For clouds to form, air must be lifted Frontal Convectional Orographic

1. Orographic Lifting when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down, which can raise the humidity to 100% and create clouds and, under the right conditions, precipitation.

2. Convectional Lifting Earth’s surface is heated by the sun, which heats the air mass above it. The heated air near Earth’s surface rises and cool air sinks.

3. Frontal Lifting Warm air mass is pushed upward by cold air mass

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

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 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?

 About 54 people die by lightning strike each year in US  The odds of being struck in your lifetime is 1 in 10,000.  Man Struck by Lightning Man Struck by Lightning Lightning can be 5 times hotter than the surface of the Sun!

 Talking on a corded 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? Is Your Car Safe Video?

Lightning Facts NO SUCH THING AS HEAT LIGHTNING = FAR AWAY THUNDERSTORM If you hear thunder, then you are close enough to the storm to get struck by lightning!

 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 updrafts 3. 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?

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.

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 Low Pressure Systems  Associated with hurricanes  Strong winds and bad weather  Move Counterclockwise

5 Things a Hurricane needs to Form

Progression to a Hurricane DisturbanceDepression Tropical Storm Hurricane

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

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