Weather Flashcards
What is the standard lapse rate?
2 degree loss per 1000ft altitude gain
What indicates more stable air when comparing lapse rates?
If the lapse rate is less than the standard lapse rate
What indicates unstable air when comparing lapse rates?
If the lapse rate is more than the standard lapse rate
What are the characteristics of unstable air?
- Cumuliform Clouds
- Showery precipitation
- Turbulence
- Good visibility
What are the characteristics of stable air?
- Stratiform Clouds/Fog
- Continuous precipitation
- Smooth air
- Poor visibility
What type of air is more stable and resists vertical movement?
Cool dry air
What type of air is more unstable?
Moist warm air
What is an exception to the instability of moist warm air?
Temperature inversion
Fill in the blank: If the lapse rate is less than 2 degrees per 1000ft, the air is _______.
more stable
Fill in the blank: If the lapse rate is greater than 2 degrees per 1000ft, the air is _______.
unstable
Which is more dense: dry air or humid air?
Dry air is more dense than humid air
What does relative humidity measure?
Relative humidity measures the percent of water vapor held vs. how much is possible
How does temperature affect relative humidity?
Higher temps have lower relative humidity with the same amount of water vapor
How much does the possible water vapor held change with temperature?
Possible water vapor held doubles every 20°F
What is dewpoint?
Dewpoint is the temperature where the air can’t hold any more moisture
What are the three classifications of clouds based on altitude?
Low: Surface to 6500 ft AGL
Middle: 6500 - 20000 ft AGL
High: 20000 ft AGL and above
AGL stands for Above Ground Level.
Which clouds are classified as low altitude clouds?
Stratus, Stratocumulus, Nimbostratus
These clouds are typically found at lower altitudes.
Which clouds are classified as middle altitude clouds?
Altostratus, Altocumulus
These clouds are found between 6500 and 20000 ft AGL.
What are the high altitude clouds?
Cirrostratus, Cirrocumulus, Cirrus
These clouds are generally above 20000 ft AGL.
What is fog?
A cloud on the surface to 50 ft AGL
Fog significantly reduces visibility.
What is radiation fog?
Fog that forms when the ground cools rapidly and air temperature reaches the dew point
This type of fog typically occurs during the night or early morning.
What is advection fog?
Fog that forms when warm air moves over a cold surface, requiring wind
Commonly found in coastal areas.
What is upslope fog?
Fog formed when moist air is forced up land features, requiring wind
This type of fog is often seen in mountainous regions.
What is steam fog?
Fog that occurs when cold air moves over warm water
This type of fog can often be seen over lakes or rivers.
What is ice fog?
Fog formed when water vapor rapidly turns into ice crystals
Typically occurs in extremely cold temperatures.
What is precipitation?
Any water particles falling to the ground
This includes rain, snow, sleet, and hail.
What is virga?
Rain that evaporates before touching the ground
This phenomenon can create a visual effect in the sky.
What are the types of icing?
Instrumental, Induction, Structural (Clear, Mixed, Rime)
Icing can significantly affect aircraft performance.
What is an air mass?
A large body of air with general uniformity, characterized by its location of formation
Air masses can influence weather patterns.
What is a warm front?
Advancing warm air that replaces cold air, rising and slow moving
Associated with increasing temperatures and steady rain.
What weather conditions are associated with a warm front?
Temp increases, poor visibility, steady rain, low stratus clouds
Warm fronts typically move between 10-25 mph.
What is a cold front?
Advancing cold air that replaces warm air, moving at 25-30 mph, up to 60 mph
Cold fronts slide under warmer air, often leading to heavy rain.
What weather conditions are associated with a cold front?
Good visibility, temperature decreases, rising pressure, heavy rain
Cold fronts can lead to severe weather.
What is an occluded front?
A cold front overtaking a warm front, causing severe weather and fog
This type of front can lead to complex weather patterns.
What is a stationary front?
