What is severe weather?

Weather that poses a danger.

Mr. Fetch’s Earth Science Classroom

What is a thunderstorm?A storm that produces: 1. Lightning

2. Thunder 3. Heavy Rain and/or flooding

4. Strong winds and possibly hail

They last about 15-60 minutes.

Mr. Fetch’s Earth Science Classroom

How do thunderstorms form? When warm, moist air is lifted up violently.

The air rises up to form a cumulonimbus cloud.

If the winds are over 58 mph, the thunderstorm is said to be a SEVERE THUNDERSTORM.

How does lightning form?

Updrafts and downdrafts of wind and rain

cause different parts

of a cloud to become

electrically charged.

- (+) charge at top of cloud

- (-) charge at bottom of cloud

•Every second between a lightning flash and thunder means the storm is 1 mile away.

Speed of Light: 186,000 miles/second or 300,000 km/second

Speed-of-sound: 1100 ft/sec (330 m/sec)

How Far Away is Lightning?

The odds of becoming a lightning victim in the U.S. in any one year is 1 in 700,000.

The odds of being struck in your lifetime is 1 in 3,000.

Man Struck by Lightning

Talking on the telephone is the leading cause of lightning injuries inside the home

Standing under a tall tree is one of the most dangerous places to take shelter outside

Is Your Car Safe Video?

Lightning Facts

NO SUCH THING AS HEAT

LIGHTNING = FAR AWAY

THUNDERSTORM

Thunder Caused by the rapid expansion and

contraction of the air surrounding a lightning bolt.

Tornado: A rotating column of air.

1. Wind shear causes air to rotate.2. The rotating column of air is lifted by updrafts3. The column of air touches the ground = tornado

How are tornados classified?

3 out of every 4 tornadoes in the world happen in the United States

A Tornado in Oklahoma once destroyed a whole motel. People later found the motel’s sign in Arkansas

The United States have an average of 800 tornadoes every year

The chances that a tornado is a F5, the highest classification for a tornado on the F-scale, is less than 0.1%

A Tornado can occur at any time, but most often between 3pm and 9pm

Storm Chasing - your future career?http://www.youtube.com/watch?

v=bhGWWY1nCWw&feature=relmfu

Hurricanes

http://www.cbsnews.com/htdocs/natural_disasters/hurricanes/framesource_flash.html

Low Pressure Systems Associated with hurricanes

Strong winds and bad weather Move Counterclockwise

5 Things a Hurricane needs to Form

Progression to a Hurricane

Saffir-Simpson Scale is used to measure a hurricane’s intensity

Most dangerous part of hurricanesStorm SurgeStorm Surge – like what – like what happened with Hurricane happened with Hurricane Katrina Katrina

An abnormal warming of surface water ocean waters in the Eastern Tropical Pacific.

Occurs every 2 - 9 years or so….

• Droughts in Australia, Indonesia, Pacific NW of US. • Heavy storms resulting in flooding in California,

Midwest US and Central Europe and Asia.

Happens when the eastern Pacific is unusually cold after being unusually hot for years.