weather [appearing pictures with notes] [2]

• Let's recap what we have covered in weather [1]............
  The Sun is the source of the energy that creates wind. Energy from the Sun is unevenly spread across the Earth. Energy in the form of heat causes water droplets in the air to form clouds. Warm clouds of air rise pulling in cooler surrounding air. This creates a cycle of rising warm air [low pressure] and falling cooler air [high pressure]. Low pressure rotates anticlockwise and high pressure rotates clockwise. A barometer measures air pressure and suggests the likely weather. Air pressure systems or air masses can be huge in size.
• Air masses are bodies of air. Here is a cold air mass and a warm air mass over Australia.
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• In the UK we are influenced by cold northern air masses.........
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• .......and two warm southern air masses.. This is why our weather is so mixed.
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• The lines on this UK map are called isobars. They mark areas of same air pressure.
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• Here you can see them without the map. A high pressure area and a low pressure area.
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• High pressure areas move towards low pressure areas which causes a weather front.
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• A weather front is where warmer air and cooler air meet.
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• The weather front is marked where the two air pressure systems meet, in blue and red.
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• This animation shows a front moving across the USA causing rainfall behind it.
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• There are four different types of weather front, the first is a cold front.
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• This is what it looks like on a weather map, a line with blue triangles.
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• The second is a warm front.
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• This is what it looks like on a weather map, a line with red semicircles [mass] not ass.
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• The third is an occluded front.
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• This is what it looks like on a weather map, a line with blue triangles and semicircles.
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• The fourth is a stationary front.
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• This is what it looks like on a weather map, a line with blue triangles and red semicircles.
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• Weather fronts are the boundaries between high and low pressure areas.
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• This animation shows the movement of a warm front across the southern half of the UK.
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• Let's recap what we have covered............
  Air masses are huge bodies of air. We in the UK are influenced by cold air masses from the north... ...and two warm air masses from the south. Lines on weather maps are called isobars. Isobars connect areas of similar air pressure. High pressure areas move towards low pressure areas. Where they meet forms a weather front. There are four different types of weather fronts. A cold front, a warm front, an occluded front and a stationary front. Each have a different symbol on a weather map.

Read each of the labels in turn. As you hover over each of the labels a picture will appear to help you better understand what the label is saying and explaining what the words in bold mean.