ChatterBank0 min ago
Yes, Hellywelly, you are correct, but only if the isobars have constant spacing, as OldGeezer has shown. Without constant spacing, calm weather could have closely spaced isobars representing one millibar difference, and wild weather could have widely spaced isobars representing fifty millibars difference. That's why all charts should show the scale. Thank you everyone, I need only to find why the Mersey is shown completely silted, and I'll be happy!