Tornadoes – Nature’s Most Violent Storms
Tornadoes occur in many parts of the world; however, the most destructive ones are found in the United States east of the Rocky Mountains. Peak tornado months in the southern states are March through May, while peak months in the northern states are during the summer.
Tornadoes are most likely to occur between 3:00 p.m. and 9:00 p.m. but have been known to occur at all hours of the day or night. In an average year, over 800 tornadoes are reported nationwide, resulting in 80 deaths and over 1,500 injuries.
A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 miles per hour or more. Paths of damage can be in excess of one mile wide and fifty miles long. Once a tornado in Broken Bow, Oklahoma, carried a motel sign 30 miles and dropped it in Arkansas!
Specific weather conditions consistent with thunderstorm activity produce tornadoes. Thunderstorms develop in warm, moist air in advance of eastward moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes.
Before thunderstorms develop, a change in wind direction and an increase in wind speed create an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical. An area of rotation two to six miles wide extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.
Tornadoes take on many shapes and sizes. They are categorized as weak, strong, or violent. Weak tornadoes account for 69% of all tornadoes. Their lifetime is one to ten minutes, with winds less than 110 miles per hour. Strong tornadoes account for 29% of all tornadoes. They may last twenty minutes or longer, with winds 110 to 205 miles per hour. Violent tornadoes account for only 2% of all tornadoes but are the cause of 70% of all tornado deaths. These tornadoes can exceed one hour in length, with winds greater than 205 miles per hour.
There are many myths surrounding tornadoes and tornado safety. One is that areas near rivers, lakes, and mountains are safe from tornadoes. The fact is no place is safe from tornadoes. In the late 1980s, a tornado swept through Yellowstone National Park, leaving a path of destruction up and down a 10,000 foot mountain.
Another common myth is windows should be opened before a tornado approaches to equalize pressure. Opening windows is not a good idea. It allows damaging winds to enter the structure. If a tornado is coming your way, leave your windows alone and quickly get to a safe place.