Severe Weather!!!!!!! Chapter 20.3

The main types of severe weather are: What is severe weather? Weather that poses a danger. The main types of severe weather are: Thunderstorms Tornadoes Hurricanes

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. Mr. Fetch’s Earth Science Classroom

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

Mr. Fetch's Earth Science Class 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 - Mr. Fetch's Earth Science Class

How Far Away is Lightning? 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)

Struck By Lightning!!! The odds of becoming a lightning victim in the U.S. in any one year is 1 in 100,000. The odds of being struck in your lifetime is 1 in 3,000. https://www.youtube.com/watch?v=L1HhRAUqFqM https://www.youtube.com/watch?v=ltK5c60nBHQ

The Safest Place? https://www.youtube.com/watch?v=bKczulzP5wk 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 https://www.youtube.com/watch?v=bKczulzP5wk

NO SUCH THING AS HEAT LIGHTNING = FAR AWAY THUNDERSTORM 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.

How does a tornado form? Tornado: A rotating column of air. 1. Wind shear causes air to rotate. 2. The rotating column of air is lifted by updrafts 3. The column of air touches the ground = tornado

Tornadoes are usually associated with severe thunderstorms.

How are tornados classified?

Interesting Tornado facts 3 out of every 4 tornadoes in the world happen in the United States The United States have an average of 800 tornadoes every year A Tornado can occur at any time, but most often between 3pm and 9pm 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 in Oklahoma once destroyed a whole motel. People later found the motel’s sign in Arkansas

Storm Chasing - your future career? http://www.youtube.com/watch?v=bhGWWY1nCWw&feature=relmfu

Hurricanes A tropical area of low pressure that forms over warm water Wind speeds must be higher than 74 mph. Usually given alphabetical names for convenience Slow moving storm: Lasts for days. Pushed by the easterly trade winds.

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

5 Things a Hurricane needs to Form

Progression to a Hurricane Disturbance Depression Tropical Storm Hurricane

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

Storm Surge – like what happened with Hurricane Katrina Most dangerous part of hurricanes Storm Surge – like what happened with Hurricane Katrina L