However, there are three such spacings that are by far the most commonly used. Those three show an isobar for every 1, 2, or 4 millibars.

So isobar maps are important for the general public. You know, if you want to look at a weather map, you’ll see those black lines, that they often have between the Hs and the Ls. That’s high pressure ...

I understand isobars are lines of equal pressure but I've never heard anyone mention what the difference in pressure is from one line to the next, is there a standard that everyone uses?