Weather Flashcards
Why should you slow down during turbulence?
The airplane will stall before exceeding the load limit
Gust load factors increase with speed, slowing can help limit these load factors
What feature is associated with the tropopause?
Abrupt change in the temperature lapse rate
A defining characteristic of the stratosphere is
relatively small change in temperature with altitude
Surface based temperature inversions typically develop
by ground radiation on clear, cool nights when the wind is light
The ground radiates and cools much faster than the overlying air. Air in contact with the ground becomes cool and the air a few hundred feet up changes little
What is the standard lapse rate for temperature?
2 degrees Celsius / 1,000 ft
What is the standard temperature at sea level
15 degrees Celsius
The primary cause of all changes in the Earth’s weather is
variation of solar energy–uneven heating of Earth’s surface
What feature is associated with a temperature inversion
A stable layer of air
What weather condition would you expect beneath a low level temperature inversion when relative humidity is high?
Smooth air and poor visibility due to fog, haze, and low clouds
What do winds normally flow parallel to?
Isobars
Why do surface winds not always flow parallel to the isobars
surface friction
What force acts at a right angle to weather and deflects it to the right in the Northern Hemisphere and vice versa for the Southern Hemisphere?
Coriolis force
When is hazardous wind shear commonly encountered near the ground?
during periods of strong temperature inversions and near thunderstorms
The presence of ice pellets, or hail, at the surface is evidence that at a higher altitude there is
freezing rain
What is ‘dew point’?
The temperature at which the air must be cooled to become saturated
The presence of wet snow at your flight altitude indicates that the freezing level is
above you
What enhances the growth rate of precipitation
Upward currents… Convective action
What types of clouds will form if very stable, moist air is forced upslope
Stratified clouds with little vertical development
Stability can be determined from what measurement of the atmosphere?
Ambient lapse rate
The suffix ‘nimbus’ in clouds means
rain cloud
What are the four families of clouds?
High, middle, low, and those with extensive vertical development
A high cloud is composed mostly of
ice crystals
Steady precipitation, in contrast to showers, preceding a front is an indication of
stratiform clouds, aka stable air with little or no turbulence
General characteristics of unstable air are
good visibility, showery precipitation, and cumuliform type clouds, turbulence
General characteristics of stable air are
fair to poor visibility, continuous precipitation, stratiform clouds and fog, smooth air
Frontal waves normally form on
slow moving cold fronts or stationary fronts
What weather phenomenon is always associated with the passage of a frontal system?
A wind change
If standing lenticular clouds are seen over a mountainous area, a pilot should
be aware of severe mountain wave turbulence
A tailwind that quickly changes to a headwind would cause
an increase of airspeed and performance
A headwind that quickly changes to a tailwind would cause
a decrease of airspeed and performance
Turbulence, for cumulus clouds, is located
at and below the cloud level
Wind shear is an atmospheric condition that may be associated with
low level temperature inversions, a jet stream, or a frontal zone
Which family of clouds is least likely to contribute to structural icing on an aircraft?
High clouds
Where do squall lines most often develop?
Ahead of a cold front
Which stage of a thunderstorm is characterized primarily by downdrafts?
Dissipating
Which stage of a thunderstorm is characterized by rain at the surface
Mature
What weather phenomenon is always associated with a thunderstorm?
Lightning
What thunderstorms generally produce the most severe conditions?
Squall lines
What are the requirements for the formation of a thunderstorm?
Sufficient moisture, an unstable lapse rate, and a lifting action
T or F: Airborne weather avoidance radar can help avoid clouds and fog without precipitation
False!
Airborne weather avoidance radar can only detect echoes of where precipitation is concurring. It cannot detect minute clouds and fog without precipitation
Advection fog usually forms from
moist air moving over colder ground or water
Fog is usually prevalent in industrial areas because of
an abundance of condensation nuclei from combustion products
Where is advection fog most likely to form?
An air mass moving inland from the coast in winter
What types of fog depend upon a wind in order to exist?
Advection fog and up slope fog
Where and when does radiation fog usually form
Warm, moist air over low, flatland areas on clear, calm nights
What conditions are favorable for the formation of radiation fog?
Clear sky, little or no wind, small temperature/dew point spread, and over a land surface
A jet stream is defined as wind of
50 knots or greater
What is HIWAS and what does it do?
Hazardous Inflight Weather Advisory Service
is a continuous broadcast over selected VORs of SIGMETs, Convective SIGMETs, AIRMETs, Severe Weather Forecasts Alerts (AWW), and Center Weather Advisories
A ceiling is defined as
the lowest layer of clouds or obscuring phenomena aloft that is reported as BROKEN or OVERCAST
The body of TAF covers a proximity within
5 statute miles from the center of the airport runway complex
TWEB’s (Transcribed Weather Broadcast) provide what information
Sky Cover, Cloud tops, Weather, and obstructions to vision in a route format
When are severe weather watch (WW) bulletins issued
Unscheduled and issued as required.
Defines areas of possible severe thunderstorms and tornados
What is the maximum forecast period for AIRMETs
6 hours
Area forecasts generally include a forecast period of …. and cover a geographical area the size of ….
18 hours
area the size of several states
You can expect to see an operating rotating beacon at an airport during daylight when the ceiling and visibility are reported below
1,000ft and 3 miles
When are ATIS broadcasts updated
whenever they receive any official weather updates regardless of content change
Absence of sky condition and visibility on an ATIS specifically implies that
the ceiling is more than 5,000 ft and the visibility more than 5 miles
What is the expected duration of a microburst
Seldom more than 15 minutes
Maximum downdrafts in a microburst may be as strong as
6,000 ft per minute
A temperature inversion will normally form only
in stable air
Convective SIGMETs are valid for `
2 hours
You encounter freezing drizzle at your flight altitude, this is a good indication that there is
warmer air above you
US SIGMETS are issued what phenomena occur or are expected to occur?
Severe icing not associated with thunderstorms
Severe or extreme turbulence or clear air turbulence not associated with thunderstorms
Dust storms or sandstorms lowering visibility below 3 miles
Volcanic ash
If you encounter wet snow at your altitude, this is a good indication that
the temperature is above freezing at your altitude
While flying with the autopilot engaged, you encounter structural icing. You should be aware that
you may want to disengage the autopilot and hand fly the airplane
