Low Tornado Numbers and Low Tornado Deaths, May 2012-April 2013

Updated 10 May 2013 to add new information from April 2013

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:

217 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

 

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No Tornado Deaths in May 2012

In May 2012, there were no tornado deaths in the United States. How unusual was that?

We can look at the record of tornado deaths, discussed here, dating back to 1875. The last time there were no deaths in the month of May was in 2005. Prior to that, it was 1994. Overall, there have been 15 years in the 138 years of the record (1875-2012) with no deaths in the month of May, so we’d expect that to happen about once every decade.

May 2012 stands in dramatic contrast to May 2011, when 178 people died in tornadoes, 158 of them in the Joplin, Missouri tornado of 22 May. 178 deaths is the fifth highest death toll in the period 1875-2012, and the largest since 211 people died in 1933. The deadliest May on record was 1896, when 502 people were killed, including 255 in the Saint Louis, MO-East Saint Louis, MO tornado of 27 May. Adjusted for wealth of the country, that tornado was the costliest in US history, with damage adjusted to 2011 dollars of over $6 billion.

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10 May 2010 tornado outbreak

(This will be updated as more information and time to post become available. Given the local nature of the event, information may be obtained quickly, but time may be at a premium.)

A significant outbreak of tornadoes occurred over Oklahoma and southern Kansas on 10 May 2010. Numerous damaging, long-track tornadoes have been reported from the Red River on the southern Oklahoma border up through southern Kansas. As of 6 AM CDT, 11 May, there have been 37 preliminary tornado reports. This is likely to change following damage surveys that will begin later today. A very preliminary summary of information from the National Weather Service Forecast Office in Norman covering their region is available here. The Tulsa Forecast Office also has a briefing on the eastern Oklahoma portion of the outbreak.

At this time, there are five fatalities reported in Oklahoma, 2 from the Choctaw area of Oklahoma County and 3 from Tecumseh in Pottawatomie County.

VORTEX2 collected data on the storm that produced the Norman tornado east of Norman.

There were media reports of damage at the National Weather Center. These reports are untrue, although the tornado was visible from the NWC and debris could be seen as the tornado moved east of the NWC. In addition, some staff members suffered damage at their residences.

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US Annual Tornado Death Tolls, 1875-present

Updated 23 May 2013 to include data through 2012

One of the reasons that we started this blog was to provide basic information on severe weather and its impacts.  Frequently, we get questions along the lines of “What’s the average X per year?” For many different “X”es, this is not as easy of a question as it might appear.  In large part, this is because many of the things we deal with have large trends in them (severe weather reports per year), so that the “average” depends on how far back you go in the record.  In order to make it easy for people who want the data to get the answer they need, we hope to put some of those numbers online here.

The first dataset is the number of deaths per year from tornadoes in the United States. The National Weather Service archive goes back to 1950. Brooks and Doswell (2002) discussed the long-term history of tornado deaths, drawing on the work of Grazulis (1993) (Grazulis, T. P., 1993: Significant Tornadoes, 1680-1991. Environmental Films, 1326 pp.). Reasonably reliable estimates of deaths per year can be made back to about 1875 by using the Grazulis data.

The Brooks and Doswell paper had a graph of the annual death toll normalized by population of the US through 2000.  Here is an updated version (through 2008) of that figure, showing that the death toll per million population appears to have leveled off in the last decade or so.

The purple points are the annual death rates, the red line is a simple smoother, the solid black line is a long-term trend in two sections (1875-1925, 1925-2000) and the cyan lines are estimates of the 10th percentile and 90th percentile from 1925-2000. Brooks and Doswell (2002) have an extensive discussion of the record and its possible implications.

US Tornado Deaths Per Million People

At the end of this post, we have a table of the annual death tolls going back to 1875 (1875-1949 from Grazulis, 1950-2008 from the National Weather Service.)  Although the data represent our best understanding at this time, it is possible that the numbers could change, if additional information was found.  Occasionally, it’s discovered that a fatality associated with a tornado was missed or double-counted. We’ll correct such entries if we find about about them, but that will likely be a rare event.  The death tolls are for direct deaths, i.e., someone killed directly by the impact of the tornado.  It does not include indirect deaths, which might not have occurred if the tornado had not happened, but the tornado was not an immediate cause.  Examples of indirect deaths that have occurred include a heart attack upon seeing damage to a neighbor’s house, falls when going to shelter, and a fire caused by a candle lit when the power went out after a tornado.

YearDeaths
1875183
187651
187764
1878102
187985
1880256
188173
1882200
1883292
1884252
188558
1886129
188760
188848
188932
1890244
189136
1892114
1893294
1894124
189530
1896537
189760
1898162
1899227
1900101
190152
1902157
1903216
190487
1905184
190670
190780
1908477
1909404
191012
191155
1912175
1913346
191441
191584
1916150
1917551
1918136
1919206
1920499
1921202
1922135
1923110
1924376
1925794
1926144
1927540
192895
1929274
1930179
193136
1932394
1933362
193447
193571
1936552
193729
1938183
193991
194065
194153
1942384
194358
1944275
1945210
194678
1947313
1948139
1949211
195070
195134
1952230
1953519
195436
1955129
195683
1957193
195867
195958
196046
196152
196230
196331
196473
1965301
196698
1967114
1968131
196966
197073
1971159
197227
197389
1974366
197560
197644
197743
197853
197984
198028
198124
198264
198334
1984122
198594
198615
198759
198832
198950
199053
199139
199239
199333
199469
199530
199625
199767
1998130
199994
200041
200140
200255
200354
200435
200539
200667
200781
2008126
200921
201045
2011553
201270
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