Aviation Weather Flashcards
What causes variations in altimeter settings between weather reporting points?
Unequal heating of the Earth’s surface
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
Convective circulation patterns associated with sea breezes are caused by
cool, dense air moving inland from over the water
The development of thermals depends upon
solar heating
The boundary between two different air masses is referred to as
font
One weather phenomenon which will always occur when flying accros a front is a change in teh
wind direction
One of the most easily recognized discontinuities across a front is
a change in temperture
If there is thunderstorm activity in the vicinity of an airport at which you plan to land, which hazardous atmospheric phenomenon might be expected on the landing approach?
Wind shear turbelance
A nonfrontal, narrow band of active thunderstorms that often develop ahead of a cold front is know as a
squall line
what conditions are necessary for the formation of thunderstorms?
High humidity, lifting force, and unstable conditions
During the life cycle of a thunderstorm, which stage is characterized predominately by downdrafts>
Dissipating
Thunderstarms reach their greates intensity during
mature stage
What feature is normally associated witht eh cumulus stage of a thunderstorm?
continuous updraft
Which weather phenomenon signals the beginning of teh mature stage of a thunderstorm?
Precipitation beginning to fall
Thunderstorms which generally produce the most intense hazard to aircraft are
squall line thunderstorms
Which weather phenomenon is always associated with thunderstorm?
Lightening
One inflight condition necessary for structureal icing to form is
visible mositure
In which envireonment is aircraft sturctural ice most likely to have the ightes accumulation rate?
Freezing rain
The presence of ice pellets at the surface is eveidence that there
is a temperture inversion with freezing rain at a higher altitude
An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 knots or more, is refered to as
a lenticular cloud
Crests of standing mountain waves may be marked by stationary, lens shaped clouds known as
standing lenticular clouds
Possible mountain wave turbulence coudl be anticipated when winds of 40 knots or greater blow
across a mountain ridge, and the air is stable
Where does wind shear occur>
At all altitudes in all directions
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
When may hazardous wind shear be expected?
In areas of low level temperature inversion frontal zones and clear air turbulence
If the temperature/dewpoint spread is smaill and decreasing, and the temperature is 62 degrees F, what type weather is most likely to develop?
Fog or low clouds
What is meatn by the term “dewpoint?”
The temperture to which air must be cooled to become saturated
The amount of water vapor which air can hold depends on the
air temperature
What are the processes by which moisture is added to unsaturated air?
Evaporation and sublimation
Which conditions result in the formation of frost?
The temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing
Clouds, fog, or dew will always form when
water vapor condenses
Low level turbulence can occur and icing can become hazardous in wich type of fog?
steam fog
In which situation is advection fog most likely to form?
An air mass moving inland from the coast in winter
What situation is most conducive to the formation of radiation fog?
Warm, moist air over low, flatland areas on clear, calm nights
What tupes of fog depend upon wind in order to exist?
Advection fog and upslope fog
Clouds are divided into four families according to their
height range
The suffix “nimbus” used in naming clouds, means
a rain cloud
The conditions necessary for the formation of cumulonimbus clouds are lifting action and
unstable, moist air
What clouds have the greatest turbulence?
Cumulonimbus
What cloud types would indicate convective turbulence?
Towering cumulus clouds
At approximately what altitude above the surface would the pilot expect teh base of cumuliform clouds if the surface air temperture is 82 degrees F and teh dewpoint is 38 degrees F?
10,000 feet AGL
What is the approximate base of the cumulus clouds if the surface air temperture is at 1,000 feet MSL is 70 degrees F and teh dewpoint is 48 degrees F?
6,000 feet MSL
What is a characteristic of stable air?
Stratiform clouds
Moist stable air flowing upslope can be expected to
produce stratus type clouds
If an unstable air mass is forced upward, what type of clouds can be expected?
Clouds with considerable vertical development and associated turbulence
What are characteristics of unstable air?
Turbulence and good surface visibility
A stable air mass is most likely to have whihc characteristic?
Poor surface visibility
Steady precipitation preceding a front in an indicatin of
stratiform clouds with little or no turbulence
What are characteristics of a moist unstable air mass?
Cumuliform clouds and showery precipitation
What measurement can be used to determine the stability of the atmosphere?
Actual lapse rate
What would decrease the stability of an air mass?
Warming from below
What feature is associated with a temperature inversion
A stable layer of air
The most frequent type of ground or surface based tempertaure inversion is that which is produced by
terrestrial radiation on a clear, relatively still night
A temperature inversion would most liekly result in which weather condition?
An increased in temperature as altitude is increased
Which weather condtions shuld be expected beneath a low level temperature inversion layer when the relative humidy is high?
Smooth air, poor visibility, fogm haze, or low clouds
