Do Tornados Really Sound Like Freight Trains

Do Tornados Really Sound Like Freight Trains??

• http://www.interaxs.net/pub/hgr/xenia_tornado.mp3

• What do you think after listening to the Xenia Tornado of April 3, 1974?

Winds can exceed 300 mph!!!

• Winds can exceed 300 mph!!!

• Around 1,000 occur on average each year in the U.S.

• Kill 80, injure 1,500 people each year on average

• Can have a path up to a mile wide!!!

• Can occur any time of the year, but peak during the spring (March-June)

• Occur most frequently in the central U.S. in a region nicknamed “Tornado Alley”

What Exactly Is A Tornado?

• Violently rotating column of air (Vortex) extending from a thunderstorm to the ground

How Do They Form?

• Actually, no one knows for sure!

• But…We have a pretty good idea…

Step 1

• Before a t-storm, a change in wind direction and an increase in speed forms an invisible, horizontal spinning effect in the lower atmosphere (at the base of the storm)

Step 2

• Rising air within the t-storm (updrafts) tilts the rotating air from horizontal to vertical

Step 3

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

Convection Demo

• Same basic principle behind a tornado vortex (funnel; column of fire in this case)

• Warm air moves up the vortex (updraft)

• Cools and sinks as it funnels out of the top (downdraft)

• The more air drawn in = faster and tighter spin

• This is called a convection cycle

How Strong Are Tornados?

• Strength is measured by the Fujita Scale...

• F0 = weakest, F5 = Strongest

Are Most Tornados Strong?

• All tornados are potentially deadly, but most are actually relatively weak (74%)…!

• Only 1% of all tornados fall in the F4 – F5 range

What’s Up With Xenia, OH?

• Xenia has been the target of several major tornados down through the years…

• Most recent: Sept. 2000

• Most Notable: April 3, 1974

Sept. 2000 Damage

April 3, 1974 Tornado

April 3, 1974 Damage

Answers

• Sept. 2000 = F3-F4 (Severe/Devastating Damage; Winds of 200-260 mph)

• April 1974 = F5 (Incredible Damage; Winds of 260-300+ mph!!!)

Quick Review

• Are most tornados strong or weak?

• Which would cause more damage, an F1 or an F5 tornado?

• During which season do most tornados occur in the U.S.?

• What is the nickname of the region in the U.S. where many tornados occur?

• What is used to classify the intensity of tornados?

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

THE END