Download Weather Definitions

Weather Terms Low pressure systems are giant funnels of wind moving inwards and upwards, causing warm air to rise thus cool and then clouds are formed. So, low pressure causes overcast weather and precipitation. The wind direction is anticlockwise about the centre (in the Northern Hemisphere) and the systems normally come from the Atlantic. High pressure systems, on the other hand, are associated with more dry and cool weather. Winds move clockwise about the centre in the Northern Hemisphere. High pressure also brings clearer skies, so there will be no reflection of warm air from clouds, thus the nights will be chilly. A cold front is when a cold air mass moves into a relatively warmer air mass. It is represented as a blue line with triangles on weather maps. A cold front obviously brings cooler conditions, but also brings drier weather. The pressure begins to steadily increase once the front has passed. As the front is passing, the weather is often windy and there is heavy rain. A warm front is almost opposite to a cold front in a lot of ways. It is formed when a warm air mass is moving into a cooler air mass. The air is more humid and warm once the front has passed. The clouds become higher in the sky as warm air rises. There is little rain or wind as the front passes and is represented as a red line with semicircles. An occluded front happens when a cold front catches up with a warm front. The air is colder behind the front, but is cool ahead of it. It is represented by a purple line with alternating triangles and semicircles.