Isobar

http://www.srh.noaa.gov/ffc/?n=mapslast

Isobars look at air pressures in a region.  It connects areas that have equal atmospheric pressure over a period of time. This is used on weather maps and the lines on them may never touch.  Typically, these pressure lines are usually connected to sea level and are generated to make it easier to establish where high and low pressure zones are located.