A tornado spins near Wray, Colorado on May 7, 2016. (Dale Kaminski via Flickr)
We talk a lot about tornadoes here. While it’s not always an egg to chicken type of deal, most tornadoes come after tornado warnings.
That in mind, there are a lot more tornado warnings than tornadoes. In fact, on average, about 2.5 times more. It is true that false alarms and missed tornadoes are still commonplace. But the biggest and the baddest, the ones coming to cause real trouble, are increasingly well predicted.
In any threat environment, there will be more warning than actual threat. It keeps those trained to keep a watchful eye on their toes, and maybe even does the same for the rest of us as well.
There are a lot of ways we could look at warnings. They’re a personal interest of mine, but by no means am I am an expert. I covered the innovative way the National Weather Service is implementing #StormWarningTwitter last year over at the Capital Weather Gang. That’s a subject I hope to return to soon. In the meantime, there was some playing around to be done with polygons.
I’m going to keep it brief, but everything could use some framing.
Let’s start with the image above. It’s a generalized representation of where tornado warnings are most expected based on (short and probably biased in spots) history (I’m looking at you northern Arizona). What you see is based of a fairly large grid, which keeps things extra general.
[Americans are getting less advance notice for tornadoes, as researchers struggle to understand why]
It washes out facts like the one in which I live in a tornado warning dead zone in the middle of Washington, D.C. But warnings are relatively frequent in the area. It only goes back to 2008, because that’s the first year storm based warnings were nationally implemented. There are storm based warnings prior, but in the interest of keeping it straightforward I am pretending they do not exist. (Iowa Environmental Mesonet has an awesome tool you can play with)
The basic gist of nine years of storm based tornado warnings is that the Mid-South is more or less ground zero for tornado warning frequency. Part of this is the length of the season in that region. In some ways, tornadoes are a constant threat there. While there is a bit of a slumber in summer and fall (unless there are hurricanes), the zone can stay active throughout winter in many years. From there, we see other hot spots in the Midwest and Plains.
Now let’s take a look at each year since 2008. I’m going to try to make it a practice to come back here and update this at the end of each year going forward. Fingers crossed. 😉
2008 – 4,701 tornado warnings
Before 2011, there was 2008. Barrages of tornadoes came throughout the 2000s and into the early 2010s, but 2008 and 2011 stand above the rest. By actual numbers, it fell just short of 2011 with 1,688 tornadoes vs. 1,691. On warnings, the difference was just 50, with 2008 taking the top spot at 4,701. A similar ratio. A very red map. Too much death and destruction, but less than there would have been without the NWS effort to save life and property.
2009 – 3,231 tornado warnings
Compared to what we’ve seen the past few years prior to 2017, this was an active season. In reality, it was more or less average and arguably below average in the typical “tornado alley” of the Plains. Dixie Alley is almost always a tornado warning leader, but this year was particularly stacked in that direction.
2010 – 3,447 tornado warnings
2010 was a big season in spots, and on the high side of average overall when it came to tornadoes. A North Dakota NWS office leading the pack for tornado warnings is unusual in this sample that spans nearly a decade. The northern Plains/Midwest was an area that saw an unusually active tornado season, with several notable outbreaks scouring the landscape.
2011 – 4,651 tornado warnings
“On paper” 2011 and 2008 are virtually tied when it comes to total tornadoes and total tornado warnings. Seasons like these are made at the margins. 2011 ended up with 84 EF3+ tornadoes (23 of which were violent EF4 or EF5 events). 2008 had “only” 59 EF3+ and 10 violent tornadoes. It’s those strongest tornadoes that cause the most grief, hence the large gap in deaths (550+ in 2011 and 126 in 2008) between these two terrible years.
2012 – 2,420 tornado warnings
We started this web site and the related adventures five years ago this year. 2012 got off to a big start with outbreaks in February and a major one in March, then another in April. After that? Not a lot. Thanks, ustornadoes.com.
2013 – 1,831 tornado warnings
The biggest tornado outbreak of 2013 didn’t come along until November. If the map wasn’t enough to tell you it was a fairly quiet year, that fact should help out. The November outbreak was a huge one for the time of year, with 75 tornadoes reported. Other than a two-week period in May in which the infamous Moore (EF5) and El Reno (EF3) tornadoes occurred, the typical hot spots were unusually tornado free.
2014 – 1,873 tornado warnings
2014 picked right up where 2013 left off. This was near the peak of the long-term drought over parts of the Plains, so much of that region was unusually quiet. When storms were not sparse, humidity was not at its typically potent level, leaving supercells with bases way too high to produce tornadoes under rational conditions. Things get a little less rational on the High Plains, and that was one zone which saw tornado warnings fly.
2015 – 2,328 tornado warnings
After a lengthy spell of wondering where tornadoes went, they came back in 2015. A big reason was an energized southern stream as El Nino fueled moisture streamed into the United States. Oklahoma and Texas had crazy flooding through much of the spring. Wherever there is flooding, there are storms. Storms in April and May equals tornadoes. A Christmastime volley of deadly tornadoes capped off the year in an unfortunate way.
2016 – 2,050 tornado warnings
Although drought was mostly dead in the Plains and would eventually be on its way to dying out west, it was another year in a persistent and largely below average stretch. Few if any remarkable events occurred until May arrived. About a week of tornadoes peaked during an outbreak across western Kansas, which helped elevate the Dodge City office on the list for the year.
2008-16 – 26,532 tornado warnings
In the period of 2008 through 2016 much of the country east of the Rockies is colored in some level of ominously-shaded red. Regions of the Mid-South and Gulf Coast saw the most overall warnings during the period.
Possible trends
This is an admittedly small sample to assess trends, especially given the erratic nature of tornado activity year-to-year. As such, there’s no point in dedicating a lot of time to it.
A possible takeaway is that we are now seeing fewer tornado warnings to tornadoes. Without examining false alarm and success rates, this may not mean a lot. While there is some evidence that lead times are not as good at they once were, it may be that more quick and weak tornadoes are recorded now than in the past.
As forecasting skill increases, it is logical that there will be fewer tornado warnings that do not result in tornadoes, which should also mean a smaller ratio of warnings to tornadoes.
So far, there have been 934 tornado warnings issued (through April 20) during 2017. Tornado numbers have been running at a top-end pace all year as well, so it will be interesting to see how it continues to progress.
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Interesting maps. No doubt improved forecasting reduces false positives. To a lessor degree, do you think there may also be a political / PR factor tempering alerts where big government stands behind the system? Come Ian, I know you must have thought about this ;)