Urban areas can do lots of funny things with wind. You have to understand that the wind is a fluid that flow just like water. If there are channels...like tall building or trees or even open streets...the wind is going to take the channel that offers the least resistance.

Another issue is turbulence. From my kiting experience, I know that laminar flow wind can be disturbed and show that turbulence up to 3 times the height of the object. For instance, if a 30 foot tree has a wind blowing against it, the wind will flow around the tree and not be laminar for at least 90 feet away. That flow will go just about anywhere in the 90 feet. Add up the other secondary turbulences and you can have wind flowing in just about any direction.

Finally, most people don't understand that wind can still affect you considerably even when it's coming from an angle that isn't parallel to your travel. For example, if a wind comes at you from 45 degrees to your left, you will still perceive it as a headwind. Wind can still have a strong component that seems like a head wind up to almost 90 degrees from either direction. When kiting, this works out to a quarter of a sphere in terms of wind that you can still fly in. Some two line kites actually can take advantage of the edge winds and fly at 90 degrees to that wind. It's tricky to fly at that angle but rewarding if you can pull it off and not crash your kite.