Weather Theory Flashcards
Most of the Earth’s weather occurs in what region of the atmosphere?
Troposphere - surface up to 36,000ft
Standard temp and pressure at sea level
15 celcius / 59 farenheit
1013.2 mb / 29.92” Hg
What are isobars?
a line on a weather chart that connects areas of equal or constant barometric pressure
If isobars are close together on a surface weather chart or constant weather chart, what does that tell you??
spacing of isobars shows how steep or shallow the pressure gradient is. When they are tight, a steep gradient exists and means higher wind speeds. shallow = not close together = lower wind
Whats dew point?
temp to which a sample of air must be cooled to become saturated
How does fog form?
temp = dew point or nearly so.
cooling of air to a little beyond dewpoint (radiation, advection, upslope fog) or by adding moisture and elevating the dewpoint (frontal or steam fog)
What factor determines the type and vertical extent of clouds?
stability of atmosphere
Explain diff. between stable and unstable atmosphere. Why is stability important?
stability depends on its ability to resist vertical motion. stable atmosphere makes vertical movement more difficult, and small vertical disturbances dampen out or disappear.
unstable, small vertical movements grow resulting in turbulent airflow and convective activity.
How can you determine the stability of the atmosphere?
When temp decreases uniformly and rapidly as you climb (approaching 3c per 1,000 feet) you have an indication of unstable air. If unchanged or decreases slightly with altitude, more stable. When surface air is warm and moist, probably unstable
stable vs. unstable air on clouds, turbulence, precipitation, visibility
stable: stratiform clouds, smooth air, steady precip, fair to poor visibility
unstable: cumuliform clouds, rough air, showery precip, good visibility
general characteristics of flow of air around high/low pressure systems
low - inward, upward, counterclockwise
high, outward, downward, clockwise
general expectations flying into a low pressure system. High pressure?
low - rising air which is conductive to cloudiness, precipitation, bad weather.
high - descending air which favors dissipation of cloudiness and good weather
Describe different types of fronts
cold - mass of cold dense stable air advances to replace a body of warmer air
occluded - occurs when a fast moving cold front catches up with a slow moving warm front (can be cold front occlusion and warm front occlusion)
warm - boundary area formed when a warm air mass contacts and flows over a colder air mass
stationary - when the forces of 2 air masses are relatively equal, the front that separates them remains stationary and influences local weather for days. typically a mix of warm and cold front weather
General characteristics of weather encountered when operating near a cold and warm front
cold - as the front passes, towering cumulus or cumulonimbus, heavy rain/lightning/thunder.hail even tornadoes, poor visibility, wind variable and gusting, temp/dew point and pressure drop rapidly
warm - as the front passes, stratiform clouds, drizzle, low ceilings, poor visibility, variable winds, rise in temp
both depend on available moisture, stability of air forced upward, slope of the front, speed of movement, and upper wind flow
What is a trough?
elongated area of relatively low pressure / in an area of rising air. conducive to cloudiness and precip.
