Tuesday, April 19, 2011

Historic 3 Day Tornado Outbreak!

Above is the preliminarily tornado reports from April 14th - April 16th. There is no doubt this was a historic tornado outbreak, but how historic was it?

April 14th: 28 tornado reports
April 15th: 132 tornado reports
April 16th: 129 tornado reports

First, remember these are only reports. This contains several "double/triple" tornadoes and also probably some tornado reports that weren't actually tornadoes. I would personally say about 70% of the preliminary tornado reports verify as actual tornadoes these days. To the best of my knowledge, the all time 3 day tornado outbreak was back on May 28th - 30th 2004, where there were 184 confirmed tornadoes. On a side note, May 29th 2004, was the greatest tornado chase of my life, as I honestly don't know how many tornadoes I saw? LOTS! The day was highlighted by two massive wedge tornadoes I saw in Argonia, KS & Conway Springs, KS... I'll leave a link to some amazing video below!

So how does this outbreak stack up? Well, it will probably take another week or so to know for sure, but let's use the 70% verification rule for the purpose of this post.

Total 3 day preliminary reports: 289 tornado reports

At 70%, you would get 202 confirmed tornadoes! That's amazing, and would easily set the record for confirmed tornadoes over a 3 day outbreak! Definitely historic, but let's not get too crazy with this. This was not Super Outbreak II! I don't say that in a critical way at all, but keep in mind that while I have little doubt 148 tornadoes in a 24 hours period will be broken someday, I seriously doubt you will ever see 6 F5's (today EF-5's) and 24 F4's (today EF-4's) in a 24 hour period! Is it possible, sure... But I would argue that is at least a one in a 100 year event! Plus, even then, it's not just about the total numbers, these tornadoes would have to hit enough infrastructure to obtain those insane ratings. Again, not impossible, but very unlikely! Think about it, 6 EF-5's & 24 EF-4's in a 24 hour period? Before I go, check out this really cool map made by Victor Gensini. It needs to be updated again, but it really shows you the scope of this historic outbreak!

*UPDATE* It looks like I'm going to be off with the 70% verification rate. I should have considered factors like population & the explosion of social media these days a lot more than I did! It looks to verify closer to 50%, which means the record of 184 tornadoes in a 3 day outbreak is safe. This outbreak was still historic though! On a side note, just to show how much times have changed, just look back to the May 28th - May 30th 2004 outbreak. 206 reported tornadoes, with 184 confirmed tornadoes. I know that was in the Plains, but that's still 89.3%...


  1. Greg, just to follow up on your math:

    Saturday (April 16) saw a total of 52 tornadoes confirmed between Maryland, Virginia, North Carolina, and South Carolina. The SPC has 137 tornado reports for Saturday among these states (which encompass all of the tornado reports for that day).

    Based on this, the actual percentage of tornadoes is closer to about 38%. I don't know how the previous two days' worth of reports match up versus confirmed tornadoes, but extrapolating Saturday's reports suggest you might be overestimating the total number of tornadoes a bit.

    Even so, that 52 from Saturday puts you almost 1/3 of the way toward the record.

  2. I'm a little surprised it was only 38% for Saturday. Historically, the percentages are much higher than that. So it really has nothing to do with my math, as I'm just going off average statistics. Maybe this event was just an anomaly for tornado reports? Either way, at this rate I don't see it breaking 184 tornadoes. We'll see how it ends, but I doubt it will reach the record...

  3. Patrick Marsh touched on this in a blog post recently, but considering just 5 years ago the SPC storm reports were underreporting actual tornadoes as opposed to overreporting, I wonder how reliable that 70-75% figure is. I'd bet that the continued proliferation of cell phones and social media will drive that percentage down even further.

    When you consider the population density of the mid-Atlantic relative to the plains (or even the southeast in some parts), I wouldn't be surprised to see the number land closer to 50% over the long term.

  4. I agree with you Dan, as you make some excellent points! 50% is probably going to be a better percentage these days, especially in heavier populated areas and with the explosion of social media. I guess I should have thought more about that! Things sure change quick though... Just look at the May 28th-30th 2004 outbreak. I know it is the Plains, but you had 206 reports with 184 confirmed tornadoes. That's 89.3%...