1. Thunderstorms
Small intense systems that can produce strong winds, rain, lightning and thunder.
Need 2 conditions
Air near surface needs to be warm and moist
The atmosphere must be unstable

2. Becoming unstable…
The surrounding air is colder than the rising air mass
This makes that rising air CONTINUE rising
The thunderstorm occurs when the air is rising rapidly
Forms cumulonimbus cloud

3. Lightning!
Electrical charges build up near the tops and bottoms of clouds heading from positive to negative to positive (opposites attract)
Flash of light occurs when a charge sparks
The flash heats the air to about the temperature of the surface of the sun
ENERGY IS RELEASED

4. Effects Thunderstorms can have positive or negative effects
Positive – rain can provide water for crops and restore lakes and streams
Negative
Flash floods
Winds
Hail
Lightning

5. Funnel Cloud v. Tornado
Wind traveling in 2 different directions causes it to start spinning
The updrafts of air push the spinning column down, sometimes to the ground
It is called a tornado once it hits the ground
Funnel cloud Tornado

6. Tornadoes Cumulonimbus clouds can sometimes form tornadoes
Only 1 percent of thunderstorms form tornadoes

7. Formation About 75 percent of tornadoes happen in the United States.
Warm humid air comes up from the Gulf of Mexico and meets cold dry air from Canada in the plains.

8. Effects Winds usually average around 95mph
Most are small and last only a few minutes
Larger ones are less common (20%) are strong enough to knock over trees, lift cars or take roofs off houses.
Very few (1%) are violent enough to lift or completely demolish sturdy buildings and can last more than two hours

10. Path
A tornado moves along with its thunderstorm, it travels fast and weaves a path that is impossible to predict
Tornado watch
When the weather conditions might produce tornadoes.
Tornado warning
When a tornado has
been detected

11. Hurricanes Most powerful storms on Earth Different names
Typhoons – Pacific Ocean
Cyclones – Indian Ocean
Form over warm tropical oceans
5o – 20o North and South
Vary in size
160 km to 1,500 km in diameter
Can travel thousands of miles

13. Formation of Hurricanes
Hurricane Season – August to October
Begins as a group of thunderstorms
Energy
Comes from condensed water vapor
Energy moves from ocean water into the air
Strong Winds Develop
Coriolis effect bends the wind
Fuel
Direct contact with warm ocean water
Hurricanes will continue to grow until they lose their source of warm, moist air

14. Hurricane Features

15. Effects of Hurricanes Wind Speed Can cause damage in a variety of ways
120 km/h to 300 km/h
Can cause damage in a variety of ways
Lift Cars
Produce tornadoes
Uproot Trees
Tear roofs off buildings
Heavy rains cause rivers to overflow
When a hurricane moves into a coastal area it causes a storm surge
Storm surges can rise sea level and have large waves (1m to 8m)
National Hurricane Center tries to warn people in time.

17. Winter Storms Formed when two air masses collide.
A continental polar air mass forming over snow is especially cold, dry, and dense.
It forces moist air to rise very quickly.

18. Blizzards
A storm with falling or blowing snow, winds at least 35 mph, reduced visibility and intense cold.
Occur in many parts of the Northern and Central United States.

19. Formation of a Blizzard
When warm air collides with cold air and is forced to rise above the colder air, the warm air brings moisture.
This moisture is formed normally by the wet air moving from the South or by blowing across large bodies of water.
A lift is created to raise moist air to form clouds and create ice and snow.

20. Duration of a Blizzard
For a storm to be considered a blizzard it has to last at least 3 hours.
Some blizzards can last for a few hours or even days!

21. Dangers of Blizzards
Whiteout conditions make it hard to see when traveling.
Strong winds and cold temperatures can create dangerous wind chill temperatures.
Roads can be slippery to drive on.
Power outages can occur due to strong winds and heavy snow.
Pipes can freeze and fuel
sources can be cut off.

22. Dust Storm
Strong, violent winds that carry fine particles like silt, clay, sand and dust-filled air over an extensive area.

23. Formation of a Dust Storm
Any area with a lot of dust and sand particles
Need dry air – No precipitation or water vapor in the air
Lots of wind
Huge
Can spread over hundreds of miles
Powerful
Wind speeds of at least 25 miles per hour (40 km)

24. Dangers of a Dust Storm Arrive without warning
Create large wall of dust and debris.
Last only a few minutes
Leave debris behind
Hard to see during storm
Breathing is impacted.
Takes fertile top soil away and reduces future crops.
Current crops are covered with dust.