A tornado is born from a powerful storm called a supercell. Tornadoes have been reported in all states, but most tornadoes happen in the central parts of America called “Tornado Alley”. In some supercells, warm, moist air rises quickly into the atmosphere. Winds blowing at different speeds at different parts of the supercell produce wind shear and cause a horizontal, rotating column of air. A funnel cloud will form as the air column rotates faster and more tightly within the supercell. The rain and hail within the storm cause the funnel cloud to touch the ground resulting in a tornado. The strength of a tornado is measured by what’s called the Fujita scale. The weakest tornadoes (F0) feature winds of 40-78 miles per hour, while the strongest tornadoes (F5) have winds of up to 318 miles per hour. All tornadoes can be devastating, especially if they touch down in areas with lots of people.
Tornado Outbreak
A tornado outbreak occurs when one storm system produces multiple tornadoes. Some tornado outbreaks can result in the formation of dozens of tornadoes over several states. One particularly powerful tornado outbreak occurred between April 25 and April 28 of 2011, where a record 355 tornadoes in 21 states and Canada were recorded, an including an F5 tornado that completely destroyed parts of Tuscaloosa, Alabama. Much of the destruction was caught on camera and broadcast across the country and Internet. The same weather system produced hailstones that measured 4.5 inches across in southern Virginia. 328 people were killed as a result of the outbreak, which totalled over $11 billion in damages.
Answer the following questions
- Which is not true about tornadoes?
a They are born from supercells
b Tornado strength is measured on the Fujita Scale
c Most tornadoes occur in North America in Tornado Alley
d They only occur in some states - What states have never had tornadoes?
a All states have had tornadoes
b The passage doesn’t say
c States outside of Tornado Alley
d Alaska and Hawaii - What causes the supercell to tilt downward towards the ground?
a warm air
b rain and hail
c wind
d lightning - When are tornadoes most devastating?
a When they register on the Fujita Scale
b When wind shear occurs
c When they hit areas with lots of people
d When they hit in Tornado Alley - Which of the following would complete the analogy?
Supercell : Tornado :
a Thunder : Rain
b Cloud : Lightning
c Moon : Stars
d Hurricane : Ocean
