Weather Flashcards
What are the general characteristics in regard to flow of air around a high pressure system?
Outward, Downward, and Clockwise.
What are the general characteristics in regard to flow of air around a low pressure system?
Inward, Upward, and Counterclockwise.
Describe the different types of fronts.
Cold Front - Occurs when a mass of cold, dense, and stable air advances and replaces a body of warmer air.
Warm Front - The boundary area formed when a warm air mass contacts and flows over a colder air mass.
Occluded Front - A frontal occlusion occurs when a fast-moving cold front catches up to a slow moving warm front.
Stationary Front - When the forces of two air masses are relatively equal, the boundary or front that separates them remains stationary and influences the local weather for days. The weather is typically a mixture of both warm and cold fronts.
What are the general weather characteristics associated with a cold front?
The expected weather can include towering cumulus or cumulonimbus clouds, heavy rain, lightning, tornadoes, poor visibility, winds variable and gusting, sudden drop in temperature and dew point as well as barometric pressure. In other words, really shitty weather.
What are the general weather characteristics associated with a warm front?
The expected weather can include stratiform clouds, drizzle, low ceilings and poor visibility; variable winds; rise in temperature. Not as shitty as a cold front.
What is a trough?
An elongated area of relatively low atmospheric pressure. The air tends to rise in a trough resulting in cloudiness and poor VFR weather.
What is a ridge?
An elongated area of relatively high atmospheric pressure. The air tends to descend in a ridge resulting in dissipation of cloudiness, making good visibility and VFR weather.
What are the standard temperature and pressure values for sea level?
15 degrees Celsius and 29.92 inches of Mercury.
What are isobars?
Isobars are lines on a weather chart which connects areas of constant or equal barometric pressure.
What do the spacing of the isobars indicate?
If they isobars are closer together, it means there is a steeper pressure gradient which results in higher wind velocity. If the isobars are further apart, it means there is a shallower pressure gradient resulting in less high wind velocities.
What causes the winds aloft to flow parallel to the isobars?
The Coriolis Force
Why do surface winds generally flow across the isobars at an angle?
Surface Friction
At what rate does atmospheric pressure decrease with an increase in altitude?
1” Hg per 1,000’
What does “dew point” mean?
Dew point is the temperature to which a sample of air must be cooled to attain a state of saturation.
When temperature and dew point are close together (within 5 degrees), what type of weather is likely?
Visible moisture in the form of clouds, dew, or fog. These are also ideal conditions for carburetor icing.
What factor primarily determines the type and vertical extent of clouds?
The stability of the atmosphere.
Explain the difference between a stable atmosphere and an unstable atmosphere.
The stability of the atmosphere depends on its ability to resist vertical motion. A stable atmosphere makes vertical movement difficult, and small vertical disturbances dampen out and disappear. In an unstable atmosphere, small vertical movements tend to become larger, resulting in turbulent airflow and convective activity. Instability can lead to significant turbulence, extensive vertical clouds, and severe weather.
List the effects of stable and unstable air on clouds, turbulence, precipitation, and visibility.
Stable: - Clouds : Stratiform - Turbulence : Smooth - Precipitation : Steady - Visibility : Poor Unstable - Clouds : Cumuliform - Turbulence : Rough - Precipitation : Showery - Visibility : Good
During preflight planning, what type of meteorological information should you be aware with respect to icing?
Location of Fronts : A front’s location, type, speed, and direction of movement.
Cloud Layers : The location of cloud bases and tops, which is valuable when determining if you will be able to climb above icing layers or descend beneath those layers into warmer air; reference PIREPs and Area Forecasts.
Freezing Levels : Important when determining how to avoid icing and how to exit icing conditions if accidentally encountered.
Air Temperature and Pressure : Icing tends to be found in low-pressure areas and at temperatures at or around freezing.
What conditions are necessary for structural icing to occur?
Visible moisture and below freezing temperatures at the point moisture strikes the aircraft.
Name the main types of icing an aircraft may encounter in-flight.
- Structural
- Induction System
- Instrument
Name the three types of structural icing that may occur in flight.
Clear Ice - Forms after initial impact when the remaining liquid portion of the drop flows out over the aircraft surface, gradually freezing as a smooth sheet of solid ice.
Rime Ice - Forms when drops are small, such as those in stratified clouds or light drizzle. The liquid portion remaining after initial impact freezes rapidly before the drop has time to spread out over aircraft surface. The air gets trapped in the ice creating a white hue.
Mixed Ice - A mixture of clear and rime.
What action is recommended if you inadvertently encounter icing conditions?
Leave the area of visible moisture. Either descend, climb or turn to a different course.
Is frost hazardous to flight?
Yes, because it spoils the smooth airflow, thus causing a slower airflow and less lift.
What factors must be present for a thunderstorm to form?
- Sufficient water vapor
- An unstable lapse rate
- An initial upward lifting force to start the storm process in motion.
