![]() The descriptions given apply to active well developed fronts, weaker fronts may not display all the characteristics or they may be less well defined. The notes below provide information about the most common types of fronts. Fronts move with the wind so over the UK they normally move from west to east. Then you can complete Extension 1 or worksheet 2.Īnticyclones, Depressions and Fronts Part B – FrontsĪ front is a boundary between two different types of air masses, these are normally warm moist air masses from the tropics and cooler drier air masses from polar regions. Using this information on pressure systems you should now be able to complete worksheet 1. Isobars are normally closely spaced around a depressions leading to strong winds.ĭepressions can be identified on weather charts as an area of closely spaced isobars, often in a roughly circular shape, where pressure is lower than surrounding areas. In the Northern Hemisphere winds blow in anticlockwise direction around a depression. This rising air cools and condenses and helps encourage cloud formation, so the weather is often cloudy and wet. Under a depression air is rising, forming an area of low pressure at the surface. Low pressure systemsĪ low pressure system, also known as a depression occurs when the weather is dominated by unstable conditions. An anticyclone situated over the UK or near continent usually brings warm, fine weather. The weather is normally dry, although occasionally, very hot temperatures can trigger thunderstorms. In summer the clear settled conditions associated with anticyclones can bring long sunny days and warm temperatures. If high pressure becomes established over Northern Europe during winter this can bring a spell of cold easterly winds to the UK. Light winds along with falling temperatures can encourage fog to form this can linger well into the following morning and be slow to clear. The clear skies allow heat to be lost from the surface of the earth by radiation, allowing temperatures to fall steadily overnight, leading to air or ground frosts. In winter the clear, settled conditions and light winds associated with anticyclones can lead to frost and fog. As isobars are normally widely spaced around an anticyclone, winds are often quite light.Īnticyclones can be identified on weather charts as an often large area of widely spaced isobars, where pressure is higher than surrounding areas. In the Northern Hemisphere winds blow in a clockwise direction around an anticyclone. Because of these stable conditions, cloud formation is inhibited, so the weather is usually settled with only small amounts of cloud cover. ![]() Under an anticyclone air is descending, forming an area of higher pressure at the surface. ![]() Anticyclones, Depressions and Fronts Part A – Anticyclones and Depressions High pressure systemsĪ high pressure system, also known as an anticyclone occurs when the weather is dominated by stable conditions. ![]()
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