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3.2.19 Tornado
Calculated Priority Risk Index
3.70 High
Planning Significance
Description
The National Weather Service defines a tornado as “a violently rotating column of air extending
from a thunderstorm to the ground.” Tornadoes are the most violent of all atmospheric storms
and are capable of tremendous destruction. Wind speeds can exceed 250 mph, and damage
paths can be more than one mile wide and 50 miles long. In an average year, more than 900
tornadoes are reported in the United States, resulting in approximately 80 deaths and more than
1,500 injuries. High winds not associated with tornadoes are profiled separately in this
document in Section 3.2.21 Windstorm.
Although tornadoes have been documented on every continent, they occur most frequently in
the United States east of the Rocky Mountains. Kansas is situated in an area that is generally
known as “Tornado Alley.” Climatologically conditions are such that warm and cold air masses
meet in the center of the country to create conditions of great instability and fast-moving air at
high pressure that can ultimately result in the formation of tornado funnels.
Most tornadoes and tornado-related deaths and injuries occur during the months of April, May,
and June. However, tornadoes have struck in every month. Similarly, while most tornadoes
occur between 3:00 and 9:00 p.m., a tornado can strike at any time.
Location
Tornadoes can happen anywhere in the planning area. Figure 3.75 shows the tornado activity
in the United States. Region L shows 5 – 10 recorded EF3 – EF5 tornadoes between the years
1950 and 2006.
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