Slow Start to Tornado ‘Season’ but Watch out for April

Slow Start to Tornado ‘Season’ but Watch out for April

So far it has been a relatively quiet tornado year across the U.S. with no EF-3 or stronger tornadoes yet reported, the latest in the year for such since at least 1950. However there are almost three weeks left to go in what historically has been one of the deadliest months for tornado outbreaks.



Satellite image of the Southeast on the afternoon of April 27, 2011 during the peak of one of the worst tornado outbreaks in U.S. history. It was the 2nd (or tied for 2nd) deadliest April tornado outbreak on record and the 4th deadliest such for any month of the year. Image from Wikicommons.

The ‘modern’ era of tornado observations is generally accepted as beginning in 1950 when the U.S. government-funded ‘Tornado Project’ was implemented with the establishment of an observational network of 134 stations and 34 cooperative stations across Oklahoma and Kansas. These sites were devoted to reporting, analyzing, and forecasting tornadoes. In 1953 the Severe Local Storms Center (SLSC) was established as part of the U.S. Weather Bureau and also in that year the first popular yet scholarly book about tornadoes was published by the University of Oklahoma Press, Tornadoes of the United States by Snowden Flora. Tornado research and forecasting efforts continued in earnest throughout the 1950s and 1960s and, in 1971, the eponymously named Fujita Tornado scale (after Univ. of Chicago physicist Tetsuya Theodore Fujita) the official ranking of tornado intensities began. The Fujita Scale was modified in 2007 to fine-tune tornado damage assessments and re-named the Enhanced Fujita Scale, or the EF ranking now in use. Although 1950 is used as the baseline for compiling modern tornado statistics there are good records of tornado events going back to 1680. Virtually every single one of these has been exhaustively researched by a modern-day ‘Tornado Project’ organization founded by Thomas P. Grazulis who compiled a list of all known ‘significant’ (F-2 or EF-2) tornadoes ever reported and published the data in his book Significant Tornadoes: 1680-1991. The information has been continuously updated on the Tornado Project web site linked to above.

Although (as of April 9th) there have been no reports of EF-3 or stronger tornadoes so far this year, and this is the latest such since 1950:



Graphic courtesy of The Weather Channel.

…looking at the Grazulis data we see a number of years with later dates for a first F-3 tornado occurrence. To wit:

1. June 6, 1874
2. May 6, 1910
3. May 1, 1915
4. April 28, 1902
5. April 23, 1926
6. April 18, 1877
7. April 15, 1900
7. April 15, 1887
9. April 13, 1883
10. April 12, 1941
10. April 12, 1881
(today = April 9, 2014 – would be 12th 1871-2014)
12 (13). April 8, 1896
13 (14). April 7, 1903
14 (15). April 6, 1872

Of course, in the 19th century there were large areas of tornado country (in the Plains) that were not as densely populated as today and many EF-3 or stronger tornadoes may have occurred in unpopulated areas or simply were never reported because they did no damage. Also, obviously, the advent of tornado radar detection and other modern weather observation systems did not exist until at least 1950, so this also has to be taken into account.

Given the above caveats we can say with some confidence that the 2014 tornado season is off to an unusually and temperate start.

The key word above is “start”. Historically, April is one of the deadliest months of the year for tornadoes and 7 of the top 20 deadliest tornado outbreaks in U.S. history have occurred during April. Below is a list below of April’s top ten deadliest tornado outbreaks on record:



The death statistics in the above table are from Grazulis ‘Significant Tornadoes: 1680-1991’ and may vary according to other sources. For the April 2011 event the death toll includes storm-related but not tornado-related fatalities. The number of deaths caused directly by tornadoes stands at 324. It is not entirely clear if the fatalities for the other events include storm-related deaths or tornado only such.

KUDOS: Thanks to Jon Erdman, Stu Ostro, and Nick Wiltgen at The Weather Channel.

Christopher C. Burt
Weather Historian