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