Meteorology and Weather Forecasting

Jonathan BlaesNational Weather Service

Raleigh, NC

What Is Weather?

“Weather” refers to the conditions of the atmosphere at a certain place and time.

Meteorology is the science of the atmosphere. It takes its name from the Greek word meteoron-something that happens high in the sky.

We Can’t See Air, So What Can We Measure?

• Temperature• Pressure• Wind direction and speed• Moisture—humidity and dew point• Precipitation—type and amount• Clouds—coverage and type

Temperature

• Temperature is a measure of how much heat energy the air molecules possess

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Pressure• Air molecules push down on

objects—including you—with a force that we call the “barometric pressure.”

Wind Direction and Speed

• When air moves—”wind”—we feel both its direction and speed (force.)

• Direction is measured with a “vane”—an arrow or other shape that points into the wind.

• Speed is measured with an “anemometer.” The faster the cups spin, the faster the wind.

Measuring Precipitation

• Rain is easy to measure—all you need is an “open tube with a ruler”—a RAIN GAUGE.

What are clouds?

A cloud is made up of tiny water droplets and/or ice crystals floating in the atmosphere.

The Water Cycle

Cloud Formation

Clouds form when solar heating of the earth’s surface warms the air near the ground. This air begins to rise and it expands and cools. Water vapor then condenses on small dust particles suspended in the air and these combine to form clouds.

The presence of clouds in the sky is one type of signal to meteorologists that there will be changes in the weather. Predicting the weather requires the understanding of the different types of clouds.

Cloud Types

CloudsCumulus or fluffy clouds form when air is forced up rapidly and therefore rises higher.

Cumulus

Stratus clouds are layered clouds that form when air that is forced up slowly.

Stratus

Clouds

Cirrus clouds are thin feathery clouds.

Cirrus

Clouds

• High pressure causes air to sink

• Usually results in several days of clear sunny skies

• Air rises in low pressure areas and forms water droplets

• Usually results in rain and storms

High and Low Pressure

Lets Make a Cloud

What we need…1) Moisture2) Decrease in air pressure

Lightning

Lightning

When thunder roars, go indoors!

Questions