AVIATION WEATHER QUESTIONS & ANSWERS
What are the characteristics of the flow of air around high pressure systems? - Answers
:Outward
Downward
Clockwise
What are the characteristics of the flow of air around low pressure systems? - Answers
:Inward
Upward
Counterclockwise
What is a Trough Line? - Answers :An elongated area of low pressure.
(Air rises in this area)
(It is conducive to cloudiness and precipitation)
What is a Ridge Line? - Answers :An elongated area of high pressure.
(Air moving out of a high depletes the quantity of air - therefore these are areas of
descending air.)
(Descending air favors dissipation of cloudiness)
What are isobars? - Answers :Lines on a weather chart which connect areas of equal or
constant barometric pressure.
If isobars are close together on a weather chart or a constant pressure chart what does
this mean? - Answers :This shows the steepness of the pressure gradient.
• Close = Steep Pressure Gradient = High Wind Speeds
• Spaced Out = Shallow PG = Low Wind Speeds
What causes the winds aloft to flow parallel to the isobars? - Answers :Coriolis Force
What causes surface winds to generally flow across the isobars at an angle? - Answers
:Surface Friction
What is the effect of stable air on clouds? - Answers :Stratiform
What is the effect of unstable air on clouds? - Answers :Cumuliform
What is the effect of stable air on turbulence? - Answers :Smooth
What is the effect of unstable air on turbulence? - Answers :Rough
What is the effect of stable air on precipitation? - Answers :Steady
What is the effect of unstable air on precipitation? - Answers :Showery
, What is the effect of stable air on visibility? - Answers :Fair to Poor
What is the effect of unstable air on visibility? - Answers :Good
At what rate does atmospheric pressure decrease with an increase in altitude? -
Answers :1in. Hg per 1,000 ft.
How do you determine the stability of the atmosphere? - Answers :By observing the
actual lapse rate and comparing it to the standard lapse rate of 3.5° F (2° C) per 1000 ft.
(In general stable air cools at a rate less than the standard lapse rate with altitude)
The "K" index of a stability chart is the primary means of determining stability.
What are the stages of a thunderstorm? - Answers :1. Cumulus - Updrafts cause
raindrops to increase in size
2. Mature - Rain at Earth's surface (it falls through or immediately beside the updrafts);
Lightning; perhaps roll clouds
3. Dissipating - Downdrafts and rain begin to dissipate
What factors must be present for thunderstorms to form? - Answers :1. A source of lift
(heating, fast-moving front)
2. Unstable Air (nonstandard lapse rate)
3. High Moisture Content (temp. and dew point close)
Is frost considered hazardous to flight? - Answers :Yes.
(Because it causes friction... The friction interrupts the airflow that generates lift)
What action should be taken if you inadvertently encounter icing conditions? - Answers
:Change course and/or altitude. (Usually, climb to a higher altitude if possible)
What are the main types of icing? - Answers :• Structural
• Induction
Name 4 types of structural Ice. - Answers :1. Frost - Ice crystals from sublimation when
temp and dew point are below freezing
2. Clear - Large drops freeze slowly
3. Rime - Small drops freeze rapidly
4. Mixed - Supercooled drops varying in size
What conditions are necessary for structural icing to occur? - Answers :• Visible
Moisture
• Below Freezing Temperatures
(At the point where moisture strikes the aircraft)
What are the characteristics of the flow of air around high pressure systems? - Answers
:Outward
Downward
Clockwise
What are the characteristics of the flow of air around low pressure systems? - Answers
:Inward
Upward
Counterclockwise
What is a Trough Line? - Answers :An elongated area of low pressure.
(Air rises in this area)
(It is conducive to cloudiness and precipitation)
What is a Ridge Line? - Answers :An elongated area of high pressure.
(Air moving out of a high depletes the quantity of air - therefore these are areas of
descending air.)
(Descending air favors dissipation of cloudiness)
What are isobars? - Answers :Lines on a weather chart which connect areas of equal or
constant barometric pressure.
If isobars are close together on a weather chart or a constant pressure chart what does
this mean? - Answers :This shows the steepness of the pressure gradient.
• Close = Steep Pressure Gradient = High Wind Speeds
• Spaced Out = Shallow PG = Low Wind Speeds
What causes the winds aloft to flow parallel to the isobars? - Answers :Coriolis Force
What causes surface winds to generally flow across the isobars at an angle? - Answers
:Surface Friction
What is the effect of stable air on clouds? - Answers :Stratiform
What is the effect of unstable air on clouds? - Answers :Cumuliform
What is the effect of stable air on turbulence? - Answers :Smooth
What is the effect of unstable air on turbulence? - Answers :Rough
What is the effect of stable air on precipitation? - Answers :Steady
What is the effect of unstable air on precipitation? - Answers :Showery
, What is the effect of stable air on visibility? - Answers :Fair to Poor
What is the effect of unstable air on visibility? - Answers :Good
At what rate does atmospheric pressure decrease with an increase in altitude? -
Answers :1in. Hg per 1,000 ft.
How do you determine the stability of the atmosphere? - Answers :By observing the
actual lapse rate and comparing it to the standard lapse rate of 3.5° F (2° C) per 1000 ft.
(In general stable air cools at a rate less than the standard lapse rate with altitude)
The "K" index of a stability chart is the primary means of determining stability.
What are the stages of a thunderstorm? - Answers :1. Cumulus - Updrafts cause
raindrops to increase in size
2. Mature - Rain at Earth's surface (it falls through or immediately beside the updrafts);
Lightning; perhaps roll clouds
3. Dissipating - Downdrafts and rain begin to dissipate
What factors must be present for thunderstorms to form? - Answers :1. A source of lift
(heating, fast-moving front)
2. Unstable Air (nonstandard lapse rate)
3. High Moisture Content (temp. and dew point close)
Is frost considered hazardous to flight? - Answers :Yes.
(Because it causes friction... The friction interrupts the airflow that generates lift)
What action should be taken if you inadvertently encounter icing conditions? - Answers
:Change course and/or altitude. (Usually, climb to a higher altitude if possible)
What are the main types of icing? - Answers :• Structural
• Induction
Name 4 types of structural Ice. - Answers :1. Frost - Ice crystals from sublimation when
temp and dew point are below freezing
2. Clear - Large drops freeze slowly
3. Rime - Small drops freeze rapidly
4. Mixed - Supercooled drops varying in size
What conditions are necessary for structural icing to occur? - Answers :• Visible
Moisture
• Below Freezing Temperatures
(At the point where moisture strikes the aircraft)
