This is a computer forecast of sea level pressure in millibars and wind in knots about 30 ft above the ground for tonight at 1 AM EST. The shaft of the wind has a small dot at the end. The wind blows along the shaft toward the dot. The wind barbs which come out at right angles to the shaft show the wind speed. Each full barb is 10 knots, each half barb is 5 knots, each flag is 50 knots. 10 knots equals about 11.5 mph.