For clouds to form, air must be lifted

FrontalFrontal

Convectional

Convectional

Orographic

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

LiftingEarth’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.

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?

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

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?

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 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 hurricanes

Storm SurgeStorm Surge – like what – like what happened with Hurricane happened with Hurricane Katrina Katrina