Check the Intellicast map of the U.S. to see the range of values for today. Winds will blow from areas of high pressure to areas of low pressure. The pressure gradient is the magnitude of the change in pressure between two points divided by the distance between those points. The greater the contrast in pressure and the shorter the distance, the steeper the gradient will be and the faster the wind will blow. Isobars, lines of constant air pressure, connect points of equal pressure.
Arrows indicate wind direction, from high to low pressure regions.
Wind direction is initially controlled by the pressure gradient, flowing perpendicular to the isobars and parallel to the maximum pressure gradient. However, that initial wind direction will be modified by the influence of the Coriolis effect and friction close to the planet's surface. The Coriolis effect will deflect winds blowing from areas of high pressure. Winds will continue to be deflected until the pressure gradient effect balances the Coriolis effect and the wind moves parallel to the isobars. Winds blowing parallel to isobars are termed geostrophic winds .