Download Key Points on Tornadoes and Hurricanes

Name: ____________________________________
Period: ____
Key Points on Tornadoes and Hurricanes:
1. Tornadoes develop out of thunderstorms. Thunderstorms are the result of warm, moist,
low pressure air that rises. This is called an updraft.
a. When winds produced by the storm blow in opposite directions, the air can
begin rotating horizontally to the ground.
b. As updrafts push higher, the rotating air is pushed into a vertical position. This is
called a mesocyclone and is basically a large turning cloud in the sky. This is
likely to form a tornado.
c. When cold air from high in the atmosphere begins to sink toward the ground
(downdraft), it can bring part of the mesocyclone to the ground turning it into a
tornado.
d. Wind speeds range from 100 MPH to 300 MPH.
e. Tornadoes usually occur in the Midwestern and Southeastern United States
during the spring and fall.
2. Hurricanes develop over warm tropical oceans that are at least 80°F. Most hurricanes
that impact the U.S. start as thunderstorms off the coast of Africa. These are called
tropical disturbances.
a. These thunderstorms have low pressure and very moist air. As the air rises, it
condenses forming clouds. This releases heat which further lowers the pressure
causing the air to rise more.
b. Cold, dense air rushes down from high in the atmosphere causing wind. This
cold air is heated by the water and begins to rise, creating a cycle with larger
and larger clouds forming and winds increasing in speed.
c. The moving air is impacted by the Coriolis effect which causes it to begin
rotating counterclockwise.
d. While the disturbance is over warm water, it will continue to strengthen. When
winds reach 74 MPH, it is declared a hurricane.
Tornadoes and Hurricanes: Independent Practice
Answer the following questions as a scientist would. Explain WHY using COMPLETE sentences!
1. What must be present for a tornado to form?
2. What is a mesocyclone? Is this a tornado?
3. What causes a tornado to touchdown on the ground?
4. When and where are tornadoes likely to form?
Name: ____________________________________
Period: ____
5. What must be present for a hurricane to occur?
6. Where are most hurricanes “born”?
7. What causes a hurricane to rotate?
8. When is a tropical depression declared a hurricane? What causes this to occur?