Weather Information Flashcards
state the general characteristics in regard to the flow of air around high and low pressure systems in the northern hemisphere
low pressure - inward, upward, and counterclockwise
high pressure - outward, downward, and clockwise
if your route of flight takes you towards a low-pressure system, in general, what kind of wether can you expect? What if you were flying towards a high-pressure system?
a low-pressure system is characterized by rising air, which is conductive to cloudiness, precipitation and bad weather. A high-pressure system is an area of descending air which tends to favor dissipation of cloudiness and good weather
describe the difference types of fronts
cold front - occurs when a mass of cold, dense, and stable air advances and replaces a body of warmer air (blue cones)
occluded front - a frontal occlusion occurs when a fast moving cold front catches up with a slow-moving warm front. Two types: cold front occlusion and warm front occlusion (purple - cold = cold > warm > cool - warm = cool > warm > cold)
warm front - the boundary area formed when a warm air mass contacts and flows over a colder air mass (red half suns)
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 characteristics of the weather a pilot would encounter when operating near a cold front? a warm front?
cold front - as the front passes, expected weather can include towering cumulus or cumulonimbus, heavy rain accompanied by lighting, thunder and/or hail; tornadoes possible; during passage, poor visibility, winds variable and gusting; temperature/dew point and barometric pressure drop rapidly
warm front - as the front passes, expected weather can include stratiform clouds, drizzle, low ceilings and poor visibility; variable winds; rise in temperature.
weather associated depends on amount of moisture available, degree of stability of Air Forced upward, slope of the front, the speed of frontal movement, and upper wind flow
what is a trough
a trough - is an elongated area of relatively low atmospheric pressure. At the surface when air converges into a low, it cannot go outward against the pressure gradient, nor can it go downward into the ground; it must go upward. Therefore, a low or trough is an area of rising air. Rising air is conducive to cloudiness and precipitation; hence the general association of low pressure and bad weather
what is a ridge
an elongated are of relatively high atmospheric pressure. Air moving out of a high or ridge depletes the quantity of air; therefore, these are areas of descending air. Descending air favors dissipation of cloudiness; hence the association of high pressure and good weather
what are the standard temperature and pressure values for sea level
59 degrees F
15 degrees C
29.92 “ Hg
1013.2 millibars
what are isobars
an isobar is a line on a weather chart which connects areas of equal or constant barometric pressure
if the isobars are relatively close together on a surface weather chart or a constant pressure chart, what information will this provide
The spacing of isobars on these charts defines how steep or shallow a pressure gradient is. When isobars are spaced very close together, a steep pressure gradient exists which indicates higher wind speeds. A shallow pressure gradient usually means wind speeds will be less
what is the name of the force that deflects winds to the right in the northern hemisphere and left in the Southern Hemisphere
the Coriolis force. It is at the right angle to wind direction and is directly proportional to wind speed.
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 feet
what does dew point mean
dew point is the temperature to which a sample of air must be cooled to attain the state of saturation
when temperature and dew point are close together (within 5 degree) what type of weather is likely
visible moisture in the form of clouds, dew, or fog. Also, these are ideal conditions for carburetor icing
what factor primarily determines the type and vertical extent of clouds
the stability of the atmosphere
