Posted on 05/05/2013 2:10:46 PM PDT by neverdem
Updated 2 May 2013 to correct typo on date of previous low tornado count
The 12-month period from May 2012 to April 2013 was remarkable for the absence of tornado activity and tornado impacts in the United States.
We can start by looking at the number of EF1 and stronger tornadoes during that period. A final count is available through January 2013 and we have a pretty good estimate of how many occurred in February through April, although final numbers won’t be available until July. Although the 12 month total may change a little bit with the final data, it’s unlikely to change enough to affect the results here.
From May 2012-April 2013, the estimate is that there were 197 tornadoes rated EF1 or stronger. Where does that stack up historically? Well, we have pretty good data back to 1954. During that time, the previous low for (E)F1 and stronger tornadoes in a 12 consecutive calendar month period was 247, from June 1991-May 1992. The next lowest (ignoring the overlapping periods, such as April 2012-March 2013) was 270 from November 1986-October 1987. The lowest non-overlapping 12 month counts on record from 1954-present, with the starting month, are:
197 May 2012 (preliminary)
247 June 1991
270 November 1986
289 December 2001
298 June 2000
This apparent record was set less than two years after the record for most EF1+ tornadoes in a 12-month period was set, with 1050 from June 2010-May 2011. The time series showing the evolution of the number of (E)F1+ tornadoes since 1954 is below. The number of (E)F1+ tornadoes in the 12 months beginning with the time on the x-axis is plotted for every month starting in January 1954 and ending in May 2012, the most recent point.
The death toll from May 2012-April 2013 was 7. National Weather Service official statistics go back to January 1950, but we can extend that by using the work of Tom Grazulis from the Tornado Project, who has collected tornado fatality information back into the 17th century. The data are reasonably good back to 1875, but it’s still possible that there are some missed fatalities, particularly as we go back farther in time. So, where does 7 fatalities in 12 consecutive calendar months stack up? Again, here are the lowest totals, going back to 1875, for 12 consecutive months, with the starting month. (For overlapping periods, such as April 2012-March 2013 and May 2012-April 2013, only the lowest period is listed.)
5 September 1899
7 May 2012
8 August 1991
12 November 1909
12 May 1940
This blog is intended to facilitate communication about the impacts of selected severe weather events, particularly major tornadoes, in the United States. We hope it will allow us to assist interested parties to understand what we at the NOAA Weather Partners in Norman, Oklahoma have been able to gather about the events. It is not intended to provide critical weather forecast information, nor is it intended to provide information on a broad range of research topics associated with severe weather.
Without really doing research, drought doesn’t seem to have a great effect on tornadoes.
1988-1990, for example, were drought years in much of the Midwest. There was not not a particularly low number of tornadoes.
Low tornado numbers in 2000 and 2001. Closest noticeable droughts were 1999 and 2002.
The 12-month period from May 2012 to April 2013 was remarkable for the absence of tornado activity and tornado impacts in the United States.
Oh no! Everybody run and hide. That damned Global Warming will kill us all.
hehe
Too bad they don’t teach the application of “regression to the mean” any more!
It must be global warming causing milder weather. I’m pretty sure the global warming models predicted that.
The reason I’m so sure? Because the global warming models have predicted everything EXACTLY like it’s been happening! Everything! (All predictions after the fact, of course.)
This is obviously caused by globull warming.
I really do hope you're right. Last spring and summer were terribly hot here (Virginia). But our March was the coldest on record, and here it is early May, and we have the heat on. That's a first.
Al Gore is Fat
Obviously a conspiracy headed by Bush and Cheney who manipulate their tornado, earthquake, blizzard, and hurricane machines on whims simply to drive people crazy. And since most libs are crazy, I guess their plans are working.
Thanks for the link.
I hope you are wrong too, but I feel when it gets hot and the cold fronts come in tornadoes will be back.
Thanks for the ping!
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