Weather Report

Predicting the Weather

Open Ended

What is the primary source of energy that drives the weather on Earth?

The sun is the primary source of energy that drives weather on Earth.

The weather in an area also depends on atmospheric conditions, movement of air masses, and geography.

Open Ended

RECALL: What direction do weather patterns travel across the United States?

In the United States, weather patterns typically move from west to east.

Open Ended

Based on yesterday's lesson, what do you think the symbols "H" and "L" stand for on a weather model?

• A local area of air that is at a higher pressure than the air masses around it

• Usually are made of cooler air

• Air will spread out, or diverge.

​​High Pressure System

• A local area of air that is at a lower pressure than air masses around it.

• Usually are made of warmer air

• Often at the center of severe weather

​​Low Pressure System

A warm front is a "boundary" that is created when a warm air mass moves in to meet an area of cold air.

Warm Front

​A cold front is a "boundary" that is created when a cold air mass moves in to meet an area of warm air.

​​Cold Front

​A stationary front occurs when a warm air mass has met a cold air mass and both air masses are at a standstill.

​​Stationary Front

A trough is an elongated area of low pressure.

​​Trough

• An occluded front occurs where a faster-moving cold air front is overtaking a warm air front.

• The air from the cold air mass is coming into contact with cooler air that was ahead of the warm front.

• Since the air in the cold front can be either cooler or warmer than the cool air in front of the warm air mass, many different kinds of weather can occur.

• Changes in wind or temperature may take place, and either steady rain or storms may form.

​​Occluded Front

Multiple Choice

A weather front occurs when two air masses of differing temperatures meet. When a cold air mass meets a warm air mass, for example, what will happen to the warm air?

• It will rise.

• It will sink.

• It will reverse directions.

• Nothing will happen.

• When a cold air mass meets a warm air mass, the warm air will rise above the cold air.

• This occurs because the air particles move faster and are located farther apart from each other in a warm air mass than in a cold air mass.

• The farther distance accounts for the warm air's lower density and ability to rise above the cold air.

Multiple Choice

A cold air mass and a warm air mass are predicted to meet. What type of weather can be expected between the two air masses?

• dry weather

• stormy weather

• cold weather

• warm weather

• The movement of air masses can be clues to future weather conditions.

• When two air masses meet, the boundary between them is called a front.

• The cold air pushes the lighter warm air upward.

  • This is called frontal lifting, and causes condensation and possible precipitation in the area of the front.

Multiple Choice

To prepare for the first day of school, Jeremy watches the weather forecast on television. The weather map he sees is shown.

If Jeremy lives at point _______, he can expect mild weather conditions for his first day of school.

• Y

• W

• Z

• X

​The weather map shows several different regions that are forecast to experience several weather types.

- Point X lies in the high pressure system, which will create fair weather conditions.

- Point W lies in the low pressure system which produces clouds and rain,

- Point Y lies under the influence of warm front where showers are expected, and

- Point Z lies close to the cold front which would experience rain or storms.

Multiple Choice

Fey measures wind speed every fifteen minutes for one hour in her back yard. Her data is recorded in the table.

As Fey takes her last two measurements she notices that the temperature drops suddenly. Which of the following weather predictions would be best for Fey to make?

• A hail storm is approaching.

• The air's humidity is decreasing.

• A tsunami is approaching.

• A cold front is moving in.

Fey could predict that a cold front is moving in. An advancing cold front is often associated with increasing surface wind speeds and falling temperatures. Very often, such fast-moving cold fronts result in precipitation. So Fey might also be able to guess that it will soon rain.