What determines how isobars are drawn on weather maps?

Dear Tom,

What determines how isobars are drawn on weather maps?

— Kyle Mann

Dear Kyle,

Hourly weather observations that include sea-level pressure readings are plotted or printed on weather maps that meteorologists can analyze. Isobars are drawn by connecting points having equal sea-level air pressure, using a specified contour interval. Because air pressure decreases at a rate of about 1 inch per thousand feet of elevation, pressure readings recorded at weather stations are standardized to a common level (sea level). This eliminates changes in surface pressure that are the result of elevation differences. By analyzing and contouring sea-level pressure data, a meteorologist can pinpoint the location of high and low pressure systems and track them as they move across a given geographical area. Isobars help the meteorologist locate frontal boundaries because fronts are located in troughs of low pressure.