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A line joining points of equal air pressure on a weather chart.
Also known as: Pressure line, Lines on a weather map
Isobars join points of equal pressure. Their spacing gives the wind: tightly packed isobars mean strong wind, which is why a forecaster can read wind speed off a pressure chart without any wind being drawn on it.
Joins points of equal atmospheric pressure, reduced to sea level so that places at different altitudes can be compared.
Contexts: Navigation
Conveys wind strength by spacing: closely spaced isobars mean a steep pressure gradient and strong wind.
Contexts: Navigation
Encloses centres marked H and L, which are simply the highest and lowest pressures of their neighbourhood rather than fixed thresholds.
Contexts: Navigation
A smooth closed or open curve labelled with a pressure value, running across the chart and nesting with neighbouring curves without touching them.
The same construction applied to pressure instead of height.