Lesson 3What causes severe

weather?

How thunderstorms form

1.Moist air rises quickly

2. Air condenses-

forms clouds3. Precipitation (rain) falls

thunderstorms

diff. areas-diff.

charges(+ or -)

lightning= large,electrical spark moving betweenareas of opposite charges- heats air

How Thunderstorms Are Formed [01:43]

Make lightning

• Make Lightning!• The purpose of this experiment is to observe lightning formation. • Materials: Styrofoam plate, Thumbtack, Pencil with new eraser, Aluminum pie pan, Small

piece of wool fabric • 1. Push the thumbtack through the center of the aluminum pie pan from the bottom. • 2. Push the eraser end of the pencil into the thumbtack. (The pencil becomes a handle to lift the

pan.)• 3. Put the Styrofoam plate upside-down on a table. Rub the underside of the plate with the wool

for one minute. Rub hard and fast.• 4. Pick up the pie pan using the pencil "handle, " and place it on top of the upside-down plate.• 5. Touch the pie pan with your finger. If you don't feel anything when you touch the pan, try

rubbing the plate again.• Try turning the lights out before touching the pan. Do you see anything when you touch the

pan?• What happened when you touched the metal pie pan? What caused that?• How do you think this experiment relates to the formation of lightning? • It's all about static electricity! Lightning happens when the negative charges (electrons) in the

bottom of the cloud (and your finger) are attracted to the positive charges (protons) in the ground (and the pie pan). The resulting spark is like a mini-bolt of lightning.

• The accumulation of electric charges has to be great enough to overcome the insulating properties of air. When this happens, a stream of negative charges pours down towards a high point where positive charges have clustered due to the pull of the thunderhead.

• The connection is made and the protons rush up to meet the electrons. It is at that point that we see lightning. A bolt of lightning heats the air along its path causing it to expand rapidly. Thunder is the sound caused by rapidly expanding air.

Make lightning Make lightning

severe storm watch

•severe storms might form

??

severe storm warning

•severe storms have formed

•get prepared (get inside)

!!!

how tornadoes form

1. Layers of wind blow at different speeds &/or directions2. Column of air between starts to spin (funnel cloud)

3. Upward winds lift 1 end up- downward winds push other end down

How Tornadoes Develop [01:39

Tornadoes versus Hurricanes [00:34]

how hurricanes form

Get energy from warm, ocean water

Water vapor condenses forms clouds releases energy

fuel winds

Lose energy over land

How Hurricanes Develop [01:52]

hurricanetornado

•severe weather storms

•highly destructive•last for

minutes

•last for days

hurricane

•100’s km wide

tornado

•faster winds

•meters wide

The safest place to be during a tornado is in a basement.

No basement? Find shelter in a windowless room.

Gets energy from

warm, ocean water

Caused as a result of different areas having

different charges

When a funnel cloud

touches the

ground