34–40 knots. Moderately high waves of greater length; edges of crests break into spindrift.
Winds are categorized based on their intensity and the observed conditions they cause: gail force
28–33 knots. Sea heaps up and white foam from breaking waves begins to be blown in streaks. 34–40 knots
Gale force winds can cause structural damage to roofing and siding and create life-threatening conditions for mariners. Weather Spotter's Field Guide - Non-supercell Tornadoes gail force
48–55 knots. Very high waves with long overhanging crests; the sea surface takes on a white appearance. Safety and Preparation Guide