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Storm observing stats: How hard is it to see a tornado?

By DAN ROBINSON
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(This post and stats are updated at regular intervals - last update was March 26, 2019.) I'm asked often the questions of how many tornadoes I've seen, and how difficult they are to see. I'm a stats/numbers type person, so I thought it would be fun to break the data down into tables. If you just want a quick answer, as of today I've seen 139 tornadoes, and I've averaged seeing a tornado on one out of every four tornado expeditions. On average, one out of every 5 tornadoes I see is "photogenic" (well-developed with good lighting and contrast). Some years have been better than that, others were worse (some I saw zero tornadoes!). On average, I put in around 10 tornado storm observation days per year (not including travel days). If you're interested in a more detailed answer than that, read on!

Below are tables breaking down tornado days by region, month, state and year. For the purpose of this data set, I'm not counting my numerous other expeditions for lightning, flooding, winter storms or general storm structure (those total in the dozens per year). This data also shows the average number of days one must expedition to see a tornado in different regions of the USA and at different times of year.

Before I get into the tables, here is how I define the metrics and data categories:

  • USA Tornado Event Regions: For the purposes of this post, I'm only highlighting regions where you have multiple realistic chances to see a tornado each year, if you are able to observe storms when the conditions come together. This map plots what I consider to be the USA's four 'tornado expeditionable' regions:
USA Tornado Event Regions

  • Tornado Event Days: For the purposes of this data set, I consider a Tornado Event Day to be one where there was tornado potential, and therefore my expedition objective/strategy was tornado-driven. I travel differently depending on what I expect storms to do, that is, I don't count my numerous lightning photography/shelf cloud/flooding expeditions to be 'tornado storm observation days' unless tornado potential materializes at some point during the expedition. As such, this data more accurately reflects my expedition-to-bust ratio when it comes to tornadoes only.
     
  • Tornado Days: These are defined as storm observation days where a tornado is seen, regardless of the number of tornadoes captured on that day.
     
  • Success rate: This is the percentage of tornado storm observation days that result in a tornado day. Again, for this calculation, each tornado day is counted only once, regardless of the number of tornadoes seen on that day.
     
  • Photogenic Tornadoes: This is a highly subjective metric, but one that I thought would be useful to include. That is, how much do you have to observe storms to see a "quality" event? For the purposes here, I define "photogenic" as a tornado that:
     
    1. has very little rain wrapping (or at least not enough to significantly impact visibility and contrast)
       
    2. is well-developed, that is, has a more or less "complete" structure with a continuous funnel and/or debris cloud from ground to cloud base
       
    3. lasts reasonably long enough to capture well-composed images and video, and
       
    4. occurs during bright daylight hours, resulting in pleasing lighting and contrast.

Annual Averages

Metric Overall
Average
Great Plains
Average
Midwest
Average
Tornadoes 6.9/year 5.3/year 3.1/year
Photogenic Tornadoes 1.6/year 1.3/year Every 2 years
Tornado Chase Days 11.1/year 5.8/year 10/year
Tornado Days 2.8/year 1.7/year 2/year
Tornadoes Per Tornado Day 2.5 3.1 0.6

Great Plains averages are calculated beginning in 2001. Midwest averages are calculated beginning in 2010, the year I moved to and began regularly observing in that region.

Tornadoes by Region - Leader: Great Plains

Region Tornado
Chase Days
Tornado
Days
Tornadoes Photogenic
Tornadoes
Success
Rate
%
Photogenic
Great Plains 111 33 101 25 32.7% 24.8%
Midwest 100 20 31* 5 20.0% 16.1%
South 1 0 0 0 0% 0%
East Coast 2 0 0 0 0% 0%
Total 211 53 132 30 25.1% 22.7%

The Great Plains in the spring is by far the most 'bang for your buck' in terms of the probability that you'll see a tornado on any given storm observation day. If I'm blessed enough to live a long life and am able to keep observing, the Midwest tornado numbers will continue to grow in relation the Plains. Overall, it takes twice as many storm observation days to see a tornado in the Midwest than the Great Plains, but each Midwest chase tends to involve half of the mileage of a typical Great Plains trip. All but 3 of the Midwestern tornadoes I've seen occured less than 2 hours from home! It's also worth noting that observing in Missouri (see the state-by-state table below) has really hurt the Midwest success rate. If not for Missouri, the Midwest rate would be very close to that of the Plains.

*30 of the 31 Midwest tornadoes were captured since 2010 (after I moved to the St. Louis metro area), and 25 of those 31 were captured in the state of Illinois.

