Severe Weather

Hurricanes, Thunderstorms, and Tornadoes

Ingredients for a storm… Heat From the Sun Differences in Air Pressure Water

What is a hurricane? A hurricane is a large, swirling, low- pressure system that forms over the warm Atlantic Ocean.

Hurricanes form over warm ocean water. Near the equator, warm ocean water provides the energy that can turn a low pressure center into a violent storm. As water evaporates from the ocean, energy moves from the ocean water to the air. This energy makes warm air rise faster. Tall clouds and strong winds develop.

As winds blow across the water from different directions into the low, the Coriolis Effect bends their path into a spiral. The winds blow faster and faster, around the low pressure area, which becomes the center of a storm system.

Parts of a Hurricane

Eye - The calm center of the hurricane. Eyewall - The wall of dense thunderclouds surrounding the eye. The strongest winds of the hurricane are in the eyewall. Spiral Rainbands - A series of long, spiraling bands of rain clouds in a hurricane.

What things make hurricanes loose strength? 1. Crumple a piece of paper, then flatten it out. Crumple and flatten it out again. 2. Spin a top on the flattened paper. 3. Spin a top on a smooth surface. Count the seconds until it stops spinning. What do you think? How does the texture of the surface affect the rate at which the top loses energy?

Why do hurricanes seem to die over land? As long as a hurricane is over water, the warm, moist air rises and provides energy for the storm. When a hurricane reaches land, however, its supply of energy disappears and the storm loses power.

Create a Model of a Hurricane! Using glue, blue construction paper, and cotton balls, create a model of a hurricane, labeling and explaining each part. You may use your graphic organizer for assistance!

Tornadoes Tornadoes form from severe thunderstorms. They are very destructive because they have a high energy density. They also don't last very long. This makes it hard to learn about them. Since scientists don't know much about tornadoes, it's also hard to forecast themform thunderstormsenergy densityforecast

Tornadoes The fastest recorded wind speed is 230 miles per hour and occurred in New Hampshire in Although, winds can get faster in tornadoes (OVER 300mph!). The windiest place in the world is in Antarctica. tornadoes

In severe thunderstorms, wind at different heights blows in different directions and at different speeds. This difference in wind speed and direction, called wind shear, creates a rotating column parallel to the ground.

A thunderstorm’s updraft can tilt the rotating column upward into the thunderstorm creating a funnel cloud. If the funnel comes into contact with Earth’s surface, it is called a tornado.

Tornado Alley This map shows where most tornadoes form in the United States. The red area is known as "Tornado Alley". Warm moist air from the Gulf of Mexico collides with Cold dry air.

Thunderstorms It is late afternoon. The white puffy clouds that have been growing all day are replaced by a greenish sky. A distant rumble is heard...then another. It starts to rain. A flash of light streaks the sky, followed by a huge BOOM. Welcome to a thunderstorm.clouds rumble rainflash of light

Thunderstorms Thunderstorms are small, intense weather systems that produce strong winds, heavy rain, lightning, and thunder.

When do thunderstorms occur? Thunderstorms form from warm moist air and along cold fronts.

How are thunderstorms created? There are three ingredients for thunderstorms to form: 1. The air near the earth’s surface must be warm and moist. It rises or moves upward, which is called an updraft. 2. The atmosphere must be unstable- the surrounding air is colder than the rising air mass. As the warm air mass rises, it cools and turns into water vapor, condenses and forms CUMULONIMBUS Clouds.

Vertical Air Movement 3. As the cloud continues to build, ice particles form near the top of the cloud. As they get large-they form HAIL. As the ice particles or HAIL falls, cold air moves down with it, causing a downdraft.

Let’s Investigate! How do updrafts form??? Draw and describe what happens. In what ways is this demonstration of water similar to warm air in a thunderstorm? Challenge: How could you create a downdraft in this experiment?

Tornado Alley This map shows where most tornadoes form in the United States. The red area is known as "Tornado Alley". Warm moist air from the Gulf of Mexico collides with cold dry air.

The Water Cycle

Water never leaves the Earth. It is constantly being cycled through the atmosphere, ocean, and land. This process, known as the water cycle, is driven by energy from the sun. The water cycle is crucial to the existence of life on our planet. The Water Cycle Facts

The Water Cycle Evaporation

~During part of the water cycle, the sun heats up liquid water and changes it to a gas by the process of evaporation. ~Water that evaporates from Earth’s oceans, lakes, rivers, and moist soil moves into the atmosphere. Evaporation

Transpiration

The process of evaporation from plants is called transpiration. (In other words, it’s like plants sweating.)

Condensation

~As water (in the form of gas) rises higher in the atmosphere, it starts to cool and become a liquid again. This process is called condensation. ~When a large amount of water vapor condenses, it results in the formation of clouds.

Precipitation

When the water (whether it’s frozen or liquid) in the clouds gets too heavy, the water falls back to the earth. This is called precipitation.

Runoff

~When rain falls on the land, some of the water is infiltrated (or percolated) into the ground forming pockets of water called groundwater. ~Most groundwater eventually returns to the ocean. Other precipitation runs directly into streams or rivers. ~Water that collects in rivers, streams, and oceans is called runoff.

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