Chapter 18 Notes

Weather

Fronts, pressures, clouds

Fronts - leading edge of a moving air mass.

Pressures – areas of sinking or rising air.

Clouds – visible mass of water or ice in the atmosphere.

Cold Fronts

Cold air mass replaces warm air mass.

Large clouds form – – Cumulonimbus (dark gray storm

cloud)

– Nimbostratus (dark gray, thick snow cloud)

Warm Front

Warm air mass replaces a cold air mass.Produces a series of clouds:

– Cirrus (wispy and transparent)– Cirrostratus (white veils)– Cirrocumulus (rolled patches)– Altostratus (gray sheet or layer)– Altocumulus (patches or rolls)– Stratocumulus (lumpy)

Stationary Front

Occurs when air masses stop moving.Noticeable temperature and wind

direction change.

Occluded Front

Occurs in a Low Pressure system.Cold front catches up with a

warm front.

High Pressure

Areas of sinking air that move clockwise – called anticlones.

Clear, nearly cloudless skies.Pushes bad weather away

HH

Low Pressure

Area of rising air in a counter-clockwise direction called cyclones.

Cloudy, sometimes rainy days.

LL

Meteorology

Meteorologists are scientists who study the causes of weather and try to predict it.

They use maps, charts, and computers to analyze weather data and prepare forecasts.

Use radar to track precipitationNational Weather service tracks weather

and issues warnings and watches.

Weather Technology

Weather balloons – carry instruments high into atmosphere to measure temp., pressure, and humidity.

Satellites – in upper atmosphere; measure temp, humidity, wind speed and direction, solar radiation, and give images of clouds and storms.

Weather Technology (con’t)

Weather stations – on surface; measure temp, pressure, humidity, rainfall, and wind speed and direction.

Computers – process gathered info quickly and help forecasters make predictions using calculations.

Weather Maps

The figure below shows what various weather symbols mean.

Reading Weather Maps

This is the type of weather map produced by the National Weather Service. It shows data collected from many weather stations.

Reading Weather Maps

Weather maps in newspapers use symbols to show fronts, high- and low-pressure areas, and precipitation. Color bands indicate different temperature ranges.

Skills activity

Cumulonimbus

Cirrus

Cirrostratus

Cirrocumulus

Altostratus

Altocumulus

Nimbostratus

Stratocumulus