Neither front can overtake the other. Can cause several days of bad weather
Stationary fronts occur when the air masses on either side are not strong enough to displace each other.
What are the stages of a thunderstorm?
- Cumulus: clouds begin to develop vertically
- Mature: most violent, precipitation starts
- Dissipation: clouds spread out, begin to lower
These stages represent the lifecycle of a thunderstorm, from formation to dissipation.
What is the hazard associated with turbulence in thunderstorms?
Severe enough to cause structural damage, severity proportional to air instability
Turbulence can pose risks to aircraft and buildings, especially in unstable air conditions.
What is wind shear?
Sudden drastic changes in wind direction and velocity
Wind shear can create dangerous flying conditions, especially during takeoff and landing.
What is a microburst?
Most dangerous hazard; air drops at high speeds and spreads out
Microbursts can cause rapid changes in wind conditions, leading to potential aircraft accidents.
What are the dangers of lightning in thunderstorms?
Danger of interfering with electrical systems
Lightning strikes can cause power outages and damage to electronic equipment.
What is the risk associated with hail during thunderstorms?
Danger of structural damage
Hail can cause significant damage to roofs, vehicles, and crops.
What does the FAA recommend regarding thunderstorms?
Stay clear of thunderstorms by 20 miles
This recommendation helps to ensure safety from the hazards associated with thunderstorms.
What are squall lines?
Huge lines of thunderstorms
Squall lines can produce severe weather conditions, including heavy rain and strong winds.
What is the purpose of observations like AWOS, METAR, and PIREP?
To report what is happening now
These observations provide real-time data on weather conditions for pilots and meteorologists.
What is the purpose of forecasts in weather reporting?
What is predicted to happen next
Forecasts are essential for planning and safety in aviation and other sectors affected by weather.
What does AWOS stand for?
Automated Weather Observing System
AWOS provides live weather broadcast within 25 miles under 10,000 ft.
What does METAR represent?
Observation of current surface weather
METAR reports are issued hourly and provide essential weather information for pilots.
What does PIREP stand for?
Pilot Reports
PIREPs are real-time weather reports provided by pilots, relayed by radio.
Why is weather forecasting complex?
Weather is too complex to accurately forecast 100% of the time. The farther out the forecast, the less accurate it becomes.
How delayed are NEXRAD mosaics?
NEXRAD mosaics are delayed up to 15 minutes.
What does TAF stand for and what does it forecast?
TAF stands for Terminal Aerodrome Forecast and forecasts weather 5 miles around an airport, typically valid for 24 hours.
Who typically writes TAFs?
TAFs are typically written by a human.
What is MOS in weather forecasting?
MOS stands for Model Output Statistics and can be used to supplement forecasts, written by robots.
At what altitude do winds and temperatures aloft start?
Winds start at 1500ft AGL and temperatures start at 2500ft AGL.
What is an AirMet?
AirMet is a concise report of hazards en route, typically valid for 6 hours.
What does the Sierra AirMet indicate?
Sierra indicates mountain obscuration.
What does the Tango AirMet indicate?
Tango indicates moderate turbulence.
What does the Zulu AirMet indicate?
Zulu indicates moderate icing.
What is a SigMet?
SigMet warns of more severe hazards en route, typically valid for 4 hours.
What are Convective SigMets associated with?
Convective SigMets are associated with convective activity such as severe icing, severe winds, hail, and tornadoes.
How long are Convective SigMets valid?
Convective SigMets are valid for 2 hours.
What are performance limitations in aviation?
Performance limitations refer to what the plane can physically do and what it cannot do.
How does altitude affect aircraft performance?
Lower altitude = better performance because air is more dense.
How does temperature affect air density?
Cold air is denser than warm air.
What does low density altitude indicate?
Low density altitude indicates high air density, which results in better performance.
What is the formula for pressure altitude?
Pressure altitude = 1000 x (29.92 - Current altimeter setting) - field elevation.
