Tornadoes comes in different sizes, many as narrow rope-like swirls, others as wide funnels. Across the Plains, tornadoes can be seen from miles away. Across the eastern United States and the Deep South, tornadoes are often hidden in large swaths of rain and hail, making them very difficult to see, and thus even more dangerous. A majority of tornadoes are labelled weak with wind speeds of 100 mph or less, and are usually on the ground for a few minutes. Even weak tornadoes can produce substantial damage.
Some tornadoes intensify further and become strong or violent .
Strong tornadoes produce winds up to around 200 mph. Most of the Ohio tornadoes that produce major damage are labelled strong. Only a few tornadoes across the country each year are labelled violent with winds of 200 to 300 mph. These tornadoes produce catastrophic damage, and can be on the ground for half an hour or longer. An unstable airmass promotes the development of strong updrafts.