Weather Changes 4.8A Background

​Weather




4.8A Measure, record, and predict changes in weather.

Key Concept 1: Tools such as rain gauges, wind socks, and thermometers can be used to gather weather data.

The amount of rainfall is measured by a rain gauge, read in hundredths of an inch. The water level is read at the bottom of the meniscus (curved surface of water in a tube). Most rain gauges have numbers divided into tenths of inches. If the rain gauge is filled to the 0.50 line, that means that 0.5 of one inch, or one-half inch, of rain has fallen. Larger lines mark inches, so if the meniscus reads 0.50 above the 1-inch line, then one and a half inches of rain has fallen.

Key Concept 1:

Wind is blowing air. It is created when there is a difference in air pressures in an area. Hot air rises. Cool air is heavier and sinks. An area of high air pressure is caused by a large amount of cool air. An area of low air pressure is the result of a lot of hot air. Air moves from high pressure (cool air) to low pressure (hot air).

This movement of air is what we know as wind. The speed of wind is determined by how great the difference is in temperature between the two areas of air pressure. Earth's spin also causes air masses to move from west to east in the United States.

Key Concept 1:

Wind socks indicate wind direction and relative wind speed. If the wind sock is limp, there is no wind; however, if the wind sock is blown straight out, then the wind is strong. Meteorologists use anemometers made of spinning cups that accurately record wind speed. A weather vane shows the direction from which the wind blows.

Temperature is measured by Celsius and Fahrenheit thermometers. Although Celsius temperature is used in the laboratory, traditionally Fahrenheit temperature is reported on weather maps in the United States.

Key Concept 1:

Wind is blowing air. It is created when there is a difference in air pressures in an area. Hot air rises. Cool air is heavier and sinks. An area of high air pressure is caused by a large amount of cool air. An area of low air pressure is the result of a lot of hot air. Air moves from high pressure (cool air) to low pressure (hot air). This movement of air is what we know as wind. The speed of wind is determined by how great the difference is in temperature between the two areas of air pressure. Earth's spin also causes air masses to move from west to east in the United States.

​Key Concept 1:

Key Concept 2: We are able to record changes in weather.

We record weather data and are able to see the changes that happen with the weather. We use weather tools like a thermometer, a wind sock, and a rain gauge in order to collect the data that we record. It is important to record changes in weather and weather data because it allows us to predict what will happen in the future.

​Key Concept 3: We use recorded weather information to make predictions.

Meteorologists study the data from weather instruments to make decisions about the upcoming weather. Predicting weather is not an exact science, but some generalizations can help students estimate future weather. Weather generally moves from west to east so conditions to the west will likely move into Texas.

For example, if Phoenix, Arizona, to the west experiences heavy rains, then parts of Texas are likely to receive that weather the next day as the weather moves to the east. It is a rule that high-pressure, good-weather areas move into low-pressure, bad-weather areas. Cloud cover also helps to identify incoming weather:
cumulonimbus clouds indicate a cold front is coming and thunderstorms will soon follow; cirrus clouds followed by nimbostratus clouds indicate a warm front is coming and light rain and drizzle will be around for a couple of days. As soon as a cold front or warm front moves on, bad weather is pushed away by a high-pressure air mass that brings good weather. With modern radar instruments, meteorologists can be more precise at predicting weather, but that prediction is never a guarantee.