Pressures And Winds Flashcards
Isobars
Lines connecting points of equal pressure corrected to sea level
Spaced 4 mb apart
Pressure Gradient Force
Rate at which air will accelerate depends on rate at which pressure changes with distance.
Isobar Spacing
Isobars closely spaced – strong or steep pressure gradient, moderate to strong winds
Isobars widely spaced – weak or flat pressure gradient, calm or light winds
Before Coriolis Force takes effect, in which direction do winds move?
High pressure to low pressure
What causes wind speed?
Pressure Gradient Force
Coriolis Force
An apparent deflective force resulting from the Earth’s rotation
Coriolis Force
Characteristics
Acts perpendicular to wind
Proportional to wind speed
Strongest at poles
Zero at equator
High pressure rotates
Clockwise and parallel to the isobars
Below 2000 feet
Diverges approximately 30 degrees from the center
Low pressure rotates
Counter-clockwise and parallel to the isobars
Below 2000 feet
Converges approximately 30 degrees from the center
Surface Friction
Reduces wind speed
All fronts are?
All fronts are low pressures.
What is the standard MSL pressure in inches of mercury and millibars?
29.92 Hg and 1013.2 hP/mb
What is an isobar?
A line connecting points of equal pressure (spaced 4 mb apart)
What is the significance of widely spaced isobars on a weather chart?
Widely spaced isobars indicate a weak or flat pressure gradient force and would produce light or calm wind near those locations.
The wind aloft or gradient wind circulation around a high-pressure area is
Clockwise and parallel to the isobars
The wind aloft (gradient wind) direction in the southeast quadrant of a low-pressure area will be approximately from the____?
southwest
Surface wind that converges to the center is associated with____pressure areas, and surface wind that diverges from the center is associated with ____pressure
low, high
What causes the surface wind to flow across the isobars, rather than remain parallel to the isobars?
surface friction
True or False
While flying parallel to the isobars above 2000 feet AGL, the wind is approximately a head wind or a tail wind and the pressure remains relatively constant.
true
If you are flying directly toward a low pressure area, the crosswind will be from your ____?
left
You are flying a course of 045° with steady crosswind from 135°. Based upon the wind direction, what kind of pressure and general weather conditions would you expect ahead?
High pressure area with clear skies and weak pressure gradient force.
Flying on an easterly heading, you observe the aircraft drifting to the right. If you do not reset your altimeter as the flight progresses, you can expect the aircraft to be _____ than the indicated altitude.
lower
Strong pressure gradient force is usually associated with _____ pressure areas.
low
3000’ AGL is from 150°. From which direction is the wind blowing on the surface?
120°
