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Severe Weather

Severe Weather. 7 th Grade Science Mrs. Loerakker. Tornado Video. Tornadoes are the most violent storms. They occur throughout the world, but are most abundant in the United States. 800 tornadoes are reported each year. There are 80 deaths and 1500 injuries each year due to tornadoes.

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Severe Weather

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  1. Severe Weather 7th Grade Science Mrs. Loerakker

  2. Tornado Video • Tornadoes are the most violent storms. • They occur throughout the world, but are most abundant in the United States. • 800 tornadoes are reported each year. There are 80 deaths and 1500 injuries each year due to tornadoes. • Check it out!

  3. What is up with the GREEN SKY?! • Tornadoes are not always accompanied by green skies. • Tornadoes can happen any time of the day, but usually happen later in the day when the Sun is setting and the horizon is red. • Light beneath a cloud is usually blue from the water in the cloud. • A blue object illuminated by red light creates the green sky.

  4. What Causes Tornadoes? • Late Winter/Early Spring: Cold fronts push warm air upward. This movement causes thunderstorms. Hail and/or tornadoes can form, as well. • Spring: In Central Plains warm, moist (east) air is separated from dry, hot air (west). This “dryline” can move eastward. • Rocky Mountains: Warm air is pushed up over mountains. • Can occur with tropical storms and hurricanes.

  5. Weak Tornadoes • 69% of all tornadoes • Less than 5% of tornado deaths • Last 1-10 minutes • Winds less than 110 mph • Over water these are called “waterspouts”

  6. Strong Tornadoes • 29% of all tornadoes • Less than 30% of tornado deaths • Last 20 minutes • Winds 110-205 mph

  7. Violent Tornadoes • 2% of all tornadoes • Less than 70% of tornado deaths • Can last up to an hour (or longer) • Winds greater than 205 mph

  8. How Tornadoes are Measured: The Fujita Scale • The original Fujita scale was devised in 1971 by Dt. T. Theodore Fujita from UC. • Tornadoes were rate F0 (weak)-F5(extreme damage). • Tornadoes winds were estimated by the type of damage the tornado caused. • This original scale did not accurately measure tornadoes in vacant areas, and surveyors could judge damage differently (it is somewhat subjective).

  9. Enhanced Fujita Scale-Implemented in 2007

  10. Top Ten Deadly Tornadoes

  11. Thunderstorms • Formed when warm, moist air is lifted upward. • Cumulonimbus clouds form producing lightning and rain (and sometimes hail).

  12. Tornado Alley Tornado Alley is a nickname for an area that consistently experiences a high frequency of tornadoes each year. The area that has the most strong and violent tornadoes includes eastern SD, NE, KS, OK. Northern TX, and eastern Colorado.

  13. How Does Lightning Form • Lightning is formed when water droplets moving within a cloud become electrically charged. • Usually the upper part of a cloud is positive (+), the lower part is (-). • Lightning charges between clouds or between clouds and the earth’s surface is big enough an electric discharge occurs.

  14. Thunder • Lightning causes a quick and rapid expansion of air molecules. • This causes a sound, we call thunder. • Since sound waves travel more slowly than light waves, we SEE lightning and then HEAR thunder. • The closer we are to the storm, the more closely we see the lightning and hear the thunder. • Check it out! • Check this out, too!

  15. Hurricane • A tropical cycle or a rotation like a tornado over warm, humid waters. • Hurricanes are named each year alternating men’s and women’s names. • Floods, high winds , landslides, and mudslides can accompany hurricanes. • Hurricanes are rated Category 1-5.

  16. Notification of Storms • From the National Weather Service: -WARNING: Issued when a weather event is occurring or has a high probability to occur. -WATCH: Occurs when the risk of a weather event has increased. The time and location are still uncertain. -ADVISORY: Issued for less serious occurrences. Caution should still be taken.

  17. Sources • http://www.nssl.noaa.gov/edu/safety/tornadoguide.html • http://www.news.wisc.edu/15301

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