There is a weather phenomenon that occurs in the United States more than anywhere else on Earth. The US experiences about 75% of the world’s tornadoes. A tornado, of course, is a rotating column of air that moves very fast. It occurs because of a difference in pressure. At the center of a tornado is very low pressure, and at its edge is high pressure. This pressure difference between the two gives it incredible speed. A tornado that doesn’t reach the ground is called a funnel cloud, and a tornado that develops over water is called a waterspout.
A tornado’s intensity and strength are measured after it has done its damage. This is determined using the Enhanced Fujita Scale (EF). There are six categories to the EF Scale. EF0 has wind speeds up to 85 mph, while the strongest, EF5, has wind speeds at over 200 mph. In addition, there are three types of tornadoes-weak, strong, and violent. These are based on the damage the tornado has caused and how long it lasts.
Weak tornadoes are usually less than ten minutes and would be an EF0 or EF1. The majority of tornadoes are in this category. Strong tornadoes go 20 minutes or longer and are usually in the EF3 category. Violent tornadoes are the most deadly and have wind speeds greater than 205 mph, and can last over an hour. They’re in the EF4 and EF5 categories. Most of the tornadoes that occur in the US happen in the central part of the country, affectionately known as Tornado Alley.
