Winds can exceed 300 mph!Winds can exceed 300 mph! Around 1,000 occur on average each year in the Around 1,000 occur on average each year in the

U.S.U.S. On average, they kill 80 and injure 1,500 people On average, they kill 80 and injure 1,500 people

each yeareach year Can have a path up to a mile wide!Can have a path up to a mile wide! Can occur any time of the year, but peak during Can occur any time of the year, but peak during

the spring (March-June)the spring (March-June) Occur most frequently in the central U.S. in a Occur most frequently in the central U.S. in a

region nicknamed “Tornado Alley”region nicknamed “Tornado Alley”

What Exactly Is A Tornado?What Exactly Is A Tornado?

Rapidly whirling, funnel-shaped cloud that Rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud to touch reaches down from a storm cloud to touch Earth’s surface.Earth’s surface.

How Do They Form?How Do They Form? Actually, no one knows for sure!Actually, no one knows for sure! But…We have a pretty good idea…But…We have a pretty good idea…

Step 1Step 1 Before a thunderstorm, a change in wind direction and an Before a thunderstorm, a change in wind direction and an

increase in speed forms an invisible, horizontal spinning increase in speed forms an invisible, horizontal spinning effect in the lower atmosphere (at the base of the storm)effect in the lower atmosphere (at the base of the storm)

For example, a wind at 1,000 feet above the surface For example, a wind at 1,000 feet above the surface might blow at 5mph and a wind at 5000 feet might blow at might blow at 5mph and a wind at 5000 feet might blow at 25mph. This causes a horizontal rotating column of air.25mph. This causes a horizontal rotating column of air.

Step 2Step 2

Rising air within the thunderstorm (updrafts) Rising air within the thunderstorm (updrafts) tilts the rotating air from horizontal to verticaltilts the rotating air from horizontal to vertical

Step 3Step 3

Vertical rotation now extends 2-6 miles up into Vertical rotation now extends 2-6 miles up into the thunderstorm. Now a tornado may form the thunderstorm. Now a tornado may form and extend from this area of rotation to the and extend from this area of rotation to the ground.ground.

How Strong Are Tornados?How Strong Are Tornados?

Strength is measured by the Fujita Scale...Strength is measured by the Fujita Scale... F0 = weakest, F5 = StrongestF0 = weakest, F5 = Strongest All tornados are potentially deadly, but most All tornados are potentially deadly, but most

are actually relatively weak (74%)…!are actually relatively weak (74%)…! Only 1% of all tornados fall in the F4 – F5 Only 1% of all tornados fall in the F4 – F5

rangerange

Quick ReviewQuick Review

Are most tornados strong or weak?Are most tornados strong or weak? Which would cause more damage, an F1 or an Which would cause more damage, an F1 or an

F5 tornado?F5 tornado? During which season do most tornados occur in During which season do most tornados occur in

the U.S.?the U.S.? What is the nickname of the region in the U.S. What is the nickname of the region in the U.S.

where many tornados occur?where many tornados occur? What is used to classify the intensity of What is used to classify the intensity of

tornados?tornados? Bonus**: How do experts think tornados form?Bonus**: How do experts think tornados form?