If you don't know what wind barbs are, they are a way of representing both the direction and strength of wind on a map. The more barbs on the line the stronger the wind. Large barbs count for 10 knots and small barbs count for 5 knots. The flags you see count for 50 knots. An example of how this looks on a map can be seen on the weather underground site.
You can download the code
(thanks to Chris Barker for the tip on modeling the code after FloatCanvas.Arrow; it turned out to be very similar)