Weather Flashcards
What conditions can be expected in an area of low pressure
Low pressure moves air upwards, tending to form clouds and offering the potential for precipitation. High pressure dissipate cloud formations, usually resulting in better conditions.
Name the different types of fronts
Cold Front - body of cold, dense air replaces a warmer air mass
Occluded Front - when a fast moving front catches up and overtakes a slower moving front
Warm Front - the boundary where a warm air mass flows over a colder air mass
Stationary Front - when the force of two air masses is relatively equal, the front that separates them remains stationary.
What is a trough
An area of low pressure. The air has a tendency to rise since it can’t go underneath the ground, so this rising air has the potential to create clouds.
What is a ridge
A line or boundary layer of high pressure; usually associated with good weather as cloud layers have difficulty forming with sinking air.
What are isobars?
Isobars indicate the steepness of a pressure gradient, and subsequently wind speeds. Isobars that are close together produce stronger winds and indicates a steep pressure gradient. A steep pressure gradient implies that the pressure of an area changes rapidly over a short distance.
Define dew point
The temperature at which air will become saturated.
How thick must clouds be to create significant precipitation?
Clouds must be at least 4,000 feet thick to produce rain/precipitation.
How do you avoid icing when planning a flight
1) Look at Zulu airmets and pireps
2) pay attention to low pressure areas (these will likely have lower forming clouds)
3) The location of cloud bases and tops
4) Realize and locate freezing levels along the flight path
What are the two categories of icing? What are three types of structural ice?
Categories:
1) Structural (forming along the aircraft)
2) Induction (engine)
Types:
1) Rime - freezing occurs at the upflow, or the leading edge, of the wing camber
2) Clear - freezing occurs downflow or more towards the trailing edge of the wing
3) Mixed - combination of rime and clear
If ice starts to form, what should be done?
Deviate from any area of visible moisture; below or above cloud tops.
What three ingredients need to exist for a storm to occur?
1) Sufficient amounts of moisture/water vapor
2) Uplifting air
3) Unstable lapse rate
Name the 3 stages of a thundetstorm
Cumulus Stage - Cumulus clouds build from continous updrafts
Maturing Stage - When the updrafts begin to produce precipitation
Dissipiating Stage - The downdrafts from the precipitation causes the storm to dissipate
Describe a temperature inversion
When the atmosphere becomes warmer at a higher elevation. An increase of temperature with height. Ground based inversions causes the warm air to trap fog and haze near the ground.
When does fog form?
When the temperature and dewpoint come close to matching, fog will result. This occurs from the cooling of the air to reach the dewpoint (radiation fog, upslope fog, advection fog) or from moisture being added to the air, raising the dewpoint temperature (frontal fog, steam fog).
Name the different types of fog
Advection Fog - warm, humid air drifts over a cool surface. Occurs along coastal areas at anytime, usually in winter.
Steam Fog - when moisture from warm water evaporates into colder air above it
Frontal Fog - rain falling from warm air to cool air can cause fog to form.
Upslope Fog - when upslope wind cause most air to cool, causing dense fog to form at higher altitudes.
Radiant Fog - the ground cools the air to the dewpoint on a calm, clear night
