Looking at the BBC weather forecasts I've often noticed that strong winds will often be over 40 knots (for the UK at least). Most of the time (nearly always) the wind will jump from 18-22 knots to over 40 from one hour's forecast to the next. I don't often ever see wind speeds in the high 20s or 30s. Why is this the case? I looked at the Weibull distribution but this doesn't seem to apply.
This is an (annoying) artefact of BBC weather forecasts, and not an actual feature of the weather.
At low wind speeds, the speed shown is the expected average speed.
At higher wind speeds, the speed shown is the maximum expected gust.
It changes over when the maximum expected gust is 40 mph (not knots). You can tell the difference because average wind speeds have a white background, and gusts have a black background:
There is a little bit of explanation about half way down this page: https://www.bbc.com/weather/about/17185651