1. Severe Weather Thunderstorms Lightening & Tornadoes
Sixth Grade
GPS Earth Science
Pam Myers

2. THUNDERSTORMS Caused by quick, upward movement of warm, moist air
Occurs along a cold front within a warm air mass
Air is heated by Earth’s surface

3. Thunderstorms Lightning Produced by electrons
Flows from a negatively-charged area
To a positively-charged area

4. Lightning: an electric current
many bits of ice bump into each other
collisions create an electric charge
cloud fills with electrical charges
the positive charges form at the top
the negative charges form at the bottom
opposites attract
causes a positive build up on ground beneath the cloud
ZAP! Lightning Strikes!

5. Thunderstorms Lightning Either in a cloud or on the ground
Causes air to expand rapidly – bright flash
Ground’s electrical charge concentrates around anything that sticks up
The charge coming up eventually connects with a charge reaching down from the clouds

6. Thunderstorms Thunder Caused by rapid expansion of air
Produced by lightning bolt
If you hear the sound of thunder, then you are in danger from lightning.
Lightning kills/injures more people each year than hurricanes or tornadoes (between people)

8. Thunderstorms SAFETY TIPS
You Must Avoid
using electrical appliances (includes telephone)
being near tall objects (like under a tree)
open spaces (crouch down and hug your knees
being near or in bodies of water
all conductors of electricity!
Lightning may be about to strike if
your hair stands up (feels prickly)

10. Thunder Is Caused By Lightning
Lightning bolt travels (cloud to ground)
Opens a channel (a little hole in the air)
Super heated air expands
Quickly cooled air collapses back due
Sound wave is thunder
Light travels faster than sound
Lightning before we thunder
Which do you think is hotter, a bolt of lightning, or the surface of the sun?
Lightning- it is 30,000 degrees Celsius. That’s 5 times hotter than the sun!!

12. # Seconds / 5 = how many miles away
Can you tell how far away a thunderstorm is?
Count the number of seconds between when you see lightning & hear thunder
# Seconds / 5 = how many miles away
For example:
If you counted 10 seconds between the lightning and the thunder, the lightning is 2 miles away!

13. TORNADO (Twister or Whirlwind)
Rotating, funnel-shaped cloud
Usually Midwestern USA
Diameter: several hundred yards
Develops during a thunderstorm
Air Pressure
Rapid drop
causes rain & hail
Wind speed ranges mph
Lasts about 10 minutes (THANK GOODNESS!)

14. TORNADO Tornado Watch Tornado Warning
Conditions are right for one to occur
We’re watching for one!
Tornado Warning
One has been sighted
Take cover!

15. Tornado SAFETY TIPS Move to underground area (basement)
If outdoors, get in a ditch -- not under a bridge
If no basement, lie flat beneath a table or bed
Go to central part of building
Stay away from windows
Get out of car or mobile home
Crouch in the SW corner
debris usually fall in the NE corner

16. change in wind direction
How do tornadoes form? Wind shear
change in wind direction
an increase in wind speed with increasing height
creates an invisible, horizontal spinning effect in lower atmosphere
Rising air from the updraft of a thunderstorm tilts the rotating air from horizontal to vertical.
An area of rotation, 2-6 miles wide, now extends through much of the storm.

17. The Fujita Scale
Theodore Fujita

18. What NOT to do
(8 min video)
Moore, OK time-lapsed 3 min.

19. Where are tornadoes most likely to occur?
The Great Plains of the central the United States brings ingredients together.
includes TX, KS, and OK.
More than 500 tornadoes in this area annually , commonly known as "Tornado Alley".