High pressure systems create clear, sunny weather as sinking air warms up, reducing condensation. Low pressure systems produce cloudy, rainy weather as rising air cools, allowing water vapor to condense into clouds. When warm and cold air meet, the denser cold air pushes under the less dense warm air, forcing it to rise and cool, creating clouds and potentially rain or snow if the air cools enough. As a depression passes overhead, it brings first a cold front with rain, then a warm sector with some showers, and finally a warm front with more widespread rain.

1. Air Pressure and Weather
What different kinds of weather do
high and low pressure create?

2. Different kinds of Air Pressure
What’s the difference between high and low pressure?
Air that is sinking
Air is pressing down
onto the surface of
the earth.
Air that is rising
Air is lifting off and
moving away from the
surface of the earth.

3. Different kinds of Air Pressure
What would happen to this air?
Warm air
Cold air
Molecules far apart.
Molecules close together.
Molecules moving
around a lot.
Molecules not moving
around much.
Less dense.
More dense.

4. Weather under High pressure
What kind of weather does high pressure create?
As the air sinks it warms up and so
there is less chance of condensation.

5. Weather under High pressure
What kind of weather does high pressure create?

6. Weather under Low pressure
What kind of weather does low pressure create?
As the air cools, water in it
condenses forming clouds.
As it rises the
air cools.
Warm air rises.

7. Weather under Low pressure
What kind of weather does low pressure create?

8. Weather under Low pressure
What happens when warm and cold air meet?
The warm air rises
over the cold air and
cools down.
The cold air is
more dense
The warm air is
less dense
Cold air
Cold air
Warm air
Warm air
This is a front

9. Weather under Low pressure
What kind of weather does low pressure create?
Warm air rises
over colder/cool
air because it
less dense.
As the warm air
rises is cools.
As the air cools,
water in it
condenses
forming clouds.

10. Weather under Low pressure
What kind of weather does low pressure create?
Cold air pushes
under warm air
because it is
more dense.
The less dense
warm air is
pushed upwards
and as it rises it
cools.
As the air cools,
water in it
condenses
forming clouds.

11. Weather under Low pressure
How does weather in a depression change?
Cold Front
Cold air forces
the warm air up
producing cloud
and rain.
Warm Sector
The temperature
rises, its cloudy with
a few showers but
no heavy rain.
Warm Front
Warm air rises
over cold air,
producing cloud
and rain.