Prior to 1990, there is a likely undercount of tornadoes, particularly E/F0–1, with reports of weaker tornadoes becoming more common as population increased. A sharp increase in the annual average E/F0–1 count by approximately 200 tornadoes was noted upon the implementation of NEXRADDoppler weather radar in 1990–1991.[8][note 5] 1974 marked the first year where significant tornado (E/F2+) counts became homogenous with contemporary values, attributed to the consistent implementation of Fujita scale assessments.[12][note 4] Numerous discrepancies on the details of tornadoes in this outbreak exist between sources. The total count of tornadoes and ratings differs from various agencies accordingly. The list below documents information from the most contemporary official sources alongside assessments from tornado historian Thomas P. Grazulis.
Color/symbol key
Color / symbol
Description
†
Data from Grazulis 1990/1993/2001b
¶
Data from a local National Weather Service office
※
Data from the YYYY Storm Data publication
‡
Data from the NCEI database
♯
Maximum width of tornado
±
Tornado was rated below F2 intensity by Grazulis but a specific rating is unavailable.
List of confirmed tornadoes in the tornado outbreak (sequence) of Month-DD–DD, YYYY
$ (YYYY USD) $Format price error: cannot parse value "Error when using {{Inflation}}: |value= (parameter 2) and |start_year= (parameter 3) must be specified." (2024)
^All losses are in 1957 USD unless otherwise noted.
^An outbreak is generally defined as a group of at least six tornadoes (the number sometimes varies slightly according to local climatology) with no more than a six-hour gap between individual tornadoes. An outbreak sequence, prior to (after) the start of modern records in 1950, is defined as a period of no more than two (one) consecutive days without at least one significant (F2 or stronger) tornado.[1]
^ abAll dates are based on the local time zone where the tornado touched down; however, all times are in Coordinated Universal Time and dates are split at midnight CST/CDT for consistency.
^ abThe Fujita scale was devised under the aegis of scientist T. Theodore Fujita in the early 1970s. Prior to the advent of the scale in 1971, tornadoes in the United States were officially unrated.[2][3] Tornado ratings were retroactively applied to events prior to the formal adoption of the F-scale by the National Weather Service.[4] While the Fujita scale has been superseded by the Enhanced Fujita scale in the U.S. since February 1, 2007,[5] Canada used the old scale until April 1, 2013;[6] nations elsewhere, like the United Kingdom, apply other classifications such as the TORRO scale.[7]
^ abThe National Oceanic and Atmospheric Administration's Storm Data publication does not list exact damage totals for every event, instead giving damage categories. As such, damage for individual tornadoes is not comprehensive. Cite error: The named reference "NCEI" was defined multiple times with different content (see the help page).
^All starting coordinates are based on the NCEI database and may not reflect contemporary analyses
^The listed width values are primarily the average/mean width of the tornadoes, with those having known maximum widths denoted by ♯. From 1952 to 1994, reports largely list mean width whereas contemporary years list maximum width.[13] Values provided by Grazulis are the average width, with estimates being rounded down (i.e. 0.5 mi (0.80 km) is rounded down from 880 yards to 800 yards.[14][15]
^Edwards, Roger (March 5, 2015). "Enhanced F Scale for Tornado Damage". The Online Tornado FAQ (by Roger Edwards, SPC). Storm Prediction Center. Retrieved February 25, 2016.
— (July 1993). Significant Tornadoes 1680–1991: A Chronology and Analysis of Events. St. Johnsbury, Vermont: The Tornado Project of Environmental Films. ISBN1-879362-03-1.
