New to synoptic charts?
- Isobars (curved lines with numbers)
- Lines of equal pressure in millibars. Close together = strong wind. Wide apart = light wind.
- Low pressure (L)
- Unsettled weather — cloud, rain, stronger winds. Air spirals anticlockwise into the centre.
- High pressure (H)
- Settled weather — light winds, clearer skies, often dry. Air spirals clockwise outward.
- Cold fronts (line with blue triangles)
- A wedge of cold air pushing under warm air. Expect a sharp band of rain or showers, then colder, clearer air behind it.
- Warm fronts (line with red semicircles)
- Warm air riding up over cooler air. Prolonged rain ahead of the front, then milder, murky conditions after it passes.
- Occluded fronts (line with both triangles and semicircles)
- A cold front catching up with a warm front. Usually means persistent rain and cloud.
For hill walkers: tightly-packed isobars near your area mean strong summit winds. Fronts crossing your area mean rain. A large high pressure system sitting over the UK usually means a good day on the hills.
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Charts updated twice daily by the Met Office. Images via Wetterzentrale.
Charts: Met Office surface pressure analysis. Crown Copyright. Hosted by Wetterzentrale.