That would be Force 7 on the Beaufort scale, so just below Gale Force 8.
Each full feather represents 2 and a half feather represents 1.

The feathers do not represent Beaufort Forces but units of 5 kn, but by
a happy coincidence it amounts to the same thing for Force 8 (just) and Forces
9 and 10. 50 kn is Force 10 all right but 15 kn is Force 4, not 3.

Tudor Hughes, Warlingham, Surrey.