As a total number, tornadoes are more common in the United States than in any other nation. Australia is considered the runner-up, with nations such as India, Germany, Russia and the United Kingdom also the sites of many tornadoes each year. One of the worst months for US tornado activity was May 2003. During that month, 543 tornadoes were reported in the US, with the majority in the Midwest and the Deep South.
More facts about tornadoes in the US:
- A tornado is most likely to develop when an air mass that is warm and somewhat moist meets with a mass that is composed of cool and dry air. The resulting combination causes instability in the atmosphere that results in changes in wind direction and speed that create the funnels. A tornado might be somewhat small and die out within a matter of minutes or might be quite large and last for several days.
- Tornado season varies slightly from one region to the next. In the South, the period from March to May is considered the prime season for tornadoes, although some activity is expected during the hurricane season that begins in July and ends in October. People in the Plains states are more likely to see activity during May and the first part of June. The North and the upper portion of the Midwest experience peak conditions during the latter part of June and into July.
- "Tornado alley" is a term that is used to refer to a section of the Plains and Midwest reaching down to Texas. Activity in this area usually occurs but is not limited to the spring. "Dixie alley" includes parts of Tennessee, Mississippi, Kentucky and Alabama, and its tornado season occurs later in the year, with increased activity common toward the end of the Gulf Region’s hurricane season.
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More Info: http://spc.noaa.gov
Discussion Comments
@Grivusangel -- So true. Both of the Super Outbreaks in the Southeast in the past 45 years happened in April. We can usually breathe a little easier once we get into June, but spring can be a really scary time in the South.
I know after living through both Super Outbreaks, I can read the radar nearly as well as the weather people can, and I can walk outside and just about predict how severe the storms will be. I know when a severe thunderstorm warning really should be a tornado warning, and when I go into a place in the spring, the first thing I do is scope out potential hidey-holes if a storm comes. That's just how you think when tornadoes are common in your area. I'm sure the folks in Iowa, Nebraska and Missouri do the same thing.
The bit about Dixie Alley is a little misleading. Actually, we have two severe seasons: the first comes in March through May, and the second in late October through December. The second season is generally much less active, and the area only sees severe weather in connection with hurricanes if a hurricane actually makes landfall in one of the Southeastern states.
The issue is the transition between cool weather to warm in the spring, and warm weather to cool weather in the autumn, plus that giant bathtub cranking out humidity called the Gulf of Mexico. You start getting air masses that are very cool moving into warm, humid air, and vice versa. We just know to be wary when the weather gets unseasonably warm and humid. Bad things are apt to happen.
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