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Chasing stats: How hard is it to see a tornado?

By DAN ROBINSON
Storm Chaser/Photographer
25 Years of Storm Chasing
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(This post and stats are updated after every tornado I see - last update was June 15, 2017.) 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 118 tornadoes, and I've averaged seeing a tornado on one out of every four tornado chases. 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 chase 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 chases 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 chase 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 Chase 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 chase when the conditions come together. This map plots what I consider to be the USA's four 'tornado chaseable' regions:
USA Tornado Chase Regions

  • Tornado Chase Days: For the purposes of this data set, I consider a Tornado Chase Day to be one where there was tornado potential, and therefore my chase objective/strategy was tornado-driven. I chase differently depending on what I expect storms to do, that is, I don't count my numerous lightning photography/shelf cloud/flooding chases to be 'tornado chase days' unless tornado potential materializes at some point during the chase. As such, this data more accurately reflects my chase-to-bust ratio when it comes to tornadoes only.
     
  • Tornado Days: These are defined as chase days where a tornado is seen, regardless of the number of tornadoes captured on that day.
     
  • Success rate: This is the percentage of tornado chase 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 chase 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.

Tornadoes by Region - Leader: Great Plains

Region Tornado
Chase Days
Tornado
Days
Tornadoes Photogenic
Tornadoes
Success
Rate
%
Photogenic
Great Plains 82 29 93 23 35.4% 24.7%
Midwest 85 17 25* 3 20.0% 12.0%
South 1 0 0 0 0% 0%
East Coast 2 0 0 0 0% 0%
Total 172 46 118 26 26.7% 22.0%

*24 of the 25 Midwest tornadoes were captured since 2010 (after I moved to the St. Louis metro area), and 19 of those 24 were captured in the state of Illinois.

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 chase day. If I'm blessed enough to live a long life and am able to keep chasing, the Midwest tornado numbers will continue to grow in relation the Plains. Overall, it takes twice as many chase 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 chase. All but 3 of the Midwestern tornadoes I've seen occured less than 2 hours from home! It's also worth noting that chasing 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.

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 6 0 0 0 0% 0%
April 36 5 17 4 13.9% 23.5%
May 75 25 58 13 33.3% 22.4%
June 24 12 31 7 50% 22.6%
July 3 2 4 0 66.7% 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 3 0 0 0 0% 0%
December 1 0 0 0 0% 0%

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 chase 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 24 11 42 13 45.8% 31.0%
Oklahoma 35 7 24 5 20.0% 20.8%
Illinois 41 13 19 2 31.7% 10.5%
Texas 15 5 12 2 33.3% 16.7%
Missouri 29 4 6 0 13.8% 0%
Nebraska 10 5 7 2 50% 28.6%
Iowa 3 1 1 0 33.3% 0%
South Dakota 2 1 1 0 50% 0%
Colorado 4 2 2 1 50% 50%
Wyoming 1 1 2 0 100% 0%
Kentucky 6 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 chase in with the greatest number of tornadoes, most photogenic tornadoes and best overall success rate. But on this list, Illinois is catching up - in 2015, IL passed Texas as the #3 state for total sightings. Again, provided that I'm able to chase here for many years to come, Illinois may end up contending for the #2 or even #1 spot someday.

Also of note here is the surprising difficulty I've had seeing tornadoes in Missouri, despite a high number of chase days there (ranked number 2 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 chasing 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 9 3 7 4 33.3% 57.1%

This table only goes back to 2001, since that was the first year I expanded from just chasing lightning to chasing tornadoes and supercells. Prior to that, I was chasing 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 chase 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 chase day rates are similar to mine. Feel free to post your numbers!

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

25 Years of Storm Chasing
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