I noticed that the other day and almost posted it myself, weird isn't it, sort of a basket weave pattern, either due North or due West.
I saw this aswell and thought the same, weird.
What made it more weird was when i hovered over the graph.... All the North wind direction arrows were showing up with wind direction (north/north-east) and all the west direction arrows were showing up with nothing at all. a dash for wind speed, dash for gusts and dash for direction.
Even more weird than a 90 degree wind shift if you ask me