What is a Cold Front?
http://covis.atmos.uiuc.edu/guide/fronts/cold/def.html
A cold air front is the place where a cold air mass replaces a warm air mass.
These different air masses do not mix because they have different temperatures and densities. As the cold front develops the warm air behind the front is pushed up over the top of the cold air. This happens because the warm air is lighter than the cold air. You often see clouds forming at a cold front. This is because as the warm air rises, it cools and condenses. Clouds are masses of cool condensed air.
The Formation of a Cold Front
http://www.usatoday.com/weather/wcfront.htm
Fronts can be several hundred kilometres in width. The air behind a cold front is cooler than the air in front of it. If a warm front passed overhead when you were standing outside, then you would feel the air cooling down. The air would also be dryer than before.
We are now going to look at a weather map from the Electronic Telegraph web site. This will help us understand how to recognise a cold front.
A Cold Front Over the UK on the 24th December 1997
http://www.telegraph.co.uk |
This chart shows the progression of a cold front
over the UK on the 24th December 1997. The front is the black line with the
triangular lumps on it. It travels in the direction of the wind - in this case west
to east. You can see that the weather conditions ahead of and behind the front are
different.
We said before that the air temperatures ahead of the cold front are usually warmer than the temperature behind the cold front. We can see the difference on this map.
What is the change in air temperature ahead of and behind the cold front?
What other weather conditions change ahead of and behind the front? |
Write down the main differences between a warm and a cold weather front.
Do you think that you would now be able to find a cold front on a map? If you do then look at the map below. If you don't, then carry on with this tutorial.
Quiz
The following map shows two locations where there might be a cold front over the UK. The white numbers are the air temperatures in degrees Celsius. Using the information given above work out which line represents the cold front.
Two Possible Locations For a Cold Front
We can now look at some of the data collected from the ECN sites around the country. This will help you understand the changes in weather as the front passes over.
Alternatively, would you like to look at more information about the ECN?
