The Atmosphere
Movement in the Atmosphere
Atmospheric Stability
Localised Winds
Clouds
Fronts
Visibility and Fog
Aircraft Icing
Thunderstorms
Altimetry
Weather Reports and Forecasts
Practice Exam

Synoptic Features

Isobars are not always circular around a high or low pressure system and some features are given their own description.

Ridge

When isobars surrounding a high pressure system elongate in one direction it is called a ridge. The ridge is sometimes described as a finger pointing out of the high.

The ridge has the same stable weather as the rest of the high pressure system but the wind will turn sharply across it.

A ridge is an elongated area of a high pressure system with similar weather to an Anticyclone

Trough

Where a finger is formed by isobars surrounding a low pressure system elongating in one direction, it is called a trough.

Weather in a trough is typically unstable, with rain and thunderstorms being common. The wind will turn sharply across a trough.

Col

Where two highs and two lows are interacting, an area of stagnation between then often forms. This is called a Col.

As there are no isobars in a col, we can say the winds will be light. Other than this, the weather in a col can vary and is influenced by the strongest high or low surrounding it.