Approximately how many knots does the wind need to be before whitecaps start to form on waves?

Whitecaps typically begin to form on waves when the wind reaches a sustained speed of around 15 knots. At this wind speed, the energy being transferred from the wind to the water is sufficient to disturb the surface and create white frothy areas known as whitecaps. This occurs as the wave crests become unstable and break due to the strength of the wind pushing against them.

In terms of meteorological phenomena, wind speeds below this threshold do not generate enough force to create significant turbulence at the surface, which is why whitecaps are not seen. Therefore, 15 knots is often recognized as the minimum speed required to witness this visual sign of wave agitation and wind interaction.