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Isobars, fronts, pressure centres and station circles, in one picture.
Also known as: Weather map, Pressure chart, Lines and symbols on a weather map
A weather map is four notations laid over one another: closed lines of equal pressure, high and low centres, boundaries between air masses, and a plotted observation at each station. Each answers a different question, and reading them in that order is what makes the chart legible.
A chart plotting simultaneous weather observations over an area, carrying isobars, marked pressure centres, front lines and a plotted station model at each reporting point.
Contexts: Maps
Spacing carries the wind. Isobars close together mean a steep pressure gradient and strong wind; widely spaced isobars mean light wind, and this is readable from the chart before any wind symbol is examined.
The word synoptic means seen together: the whole value of the chart is that every observation on it was made at the same moment, which is why national services agree on fixed observation hours.
A map overlaid with closed curved lines, capital letters H and L in their centres, and lines carrying rows of small triangles and semicircles, with small circles scattered across it.
The station model is what is plotted at each point on the chart.