We are often asked this question by users who are utilising the City of London Weather data, but for design rather than for planning permission, and as such, reduce the number of directions for speed and a reduction in cost for earlier stage design exploration.
We have long known that users will see little difference until a full 36 wind direction study is performed, and a user should not be surprised to see little difference if running fewer directions. To make this more commonly known, we have produced the below example.
Summer
Left: 36 Wind Directions, Middle: 16 Wind Directions, 8 Wind Directions
Winter
Left: 36 Wind Directions, Middle: 16 Wind Directions, 8 Wind Directions
From the above visualisation, we can see firstly that increasing the number of directions does change results to a degree. But more importantly, comparing Winter to Summer, there is only a significant difference for the left-hand images, 36 Wind Directions. A keen eye will see differences for all. However, it is much less obvious.