1. Thunderstorms, Hurricanes, and Tornadoes
Severe Weather
Thunderstorms, Hurricanes, and Tornadoes

2. Remember…
Energy is ALWAYS trying to equalize out, dangerous events happen in the process of energy trying to find balance in the universe!

3. Storms Definition: any disturbance or instability of the atmosphere
Formation: when a high pressure system moves into and around a low pressure system
Characteristics: formation of storm clouds (cumulonimbus) and mild/strong winds

4. Types of Storms Ice Storms Blizzards Hail Storm Thunderstorm
Hurricanes
Tropical Cyclones
Tornadoes

5. Thunderstorms
Formation: hot, moist low pressure system collides with cold, dry high pressure system
Characteristics: storm clouds (cumulonimbus), thunder, lightening, strong winds, precipitation
Microbursts = strong wind gusts, last < 3 sec
Updrafts and Downdrafts
Start forming in tropical rainforests and move to middle latitudes where they meet a cold, dry front.

8. Microbursts and Their Effects
A powerful downdraft of wind that happens only for a few seconds, normally invisible
Downdraft comes out of storm clouds
Discovered due to air plane crashes that were taking off during thunderstorms

10. Lifecycle of a Microburst

11. Science of Lightning
Cumulonimbus clouds have positive and negative charges in them.
Negative charges are at the bottom of the cloud
Positive charges are at the top of the cloud
Opposite Attraction between cloud and ground
Cloud sends out “feeler or stepped leader” of negative charge
Ground sends out a “positive streamer”
Meeting in the Middle “feeler-streamer”

15. Fun Facts about Lightning
A lightning charge contains 30 million volts at 100,000 amperes.
The total energy in a large thunderstorm is more than an atomic bomb.
About a hundred U.S. residents are killed by lightning every year.
The Empire State Building in New York City is struck by lightning about 25 times every year.
Air around a lightening bolt is heated to 54,000oF (5X hotter than the sun)
Lightning bolt is usually less than 2cm in diameter

16. Hurricanes Formation
Heat and evaporation off the water of the oceans creates a low pressure region
High pressure systems moves toward the low pressure area creating heavy winds
Winds flow inward towards the center and up the eye

17. Characteristics of Hurricanes
600 miles wide
Winds range from mph
Move at 10-20mph
Form over 80oF water
Formation starts between 5-15o latitude north/south of equator
Season in Northern Hemisphere:
Atlantic June 1 to Nov 30th
Pacific May 15th to Nov 30th

18. Hurricane Structure

19. Katrina (2005)

21. Hemispheres and Hurricanes
Northern Hemisphere (counterclockwise)
Coriolis Effect
Path = clockwise
Rotation = counterclockwise
Southern Hemisphere (clockwise)
Coriolis Effect
Path = counterclockwise
Rotation = clockwise
Note: the path of a hurricane is opposite the direction the hemisphere is spinning, but the rotation of any cyclone is the same as the rotation of the hemisphere that it is in.

23. Formation of Tornadoes
Cold, Dry Fronts collide with Warm, Moist Fronts
Upper horizontal wind rotation goes vertical
Column of vertically rotation air grows closer to ground out of a cumulonimbus cloud until it touches down to the ground

26. The Fujita Scale
Fujita Scale

27. 1884

29. Weather Alert System
Watches: are statements that tell us that conditions are favorable for storms to form
Warnings: are statements that describe storms and severe weather are happening
Special Announcements/Advisors: are statements describing unusual or inconvenient weather conditions.

30. Questions to Answer
What way does the air pressure flow in all storms? Why does it work this way?
What do storms help the atmosphere do once they happen and dissipate?

31. Reflection Questions
How well did you take notes? What was easy or hard about it?
Do you think you wrote down all of the important information?