Weatherwatch: how frontal systems work

https://www.theguardian.com/news/2019/oct/16/weatherwatch-how-frontal-systems-work

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The British Isles are often at the mercy of the jet stream, which roars across the Atlantic bringing with it, in the form of frontal systems, the country’s often wet and changeable weather.

Frontal systems form due to the clash of opposing warm and cold air masses. The boundary of where the air mass transitions from cold to or warm, and vice versa, is known as either a cold front or a warm front. There are three types of fronts – warm, cold and occluded. As the name suggests, a warm front marks the boundary of an advancing warmer air mass, usually the tropical maritime air that originates from the subtropical Atlantic, while a cold front marks the boundary of a cold air mass. An occluded front is where the cold air mass associated with the cold front catches up with the warm front and the warm air is forced aloft.

In more continental regions of the world, the passage of a frontal system can bring sudden extreme changes. Last week Denver, Colorado, saw temperatures reaching a balmy 27C. Less than 24 hours later, however, following the clearance of a cold front temperatures plummeted to -7C with heavy snowfall.