Pressure pattern (synoptic)

A synoptic pressure pattern is the arrangement of high and low pressure systems, ridges, troughs, and fronts shown on a weather chart for one moment, the snapshot from which the navigator reads the wind and weather over an area. The named features are the depression or low, the anticyclone or high, the col between systems, the ridge, and the trough, each with its own wind and weather signature. The isobars give the gradient wind, and the movement of the systems between charts gives the forecast: a deepening low from the west brings a backing then veering wind and a rising sea. Weather routing reads the pattern over the passage to pick a track that avoids the worst of a depression.