In this lesson, students will use a database to learn about, organize, and compare tornadoes in their home state and across the country. [Note: This lesson can be conducted in conjunction with the giant screen film, Forces of Nature, either before or after students view the film.]

Geography, earth science

Standard 1: "How to use maps and other geographic representations, tools, and technologies to acquire, process, and report information from a spatial perspective"
Standard 7: "The physical processes that shape the patterns of Earth's surface"
Standard 17: "How to apply geography to interpret the past"
Standard 18: "How to apply geography to interpret the present and plan for the future"

[Note: This lesson also conforms to National Science Education Content Standard F (Science in Personal and Social Perspectives: Natural and human-induced hazards) for grades 9-12.]

Two to three hours

• Computer with Internet access
• Pencils or markers
• Graph paper or computer program for constructing graphs and tables
• Handout (or transparency) of the map, "Annual Average Number of Strong-Violent (F2–F5) Tornadoes, by State, in the U.S., 1950–1995"
• Outline map of counties in your state
• Blank Xpeditions outline maps of the U.S., one for each student

Students will

• apply aspects of tornado science, including the Fujita scale;
• demonstrate skills in searching a database to answer questions; and
• analyze data on charts and maps, comparing tornadoes in their state to those in other states.

[Note: This opening may vary, depending on your community's or state's experiences with tornadoes, and whether or not students have seen the giant screen film, Forces of Nature.]

To set the stage for this lesson, have students review National Geographic: Forces of Nature, take the National Geographic Weather Wizard quiz, or check out an animated Quick Flick about tornadoes.

Ask each student to write a list of "Tornado Knowns and Unknowns"—things they think they know about tornadoes, and things about tornadoes they would like to learn. Students might briefly compare their lists with their neighbors', then as a class share their lists orally or on the board; this will help determine their level of understanding and clarify any questions.

Tell students that they will be working in groups to research and display actual tornado data. To set this up, ask the following questions:

• What factors can contribute to the formation of a tornado?
• Do tornadoes occur in our state? Are they more likely to occur in our state than in others? Where are they likely to occur? When might they occur?
• Why are some tornadoes more destructive than others?
• How do atmospheric scientists study tornadoes? [Note: If students have seen the giant screen film Forces of Nature, methods of tornado chasers like Dr. Josh Wurman might be discussed.]

Tell students that one important way in which scientists classify tornadoes is by estimated force, based upon damage observed. Introduce the Fujita scale, which measures and ranks tornadoes on a scale of F0–F5. [Note: The Fujita scale goes higher—from F6 ("inconceivable" damage) all the way up to F12—but an F5 is the most intense type of tornado that has ever been observed.]

In groups of two to four, have students investigate the searchable Storm Events Database. Ask them to retrieve some of their state's tornado data, then construct charts of the data. Because this database is comprehensive, give students parameters for their search. For example:

• Select your own state.
• Set a "Begin Date" in the past ten years or fewer. (For states with few tornadoes, retrieve data for more years.)
• Use default "End Date" or set a recent date.
• Select "all" counties.
• Select "tornadoes" for "Event Type."
• Search for tornadoes "F2 and Higher." (For states with few tornadoes, students can choose another state where they think more tornadoes might occur, or search for "all" tornadoes in their own state.)
• Click "List Storms."

[Note: If a single tornado occurred in more than one county, the database lists all counties in which it occurred in the "Location or County" column.]

Once groups have retrieved the data, assign each group a different way to organize and analyze their tornado data:

• Create a bar chart of total tornadoes, by year (e.g., all tornadoes in the past ten years).
• Create a bar chart of tornadoes, by Fujita scale ranking.
• Create a bar chart of total tornadoes, by month.
• Create a bar chart of tornadoes by time of day (e.g., by the hour or in blocks of hours).
• Create a bar chart or other graphic to depict casualties, property damage, or other characteristic.
• Create a map showing the county or location of each tornado (by Fujita scale ranking or number of casualties, if appropriate).

As they complete their task, tell each group to analyze their results and write a few descriptive statements about their results. (Example: The most tornadoes in our state, over the time period studied, occurred in 1998. There were fewer F3 than F2 tornadoes. More tornadoes occurred in spring than in other seasons, and more afternoon than morning tornadoes. More tornadoes occurred in the western part of the state.)

These analyses can be shared (as scientists do) via brief group presentations and with summary statements written on the board. Each group's findings will have added to the understanding of the entire group. Explain to students that they have collectively constructed a set of (probable) "Tornado Truths" for their state

Show students the map, "Annual Average Number of Strong-Violent (F2–F5) Tornadoes, by State, in the U.S., 1950–1995." Ask them to consider this map and use the Storm Events Database to answer the following questions:

• How does our state compare to others, tornado-wise?
• Which states have the most tornadoes, on average?
• Does this data mean that each state will have roughly the same number of tornadoes indicated on the map every year (e.g., Texas will have 29 and Colorado will have 2), or are there years of heavy tornado activity which seem to skew the data?
• How would you describe the spatial pattern of tornado events in the U.S.?
• Does Tornado Alley live up to its name, according to this map and the other data you have found?

Retrieve data for a single year of F2–F5 tornadoes in the U.S. from the Storm Events Database. Print out the data for students. Give each student a blank Xpeditions outline map of the U.S. Students should put the data for the single year on the outline map. Ask students to carefully study and compare their map with the map "Annual Average Number of Strong-Violent (F2–F5) Tornadoes, by State, in the U.S., 1950–1995," then write answers to these questions:

• Does the number of tornadoes in this one-year period "fit" the annual average number of tornadoes nationwide? State-by-state?
• Did tornadoes occur in this year in a similar distribution pattern?
• Based upon the patterns displayed in your map, can you predict in which states the highest number of tornadoes might occur in the following year? (Students can check their estimate online in the database.)

Evaluate students' work based on the amount of detail and accuracy in oral and written presentations and on the use of research. Students should show their ability to

• apply the Fujita scale to classify tornadoes;
• use a database to gather information, create bar charts and a map, and to ask and answer questions about tornadoes;
• analyze and compare tornadoes in their state with those in other states; and
• predict tornadic occurrences, based on collected data.

• Ask students to find out why some tornadoes cause more loss of life and damage than others.
  
  
• In the Storm Events Database, have students examine different Event Types (hail, drought, snow and ice, etc.) in their state. Which type of event caused the most property damage (or crop damage, loss of life, or injury) in their state for the most recent year of recorded data? Have students construct tables, charts, or maps of events.
  
  
• The U.S. has more tornadoes annually than any other country. Ask students why that is so. Then ask students to find data and descriptions of tornadoes in other countries or regions. Do these other countries or regions share any similarities with the areas of the U.S. where tornadoes are more likely to occur? Are there different names for tornadoes in other regions?
  
  
• Ask students to research the reasons that their state has few or many tornadoes annually.

Credits:
Map "Annual Average Number of Strong-Violent (F2–F5) Tornadoes, by State, in the U.S., 1950–1995" from the National Climatic Data Center.

National Climatic Data Center: Storm Events Database
National Geographic: Forces of Nature
National Geographic: Tornadoes Quick Flick
National Geographic: Weather Wizard Game
National Severe Storms Laboratory: Tornadoes...Nature's Most Violent Storms
Scholastic: Weather WatchTornadoes
Tornado Project Online
USA Today: Weather ResourcesTornadoes
Why Files: TwisterThe Tornado Story