weather Flashcards
The amount of water vapor which air can hold depends on the
air temperature.
If an unstable air mass is forced upward, what type clouds can be expected?
Clouds with considerable vertical development and associated turbulence.
When may hazardous wind shear be expected?
In areas of low-level temperature inversion, frontal zones, and clear air turbulence.
A pilot can expect a wind shear zone in a temperature inversion whenever the windspeed at 2,000 to 4,000 feet above the surface is at least
25 knots.
What types of fog depend upon wind in order to exist?
Advection fog and upslope fog.
What situation is most conducive to the formation of radiation fog?
Warm, moist air over low, flatland areas on clear, calm nights.
One weather phenomenon which will always occur when flying across a front is a change in the
wind direction.
The most frequent type of ground or surface-based temperature inversion is that which is produced by
terrestrial radiation on a clear, relatively still night.
When there is a temperature inversion, you would expect to experience
an increase in temperature as altitude increases.
Which weather phenomenon signals the beginning of the mature stage of a thunderstorm?
Precipitation beginning to fall.
The mature stage of a thunderstorm begins with
the start of precipitation.
Which weather phenomenon is always associated with a thunderstorm?
Lightning.
Low-level turbulence can occur and icing can become hazardous in which type of fog?
Steam fog.
What feature is associated with a temperature inversion?
A stable layer of air.
When warm, moist, stable air flows upslope, it
produces stratus type clouds.
Steady precipitation preceding a front is an indication of
stratiform clouds with little or no turbulence.
Every physical process of weather is accompanied by, or is the result of, a
heat exchange.
A nonfrontal, narrow band of active thunderstorms that often develop ahead of a cold front is known as a
squall line.
Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?
Smooth air, poor visibility, fog, haze, or low clouds.
What clouds have the greatest turbulence?
Cumulonimbus.
Possible mountain wave turbulence could be anticipated when winds of 40 knots or greater blow
across a mountain ridge, and the air is stable.
What would decrease the stability of an air mass?
Warming from below.
Clouds, fog, or dew will always form when
water vapor condenses.
In which situation is advection fog most likely to form?
An air mass moving inland from the coast in winter.
The conditions necessary for the formation of cumulonimbus clouds are a lifting action and
unstable, moist air.
The suffix ‘nimbus,’ used in naming clouds, means
a rain cloud.
Which conditions result in the formation of frost?
The temperature of the collecting surface is at or below the dew point of the adjacent air and the dew point is below freezing.
The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to
friction between the wind and the surface.
At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82°F and the dew point is 38°F?
Step 1: 82°F (Surface temperature) – 38°F (Dew point) = 44°F
Step 2: 44 ÷ 4.4 = 10
Step 3: 10 × 1,000 = 10,000 feet AGL (base of cloud)
10,000 feet AGL. When lifted, unsaturated air cools at approximately 5.4°F per 1,000 feet. The dew point cools at approximately 1°F per 1,000 feet. Therefore, the convergence of the temperature and dew point lapse rates is 4.4°F per 1,000 feet. The base of a cloud (AGL) that is formed by vertical currents 10 3. 10 x 1,000 = 10,000 feet AGL
Which type of weather briefing should a pilot request to supplement mass disseminated data?
An abbreviated briefing.
What is indicated when a current Convective SIGMET forecasts thunderstorms?
Thunderstorms obscured by massive cloud layers
To best determine general forecast weather conditions covering a flight information region, the pilot should refer to
Graphical Forecasts for Aviation (GFA).
SIGMETs are issued as a warning of weather conditions hazardous to which aircraft?
All aircraft.
When the term ‘light and variable’ is used in reference to a winds aloft forecast, the coded group and windspeed is
9900 and less than 5 knots.
What information is contained in a Convective SIGMET?
Tornadoes, embedded thunderstorms, and hail 3/4 inch or greater in diameter.
What should pilots state initially when telephoning Flight Service for preflight weather information?
Identify themselves as pilots.
What values are used for winds aloft forecasts?
True direction and knots.
AIRMETs are advisories of significant weather phenomena but of lower intensities than SIGMETs and are intended for dissemination to
all pilots.
Which inflight advisory would contain information on severe icing not associated with thunderstorms?
SIGMET.
