Surface winds are often dominated by high or low pressure systems that typically move from west to east across the United States. In the Northern Hemisphere, these winds flow counter clockwise and inward toward the center of a Low Pressure System and clockwise and outward from a high pressure system as indicated by the arrows depicting wind speed and direction in the below NOAA charts (go to http://aviationweather.gov for current charts). Also you can see in the NOAA charts that the surface winds generally move in the direction from a high pressure system to a low pressure system. The greater the pressure gradient (closer the constant pressure lines are together on the chart) of a high or low pressure system the greater the wind speed as indicated by the number and size of “barbs” on the wind speed arrows. The large barbs indicate 10 knots (multiply knots by 1.15 to get MPH) of wind speed and smaller barbs 5 knots of wind speed and are added together to get total wind speed. For example: two large barbs and one small barb indicate 25 knots of wind. Think of the barbs as feathers on an arrow that points in the direction of the wind.
Point to Ponder: Why don’t these charts show differences in wind speed and direction that should occur as a result of terrain variations like mountains and bodies of water interfering with synoptic winds created by large area atmospheric pressure differences?