FAA Part 107 Remote Pilot (UAG)WeatherHard
A surface analysis chart shows isobar lines packed very close together over the planned operating area. What does this pattern indicate for the remote pilot?
- AThe isobars indicate calm, stagnant air with negligible wind
- BA strong pressure gradient exists, meaning strong winds should be expected
- CWidely spaced isobars like these indicate a strong pressure gradient
- DIsobar spacing has no relationship to expected wind speed
Show answer & explanationAnswer & explanation
Correct answer: B. A strong pressure gradient exists, meaning strong winds should be expected
Isobars are lines connecting points of equal atmospheric pressure. When isobars are spaced closely together, it indicates a steep (strong) pressure gradient over a short distance, which drives faster air movement — i.e., stronger winds. Widely spaced isobars indicate a weak gradient and lighter winds.
Why the other options are wrong
- A. Close isobars indicate the opposite of calm air; they indicate strong wind potential.
- C. This reverses the relationship; wide spacing indicates a weak, not strong, gradient.
- D. Isobar spacing is directly tied to wind speed through the pressure gradient force.
Pressure Gradient and Wind
The pressure gradient is the rate of pressure change over distance; a steeper gradient (closely spaced isobars) produces stronger winds.
- Closely spaced isobars = strong gradient = strong winds
- Widely spaced isobars = weak gradient = light winds
- Wind flows roughly parallel to isobars due to Coriolis effect
Memory trick: 'Tight lines, tough winds' — closely packed isobars mean strong wind.