Water Cycle - Weather (3)
Post Lab 

  • Comparing different types of weather.
  • Discovering how tornadoes form.
  • tornado
  • troposphere

Students create a tornado.


The troposphere creates conditions that produce all weather including severe storms.  Some areas are more prone to certain conditions than others. For instance hurricanes commonly occur on the east coast of the United States originating in the warm waters south or southeast of Florida. Certain moisture and wind conditions  in the troposphere create different  weather phenomena.

Thunderstorms, generated by temperature imbalances in the atmosphere, are a violent example of convection. The warming of the air near the Earth's surface and/or the cooling of the air above the surface causes instabilities and convective overturning of various layers of hot and cold air.

A severe thunderstorm may spawn a tornado, a violently rotating column of air which descends from a thunderstorm cloud system. On the average, tornadoes move about 30 miles an hour, however, some move very slowly while others speed along at 60 miles an hour or more.

Floods are a natural and inevitable part of life along the rivers of our country. Some floods occur seasonally when winter or spring rains, coupled with melting snows, or torrential rains associated with tropical storms. Drains, small tributaries, and river basins fill with too much water, too quickly and overtop its bank. Other floods are sudden, resulting from heavy localized rainfall. These flash floods are raging torrents which rip through river beds, urban streets, coastal sections and mountains canyons after heavy rains, and sweep everything before them.

Hurricanes are storms that start over tropical waters. The blazing Sun beats down on the ocean waters day after day and the air above this water gets hot. As cold air moves in, it pushes the hot air up until the hot air reaches a cool layer of air. The water vapor condenses very suddenly and becomes a driving rain. Cooler air from the outside moves in, in a whirling motion, like water going down a drain. The center or "eye" of the hurricane is calm, but all around it the winds and rain are swirling.

  1. There are many books and Internet sites on different meteorological conditions where students can get more information. In a book like Tornado Alert, the author weaves information with a story. When having the students read this book, inform them they are going to get asked questions. You may want to give the questions before the class reads the book aloud, so students can take notes of the answer. If you only have one book have certain students read a page in front of the class.
  2. You may want to have the students play with the "Tornado in a Bottle" before or just after you read the book. Donít quite tell them why they are playing. (You will later ask them if this "model" of a tornado is scientifically accurate.)
  3. Ask the following questions to see if students can transfer knowledge from a literature book. You can easily add to the list.
  1. Why does a real tornado "twist?"
    Cold air meets warm air. The warm air is lighter and moves upward rapidly. As the warm air moves upward it spins around. As the warm air rises it spreads out, giving it a "funnel" look.
  2. If you donít live in "tornado alley" should you know how to protect yourself?
    Yes, because you never know when you may be traveling into such an area.
  3. Is the tornado in the bottle the same as a real tornado?
    No, the "twirling" action is caused by a physical circular motion. In a real tornado the motion is caused by warm and cool air. The water temperature in the bottle is the same throughout.
  4. How does a tornado "suck" up houses? [Example of not all questions are answered in one book?]
    This was not answered in the book. The air pressure inside the funnel plunges several hundred millibars lower than the air pressure outside. This creates a "vacuum cleaner" type suction that can tear trees and suck house up in the funnel. When the tornado stops, the items then plumage to the ground.

  [Back to Water Cycle Grid]  [Back to Weather (3)]