Thunderstorms :

Aim: What are the ingredients of a thunderstorm?

Describe all of the events you see, feel and hear during a storm.

What is a storm?

A storm is a severe disturbance in the atmosphere.

Types of storms include: Thunderstorms Tornados Hurricanes

How is a thunderstorm formed?

A cold air mass runs into a warmer air mass and pushes the warm air up rapidly.

Thunderstorms occur along cold fronts.

Cumulonimbus clouds form, dropping heavy rain

Storm front (cold front) – where air masses with very different properties collide

How does lightning form? Lightning is created when

negative charges in the bottom of clouds are attracted to the positive charges on the ground

Lightning and Thunder Lightning animation

What is thunder?

Thunder is the rapid expansion of air molecules that happens when lightening rapidly heats the air around it.Thunder always accompanies lightning because it is the lightning that causes it.

Thunder animation

What else can form in a thunderstorm?

How does hail form?

Hail is formed when updrafts in a thundercloud carry raindrops upwards into extremely cold areas of the atmosphere where they freeze into lumps of ice.

The lumps fall to earth at very high speeds (up to 120 miles per hour).

The largest hailstone ever recorded measured over 5.6” in diameter and weighed almost 2 pounds (Ouch!).

How does hail form?

See A thunderstorm!

Observe an animation of a thunderstorm.

Summary: What are the ingredients of a thunderstorm?

Cold Air mass Warm Air mass Cold front Moisture in the air Lightning Thunder

Cumulonimbus clouds

Hail Tornados

Why is their hair standing on end?

Thunderstorm Safety

Read the article and answer the following questions:

Where is the best protection from a thunderstorm?

If outside, where should you go? If in a group, what should you do? If you feel your hair stand up…what should

you do?

25 million cloud-to-ground lightning strikes occur in the U.S. each year

The air within a lightning strike can reach 50,000 degrees Fahrenheit

Lightning heats its path 5 times hotter than the surface of the sun

One ground lightning stroke can generate between 100 million and 1 billion volts of electricity

Lightning safetyDon’t touch metal objects (they conduct electricity).

Find a low area – make yourself as small as possible

Stay away from other tall things – like trees and telephone poles

Spread out from a group

Tornados

A rapidly whirling, funnel shaped cloud that reaches the ground

VERY strong, fast winds Form from thunderhead

clouds called “super cells”

“Tornado alley” is in the Great Plains – more tornados than any other place in world

http://www.classzone.com/books/earth_science/terc/content/visualizations/es2006/es2006page01.cfm?chapter_no=visualization

Tornados

Tornado watch – means they are possible Tornado warning – its been spotted on ground Safety - Best place to be is in a basement Little flooding threat Unpredictable – form from thunderstorms Narrow path of destruction Fast moving Often in spring – when the seasons are changing

Hurricanes

Travels NW to NE steered by prevailing winds

June – November Evacuations may be

necessary near coast because of storm surge.

Go to interior room away from windows

Hurricanes Starts as a tropical

depression (low pressure), then tropical storm

Very low pressure in the eye – most dangerous winds are in the NE half of the eye wall.

Maritime tropical air mass Loses its energy as it is

farther from warm water Most damage done by

storm surge (flooding)

http://www.classzone.com/books/earth_science/terc/content/visualizations/es2008/es2008page01.cfm?chapter_no=visualization

http://www.brainpop.com/science/weather/hurricanes/