ghs depression

•Synoptic chart are more detailed weather map used by meterologists (weather forecasters).

•The main weather element shown on a synoptic chart is air pressure. Isobar lines, which join up areas of equal air pressure, are drawn on these maps.

•The closer together the isobar lines are then the windier it is.

•The pattern these lines show areas of low pressure or high pressure. You will be expected to recognise several features on these maps including isobars, low pressure systems (and the associated fronts)

•You will also need to state the type of weather associated with these synoptic charts.

Synoptic Charts and Weather Forecasting

Depressions

•A depression is an area of low pressure.Depressions form when cold air meets warm air and this brings changeable weather.

•A depression is shown on a synoptic chart by a warm front (the front of a warm air mass) and by a cold front (the front of a cold air mass). When the cold air catches up with the warm air this is shown as an occluded front.

•All three fronts are associated with rain

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1. What are the lines of equal air pressure called?

3.Draw the symbols for: i) a cold front ii) a warm front

4. What happens at cold and warm fronts?

A Synoptic Chart

2. How can we tell this chart shows a depression?

5. How can we tell from the isobars that it is moderately windy?



The warm front is called the leading front as it is first to passover places in the UK.

The warm front marks where a mass of warm meets a mass of cold air.

At this front warm air rises over the mass of cold air. As the air rises the air cools, condenses, forms clouds and produces rain.

The passing of the warm front



As the warm front passes over the rain will stop and it will become drier.

Places in the UK will now be in the warm air sector between thefronts and temperatures should be warmer as a result.

The cold front will be next to pass over and this will again bringrain.



At the cold front the warm air is forced to rise above the coldair mass coming along.

Again warm rising air cools, condenses, forms clouds and will give rain.

Passing of the cold front



In the northern hemisphere winds in a depression blow anticlockwise around the depression and (roughly) parallel the isobars

6. What causes it to rain along the cold front?

7. Why does it become warmer after the warm front passes over a place?

8. Describe what happens to the next to the weather as the cold front moves in.

9. In what direction do winds blow around a depression in the UK?



G

10. Describe the weather in Glasgow (G).

11. Describe and explain how the weather in Glasgow will change later in the day.

A point toremember is that depressionsmove across the UK in a generally West to EastDirection.

ghs depression

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