That 6 mph forecast is the model output for a grid point, maybe tweaked a little by a human, but it is based on large scale weather events and big terrestrial features like mountain ranges or large bodies of water.
The wind direction and speed a cyclist sees bears only the most general relation to the nominal forecast or what any particular terrestrial station is reporting. Terrain routinely causes right-angle bends in wind flow and vortices that can reverse it 180°. Wind tends to blow straight down tree or house-lined roads, regardless of overall pressure gradient direction. Pressure gradients compress and intensify along ridges or rows of buildings when direction is parallel and the same features serve as windbreaks when the direction is perpendicular. Racing sailors see these effects every time they round a point, sail under a bluff, or enter a river. It’s just way more intense and complex on land.