Mapping the weather
Meteorologists use the information that they collect to produce synoptic charts and find patterns in the weather that might affect their local area in the future. Synoptic maps show weather information in symbol form.
Air pressure is the weight of the atmosphere over a unit of Earth’s surface. Changes in weather are usually accompanied by changes in air pressure and this is shown on weather charts by isobars. Isobars, the lines on a pressure map, connect points of equal pressure at 4 or 8 millibar intervals.
High pressure is shown by a series of isobars in a circular shape with the highest value in the centre. High pressure is cool air sinking and indicates weather of light winds that is settled or dry.
Low pressure is also shown by a series of isobars in a circular shape with the lowest value in the centre. Low pressure is warm air rising and indicates weather of high winds and rain. The close spacing of isobars indicates strong winds associated with low-pressure systems.