five-and-ten system

The most common system for representing wind speed, to the nearest 5 knots, in symbolic form on synoptic charts.

It consists of drawing the appropriate number of half-barbs, barbs, and pennants from the end of the wind-direction shaft. In this system, a half-barb represents 5 knots, a barb 10 knots, and a pennant 50 knots.