The circular lines you see on the chart are isobars, which join areas of the same barometric pressure. The pressure pattern is important because we can use it to tell us where the … See more

Also on a synoptic chart are the lines, triangles and semi-circles representing 'fronts'. With the atmosphere trying to balance temperature, pressure and wind there are di… See more

A warm front is shown with a red line and red semi-circles and a cold front with a blue line and blue triangles. The way in which the semi-circles or triangles point shows the direction in … See more

Cold fronts tend to move faster than warm fronts and over time they can catch up with each other and create an 'occluded' front. This is shown as a purple line with a purple semi-circle … See more