Tornadoes by Month - Leader: May

Month Tornado
Chase Days
Tornado
Days
Tornadoes Photogenic
Tornadoes
Success
Rate
%
Photogenic
January 2 0 0 0 0% 0%
February 4 2 3 1 50% 33.3%
March 10 1 1 0 10.0% 0%
April 37 5 17 4 13.5% 23.5%
May 82 27 64 15 32.9% 23.4%
June 28 13 32 7 46.4% 21.9%
July 7 3 5 0 42.9% 0%
August 1 0 0 0 0% 0%
September 3 2 2 1 66.7% 50%
October 3 1 1 0 33.3% 0%
November 4 1 1 0 25.0% 0%
December 3 1 4 2 33.3% 50%

Of course, spring is the dominant season for severe storms, with May predictably on top for total tornadoes and the most photogenic tornadoes. Of note is the fact that I have had at least one tornado storm observation day in every month of the year. This is thanks to living in the Midwest, where many events are scattered throughout the entire year. All of my top 5 tornado intercepts have occurred in May.

Tornadoes by State - Leader: Kansas

State Tornado
Chase Days
Tornado
Days
Tornadoes Photogenic
Tornadoes
Success
Rate
%
Photogenic
Kansas 25 11 42 13 44.0% 31.0%
Oklahoma 40 8 25 5 20.0% 20.0%
Illinois 51 16 25 4 31.3% 16%
Texas 16 6 13 2 37.5% 15.3%
Nebraska 10 5 7 2 50% 28.6%
Colorado 5 3 7 3 60.0% 42.9%
Missouri 32 4 6 0 12.5% 0%
Wyoming 1 1 2 0 100% 0%
Iowa 3 1 1 0 33.3% 0%
South Dakota 2 1 1 0 50.0% 0%
Kentucky 7 0 0 0 0% 0%
Indiana 4 0 0 0 0% 0%
Ohio 2 0 0 0 0% 0%
Tennessee 2 0 0 0 0% 0%
Arkansas 2 0 0 0 0% 0%
North Carolina 2 0 0 0 0% 0%
Alabama 1 0 0 0 0% 0%
North Dakota 1 0 0 0 0% 0%

The leader in this category is no surprise: Kansas is the best state to cover in with the greatest number of tornadoes, most photogenic tornadoes and best overall success rate. But on this list, Illinois is catching up - in 2018, IL joined Oklahoma in a tie for second place for total sightings.

Also of note here is the surprising difficulty I've had seeing tornadoes in Missouri, despite a high number of storm observation days there (ranked number 3 in that category!). Part of this is due to the road network and terrain, but it's mostly because storms over there have simply not been very productive like they have in the states on either side. In fact, Missouri alone is really skewing my Midwest chase stats. I have a nearly equal success rate observing in Illinois as I do in all of the Great Plains.

Tornadoes by Year - Leader: 2016

Year Tornado
Chase Days
Tornado
Days
Tornadoes Photogenic
Tornadoes
Success
Rate
%
Photogenic
2001 4 0 0 0 0% 0%
2002 5 0 0 0 0% 0%
2003 10 0 0 0 0% 0%
2004 13 6 12 4 46.2% 33.3%
2005 8 3 14 2 37.5% 14.3%
2006 6 1 1 0 16.7% 0%
2007 6 3 15 0 50% 0%
2008 6 2 4 0 33.3% 0%
2009 7 0 0 0 0% 0%
2010 15 3 6 0 20% 0%
2011 10 2 2 1 20% 50%
2012 12 3 11 5 25% 45.5%
2013 22 6 12 4 27.3% 33.3%
2014 10 6 10 1 60.0% 10%
2015 14 4 6 0 28.6% 0%
2016 11 4 17 5 36.4% 29.4%
2017 11 5 9 4 45.5% 44.4%
2018 15 4 11 3 26.7% 27.2%
2019 4 1 1 0 25.0% 0%

This table only goes back to 2001, since that was the first year I expanded from just observing lightning to observing tornadoes and supercells. Prior to that, I was observing strictly for lightning photography. 2007 held the top tornado spot for a long time, but was finally bumped to #2 by the 2016 season. I had more tornado storm observation days (Plains and Midwest combined) in 2013 than I have in any other year in the past.

I'd be interested to hear if your tornado day to tornado storm observation day rates are similar to mine. Feel free to post your numbers!

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The following comments were posted before this site switched to a new comment system on August 27, 2016:

Wow! Great stats. My last 3 years as follows: Chase Days. Tornado Days. Tornadoes. Success 2011. 5. 1. 3. 20% 2012. 1. 0. 0. 0% 2013. 7. 5. 8. 62.5%
- Posted by Clarence from Nashville, Tn

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