Applications

See also: Surface weather analysis and Weather forecasting

Digital graphing barometer.

Barograph using five stacked aneroid barometer cells.

Using barometric pressure and the pressure tendency (the change of pressure over time) has been used in weather forecasting since the late 19th century.^[17] When used in combination with wind observations, reasonably accurate short-term forecasts can be made.^[18] Simultaneous barometric readings from across a network of weather stations allow maps of air pressure to be produced, which were the first form of the modern weather map when created in the 19th century. Isobars, lines of equal pressure, when drawn on such a map, gives a contour map showing areas of high and low pressure.^[19] Localized high atmospheric pressure acts as a barrier to approaching weather systems, diverting their course. Atmospheric lift caused by low-level wind convergence into the surface low brings clouds and potentially precipitation.^[20] The larger the change in pressure, especially if more than 3.5 hPa, the larger the change in weather can be expected. If the pressure drop is rapid, a low pressure system is approaching, and there is a greater chance of rain . Rapid pressure rises, such as in the wake of a cold front, are associated with improving weather conditions, such as clearing skies.^[21]