FAA Aircraft Dispatcher (ADX)MeteorologyMedium
A dispatcher comparing two surface analysis charts notices that isobars over the planned route are spaced much closer together on today's chart compared to yesterday's, with no change in latitude. What does this closer spacing indicate?
- AA stronger pressure gradient and stronger surface winds
- BAn area of stable air with no vertical motion expected
- CA weaker pressure gradient and lighter surface winds
- DAn occluded frontal boundary is beginning to form
Show answer & explanationAnswer & explanation
Correct answer: A. A stronger pressure gradient and stronger surface winds
Isobar spacing directly reflects the pressure gradient force: closely spaced isobars indicate a steep pressure gradient over a short distance, which produces stronger geostrophic and surface winds. Widely spaced isobars indicate a weak gradient and lighter winds.
Why the other options are wrong
- B. Isobar spacing relates to wind speed, not vertical stability.
- C. This describes widely spaced isobars, the opposite of the scenario.
- D. Occlusion is a frontal process, not indicated by isobar spacing alone.
Pressure Gradient Force
The force that drives wind from high to low pressure, proportional to the rate of pressure change over distance shown by isobar spacing.
- Close isobars = strong gradient = strong wind
- Wide isobars = weak gradient = light wind
- Wind speed is proportional to gradient, not pressure value itself
Memory trick: Tight lines, tight winds — squeeze the isobars, squeeze out speed.