Transcript

What's more fun, building sandcastles in the sun?

Or building snowmen on a frosty day?

Both activities depend on the weather, but how can we predict, or forecast what our weather will be like?

Special scientists called meteorologists try to predict, or forecast, the weather using changes in air pressure.

meteorologists

Air Pressure

Although we often don't notice it, the weight of gases in the atmosphere is pushing down on us all the time.

We call this air pressure.

Air that has gas molecules tightly packed together is heavy and at a high pressure.

high pressure

Air with gas molecules spaced further apart is light and at a low pressure.

low pressure

High–pressure areas often have dry and sunny weather.

This is because the heavy air can't easily rise to form rain clouds.

Whereas air can rise easily in areas of low pressure.

As it rises, it cools, which allows the water vapour in air to condense into rainclouds.

So the weather in low–pressure areas is often wet.

When the air pressure in an area changes, so does its weather.

So meteorologists can use the changes to make forecasts.

meteorologists forecast weather
using changes in air pressure

They monitor the weather with special maps.

The maps show when an area is about to experience a change in air pressure.

The bigger the change, the bigger the change in the weather.

big change in air pressure
big change in weather

Whether you're planning to build sandcastles or snowmen.

It's always a good idea to check the weather forecast first.

meteorologist
air pressure
high pressure
low pressure

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