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