Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!

Geography

Weather systems

To get a complete picture of the weather, observations are taken and plotted onto a synoptic chart. Watch this video to find out more.

Video

In order to see this content you need to have both Javascript enabled and Flash installed. Visit BBC Webwise for full instructions

Key points

  • A synoptic chart summarises atmospheric conditions such as temperature, precipitation and wind speed.
  • Weather maps use internationally agreed standards and symbols.
  • Isobars are lines on a weather map that join-up places of equal atmospheric pressure. The closer together isobars are, the windier it is.
  • Air masses are large bodies of air, sharing similar temperature, moisture and atmospheric pressure. Fronts occur where two different air masses meet.
  • Warm fronts happen where warm air rises over a mass of cold air. The warm air cools and expands and clouds form.
  • A cold front is the transition zone where a cold air mass replaces a warm one. The cold gradually moves beneath the warm air. It will rain heavily as the warm air is pushed upwards.
  • Occluded fronts happen at the point where a cold front overtakes a warm front or vice versa. Occluded fronts bring changeable weather.
  • Depressions are areas of low atmospheric pressure, which produce cloudy, rainy and windy weather.
  • Anticyclones are the opposite of depressions. They are areas of high atmospheric pressure where the air is sinking.

All Geography videos

Weather and climate index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.