouds, low clouds, and clouds with extensive vertical development
What cloud has the greatest turbulence
Cumulonimbus clouds
Formed by lifting action, unstable air, moisture
What cloud indicate convective turbulence
Towering cumulus
What does nimbus mean
Rain
What is the temp and dew point converting point
4.4 Fahrenheit / 1000 ft
How do you find the base of a cumulus cloud
Find the difference between the dew and temp, then divide it by 4.4.
What are unstable characteristic s
Cumuliform clouds, turbulent air, good visibility, showery precipitation, warm, humid
What are stable characteristics
Stratiform clouds, smooth air, fair/poor visibility, continuous precipitation, cool ,dry
What is a temporal inversion
When air temp increases as altitude increases, stable air, often near ground on clear, calm, cool nights (caused by terrestrial radiation)
- smooth air with limited visibility
What are cirriform clouds
20000 ft above, composed of ice crystals, thin/white, occur if fair weather and point in direction of air movement
What are nimbus clouds
Rain, 7000-12000 ft, bases lower towards the ground when thickened and precipitations falls
What are cumuliform clouds
White/fluffy, vertical/uplift formation created by humidity of rising air, more humid means lower the base, can reach 60000ft
What are stratiform clouds
“Blanket”, featureless low layer, gray/dull weather, only a few hundred feet AGL
(Moist, stable air moving up a mountain)
(Steady precipations preceding a front)(
What causes instability
When air is warmed below
What determines the stability of air masses
Actual lapse rate
