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.
It would seem that this correlates with the severe drought conditions recently. Does also correlate in previous years?
It’s been the coldest spring in my memory.
Hot weather and cold fronts make for tornadoes.
Wait until it gets hot.
File under : “Probably Shouldn’t Have Said That”
Hurricanes are also off.
Drought is gonna be a bitch.
I live in tornado alley and so far the season has been way too cold. We just had some snow the other day which just isn’t common here. It’s normally around 100 degrees by now and we’re still fighting frost and 45-50 degree temps, with very occasional near 70’s and a couple of near 80 degree days. We’ve actually been getting moisture.
If it was hotter, it would be dryer so the cool is holding some moisture. BUT, all the groceries that should be ready now, aren’t. And the wheat production is suffering every bit as badly as if the drought were baking away.
We just haven’t had the heat mixed with the coldfronts to cause the wind and clouds to whirl about.
But when it does warm up, well, it’s hard to say right now. I think tornadoes are merely delayed, but I sure hope I am very wrong!
Same here we had 5 “of snow in NW AR the other day!
But is a good thing for the people but the weather bums have no death and destruction to report on and is the real jest of the article!
I suspect once it warms up it’s still gonna be a doozy of a season. May and June can still be very active months.
This year will be an active hurricane season according to weather predictors plus Joe Bastardi who is the absolute expert. He is seldom wrong and he says there will be more than average hurricanes.
I always find what his prediction is because I’m in the path of those that come into Galveston.
Tornado season more active = proof of global warming
Tornado season less active = proof of global warming
My view about that is a little “out there”, maybe later... :’)
Remember: it’s not global warming anymore...it’s “climate change”...so if it gets warmer, it counts...and if it gets cooler, it counts. If it stays the same...then “climate change” is merely in abeyance...just metaphorically catching it’s breath...get it?
Soon, the EPA will put tornadoes on the Endangered Species List.
The Immigration Transformation (Mark Steyn)
It’s time for Democrats to ditch Andrew Jackson
The Art of Death - The moderate Muslim majority is a myth.
Some noteworthy articles about politics, foreign or military affairs, IMHO, FReepmail me if you want on or off my list.
Thanks for the link.
I see you are an expert on global warming!
lol
My friend Sams sight.
I think the change this year is in part due to how the jet stream is tracking this year. Many other North American air currents are affected by what the jet stream is doing.
Certainly 2011 does appear to be have been unusual year in North American tornado history, and this year appears closer to norm, so far, and there was an article last year that related jet stream behavior and its seasonal variations to the occurance of tornados.
http://news.discovery.com/earth/frequent-tornadoes-a-symptom-of-jet-stream-change-110602.htm
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