Chapter 10 Lesson 3 "Storms"
Materials:
Objective:
Anticipatory Set:* Show the students this short video clip of static electricity starting a gas tank on fire. Ask the students what they think happened to start the fire. Introduce the idea of static electricity and ask how it relates to the weather?
Teacher Input:* Show the students a picture of a thunderstorm and ask them to name the weather event. Ask the students to guess how many thunderstorms occur on earth each day? (40,000) Where do most of them occur? (most thunderstorms) Why? Explain what cause a thunderstorm using these pictures: ThunderCause1, ThunderCause2, Thunder Cause3.
Explain three features that can be found in a thunderstorm:
# They are tropical, meaning that
they are generated in tropical areas of the ocean near the Equator.
# They are cyclonic, meaning that
their winds swirl around a central eye. Wind direction is counterclockwise (west
to east) in the Northern Hemisphere and clockwise (east to west) in the Southern
Hemisphere (more about this later).
# They are low-pressure systems.
The eye of a hurricane is always a low-pressure area. The lowest barometric
pressures ever recorded have occurred inside hurricanes.
# The winds swirling around the center of the storm have a sustained speed of
at least 74 mph (119 kph / 64 kt). What
do you a call a similar storm in the Indian Ocean or the western Pacific? (Typhoon)
What causes a hurricane? Hurricanes are intense low pressure areas that form over warm ocean waters in the summer and early fall. Their source of energy is water vapor which is evaporated from the ocean surface. Water vapor is the "fuel" for the hurricanes because it releases the "latent heat of condensation" when it condenses to form clouds and rain, warming the surrounding air. (This heat energy was absorbed by the water vapor when it was evaporated from the warm ocean surface, cooling the ocean in the process.) Usually, the heat released in this way in tropical thunderstorms is carried away by wind shear, which blows the top off the thunderstorms. But when there is little wind shear, this heat can build up, causing low pressure to form. The low pressure causes wind to begin to spiral inward toward the center of the low. These winds help to evaporate even more water vapor from the ocean, spiraling inward toward the center, feeding more showers and thunderstorms, and warming the upper atmosphere still more. The showers and thunderstorms where all of this energy is released are usually organized into bands (sometimes called "rain bands" or "feeder bands"), as well as into an "eye wall" encircling the center of the storm. The eye wall is where the strongest winds occur, which encircle the warmest air, in the eye of the hurricane. This warmth in the eye is produced by sinking air, which sinks in response to rising air in the thunderstorms. The winds diminish rapidly moving from the eye wall to the inside of the relatively cloud-free eye, where calm winds can exist.
Guided Practice:* Students will answer the questions from Page 246. Each site will take turns with a question.
Independent Practice:* Students will complete the worksheet, "Storms"
Check for Understanding:* Students will take the quiz for lesson 3, "Storms"
Duration:
30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).
Alaska Content Standards Addressed in this lesson:
