A remote pilot is preparing for a construction documentation mission. The nearest weather station reads 9 knots of surface wind. Observing the tree line along the property, the pilot notices upper branches swaying vigorously while lower foliage is relatively still. What is the most accurate interpretation?

Question

Accepted Answer

Wind speed likely increases significantly with altitude due to wind gradient: conditions at 200–400 feet AGL may be considerably stronger than the surface reading suggests.. Wind gradient describes the phenomenon where wind speed increases with altitude as surface friction from terrain, buildings, and vegetation slows the wind near the ground. Vigorous upper branch movement with calm lower foliage is a visual indicator that wind speeds aloft are substantially higher than the surface measurement. At 200–400 feet AGL, actual wind may be 1.5–2.5 times the surface reading.

Answer

Surface wind readings are more reliable than visual observation: the 9-knot reading is the operative data.

Answer

Vigorous treetop movement indicates gusting only, not sustained wind: the drone should be unaffected during steady flight segments.