My take on the wind legend:
Each arrow represents wind direction - N, NE, E, SE, S, SW, W, NW
Each layer is at the following altitudes - 14k, 16k, 18k, 20k, 22k, 24k, 26k, 28k
There are actually seven more layers below 14k but typically the wind speed at each of those layers is 0.
The wind speed for each layer from 14k-28k is 20 or 30 knots.
So, at 14k-15.9k the wind is out of the North at 20 knots.
At 22k-23.9k the wind is out of the NorthWest at 30 knots.
My only issue with this is that each layer does not ever replicate.and the winds appear to corkscrew up at 90' (except for the jump from 20-22k which is 120') :S,E,N,W,SE,NE,NW,SW
As far as I know, this pattern is set for the MA no matter the map.