Low number of U.S. tornadoes and tornado deaths over the past 12 months

After that historic May snow storm last week, it looks like our weather has finally turned the corner with much warmer weather and rain in the forecast now, not snow. Although some cooler temperatures are on the way for the rest of the week, it won’t be cold enough to snow (sigh of relief) and warmer temperatures return by the start of next week. Although it feels like we had to live through the longest winter ever, there was some good news from it.

All these statistics come from the National Weather Service. The period of time from May 2012 to April 2013 recorded the least number of EF-1 or stronger tornadoes on record in the United States going back to 1954. There was only 197 tornadoes during that time frame. The previous low for EF-1 and stronger tornadoes in a 12 consecutive calendar month period was 247 from June 1991 to May 1992. The 3rd lowest was 270 from November 1986 to October 1987.

The lack of tornadoes also meant a lack of tornado deaths in the country. From May 2012 to April 2012, the death toll was only 7. Statistics go back to 1875. This is the second lowest death toll for a 12 consecutive month death toll with the lowest being back starting in September 1899 when there were only 5. Third on the list are 8 deaths starting on August of 1991.

So why the lack of tornadoes and severe weather over the past 12 months? Well, last year in the summer of 2012 we were dealing with an extreme drought across much of the country with the worst of it over what’s considered tornado alley. Tornado alley runs up from Texas, north, in Iowa and southwest Minnesota. This area is favored for the development of tornadoes. The lack of moisture and dominating areas of hot high pressure kept stormy weather away. The dry conditions continued into the fall. This past winter was wet, and it got even wetter heading into the spring of 2013. While the drought has become less of an issue this spring, we still have not had much severe weather.

The first week of May only saw three tornadoes, which is the third-fewest number of tornadoes during the first week of May since record keeping began in 1950. Two tornadoes were in Florida and the other was in California. All three weak EF-0 tornadoes were far away from tornado alley, which is usually a hot bed for twisters this time of year. From 2003 to 2012, the average number of tornadoes for the first week of May is 73. The highest was the first week of May in 2003 when 239 tornadoes touched down.

The reason for this spring’s lack of severe weather has been not from drought but from unseasonably cold weather. April temperatures were well below normal across much of the Midwest, and we even had a snow storm in May. There was even snow for the first time on record in Arkansas in early May. So yeah, that kind of makes it hard for tornadoes to form. This is all pretty interesting considering, this minimum in tornado numbers comes only two years after the record maximum of 1,050 EF-1 and stronger tornadoes from June 2010 to May 2011. You can see this big swing on the graph below. Crazy, right?

So at least some good news came from this snowy and colder spring. While the weather has warmed up, the severe weather forecast does look fairly quiet in the next week. We’ll see what later in May brings.


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