Fundamentals Of WX Flashcards
At what rate does atmospheric pressure decrease with altitude?
Atmospheric pressure decreases approximately 1” Hg per 1,000 feet.
What are the standard temperature and pressure values at sea level?
15°C and 29.92” Hg.
How does air flow around low-pressure systems in the northern hemisphere?
Inward, upward, and counterclockwise.
How does air flow around high-pressure systems in the northern hemisphere?
Outward, downward, and clockwise.
What general weather is associated with low-pressure systems?
Cloudiness, precipitation, and bad weather due to rising air.
What general weather is associated with high-pressure systems?
Clear skies and good weather due to descending air.
**What weather conditions are commonly encountered near a cold front?
**
- T.
- H.
- P.
- G.
You can remember it as “The Happy Penguins Glide” to make it a bit more fun!
* Towering cumulus or cumulonimbus clouds
* Heavy rain
* Poor visibility
* Gusting winds**
What weather conditions are commonly encountered near a warm front?
You can remember it as “Silly Ducks Love Playing Violins” to make it a bit more fun!
S
D
L
P
V
Stratiform clouds
Drizzle
Low ceilings
Poor visibility
Variable winds
What is a cold front?
A cold, dense air mass advancing and replacing a warmer air mass.
What is an occluded front?
A fast-moving cold front catching up with a slow-moving warm front.
What is a warm front?
A warm air mass contacts and flows over a colder air mass.
What is a stationary front?
A boundary between two air masses that remains stationary, often resulting in mixed weather.
What is a trough in meteorology?
An elongated area of low pressure associated with rising air, cloudiness, and precipitation.
What is a ridge in meteorology?
An elongated area of high pressure associated with descending air and good weather.
What is a dryline and why is it important?
A dryline is a boundary separating moist and dry air masses. Severe thunderstorms often develop along or near it.
Why do surface winds flow across isobars at an angle?
Surface friction causes winds to flow across isobars at an angle.
When temperature and dew point are close together, what weather is likely?
Visible moisture such as clouds, dew, or fog.
What factor primarily determines the type and vertical extent of clouds?
The stability of the atmosphere.
How does atmospheric stability affect vertical air movement?
A stable atmosphere resists vertical movement, while an unstable atmosphere promotes it, leading to turbulence.
How do you determine atmospheric stability?
By observing temperature lapse rates; steeper lapse rates indicate less stability.
What are the effects of stable air on clouds, turbulence, precipitation, and visibility?
Stable air: stratiform clouds, smooth air, steady precipitation, poor visibility.
What are the effects of unstable air on clouds, turbulence, precipitation, and visibility?
Unstable air: cumuliform clouds, rough air, showery precipitation, good visibility.
What are the two main categories of aircraft icing?
Structural icing and induction icing.
What are the three types of structural ice that may occur in flight?
Clear ice, rime ice, and mixed ice.
What is clear ice, and under what conditions does it form?
Clear ice is glossy, translucent ice formed by slow freezing of large droplets in warmer conditions.
What is rime ice, and under what conditions does it form?
Rime ice is rough, opaque ice formed by the rapid freezing of small droplets in colder conditions.
What is mixed ice, and how does it form?
Mixed ice is a combination of clear and rime ice, forming under intermediate conditions.
What types of icing are found in stratiform clouds?
Rime and mixed ice, typically in layers 3,000 to 4,000 feet thick.
What types of icing are found in cumuliform clouds?
Clear or mixed ice, usually concentrated in the upper levels.
What conditions are necessary for structural icing to occur?
Visible water and temperatures at or below 0°C.
What are the intensity categories of aircraft structural icing?
Trace, light, moderate, and severe.
What characterizes ‘trace’ aircraft structural icing?
Ice is noticeable, but the accumulation rate is slightly greater than sublimation.
What characterizes ‘light’ aircraft structural icing?
Ice accumulates at ¼ to 1 inch per hour, requiring occasional deicing.
What characterizes ‘moderate’ aircraft structural icing?
Ice accumulates at 1 to 3 inches per hour, requiring frequent deicing.
What characterizes ‘severe’ aircraft structural icing?
Ice protection systems fail to remove ice; accumulation exceeds 3 inches per hour.
What meteorological information should you check preflight to avoid icing?
Front locations, cloud layers, freezing levels, temperatures, and precipitation.
What is the definition of ‘freezing level’?
The lowest altitude where the air temperature reaches 0°C.
How can you determine the freezing level location?
Use GFA, PIREPs, AIRMETs, SIGMETs, and other aviation weather products.
How can you mitigate the risk of operating in or near icing conditions during preflight planning?
Consider climb performance, icing exit strategies, fuel requirements, and alternate airports with longer runways.
What factors are necessary for a thunderstorm to form?
Sufficient water vapor, an unstable lapse rate, and an initial upward lift.
What are the three stages of thunderstorm development?
Cumulus (updrafts), mature (precipitation, updrafts, and downdrafts), and dissipating (downdrafts).
What is a squall line?
A non-frontal narrow band of active thunderstorms, often severe, usually forming ahead of a cold front.
How does fog form?
Fog forms when the temperature and dew point become identical or nearly identical.
What are several types of fog?
Radiation, advection, upslope, frontal (precipitation-induced), and steam fog.
What causes radiation fog to form?
Clear skies, little or no wind, and high humidity at night or near daybreak.
What is advection fog, and where is it most likely to form?
Advection fog forms when moist air moves over colder ground or water, common in coastal areas.
What causes upslope fog to form?
Moist, stable air moving up sloping terrain and cooling adiabatically.
What is steam fog, and how does it form?
Steam fog forms when cold air moves over warmer water, causing rising moisture to condense into fog.
How does frontal (precipitation-induced) fog form?
Warm, moist air lifted over a front causes precipitation; evaporation saturates cold air near its dew point, forming fog.
What are some common IFR weather producers besides fog?
Low clouds (stratus), haze, smoke, blowing obstructions, and precipitation.
How can you obtain a good weather briefing prior to a flight?
Watch weather forecasts, use Flight Service, download weather charts, and get a standard briefing close to departure.
What are some examples of other sources of weather information?
Leidos Flight Services, private industry sources, and FIS-B via ADS-B In.
What should a weather briefing include?
Adverse conditions, VFR not recommended, synopsis, current conditions, forecasts, winds aloft, NOTAMs, ATC delays.
How can a pilot obtain updated weather information while en route?
Contact FSS, use ATIS/ASOS/AWOS, datalink weather, or ask ATC.
What is Flight Information Service–Broadcast (FIS-B)?
A service that provides aviation weather and aeronautical information via ADS-B to properly equipped aircraft.
