Wind barb

Wind Barbs are symbols used on weather maps [http://polar.ncep.noaa.gov/waves/latest_run/wna_ecg.anim.gif] to indicate the speed and direction of wind.

A barb is comprised of a minimum of two straight lines, the longest of which indicates the wind direction. Additional lines indicating wind speed begin at the tail of the wind direction line and extend out at slight angles. Though not required, arrow heads on wind barbs are typically square when present, and point the direction that the wind is blowing toward. The basic barb unit is equal to 10 knots, and half a barb is equal to 5 knots. The barbs are stacked in combination to display windspeeds of up to 45 knots. A wind speed of 50 knots is then indicated with a triangle. As wind speeds begin to increase above 50 knots barb lines are again stacked over the triangle to indicate 5 and 10 knot graduations.