Isobars

 

Isobars are lines drawn on a map to demonstrate atmospheric pressure. The closer the isobars are to each other, the stronger the wind pressure will be. Isobars will also never touch or cross each other. 

http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Hurr_Structure_Energetics/Closed_Isobars/Closed_Isobars.html