It has been nearly 2 weeks since a catastrophic tornado annihilated a significant chunk of Joplin, Missouri. This stunning and tragic event has generated a lot of discussion in meteorological circles about why it was so deadly. Now that I've had some time to gather information and reflect on this tornado, I thought I would share some thoughts.
I believe that several circumstances combined to make this tornado the deadliest in the "modern" era, or post-1953. Here are some of them in no particular order:
1. Rapid intensification - based on video/eyewitness reports/damage survey, this tornado rapidly morphed from a weak/small tornado into a monstrous wedge, and unfortunately this process happened right as the tornado was moving into Joplin.
2. Poor visibility - by this I mean 2 things. It appears the tornado was wrapped in rain from the vantage point of many of those in the path. Also, the sheer size of the funnel may have been deceptive to an observer expecting to see a more traditional looking funnel.
3. Exact track - although some loss of life with a tornado of this magnitude may be almost inevitable, it may have been less of a story if it tracked a few miles differently in either direction. The path just happened to be directly over numerous residential areas.
4. Wide swath of intense winds - Based on the damage survey, it seems as though a rather wide portion of the damage was in the EF3-EF5 range. Typically this is enough to cause total or near total building failure and when that occurs, the odds of survival decrease.
We can't blame this outcome on a lack of warning. The local NWS office issued a tornado warning with acceptable lead time and, in my opinion, did the best they could given the rapidly unfolding situation. Had the warning not come until later, even more people may have died. I truly believe this was mostly a case of bad luck, where a series of circumstances came together in just the right (or in this case wrong) way.
Great strides have been made in reducing the number of mass casualty tornado events, but I knew a day like this was only a matter of time. I did not think it would happen in this manner though. I really thought we had come far enough so that the next deadly tornado of this magnitude would only occur if it plowed through a major city or a crowded outdoor event like the Indy 500. The Joplin event obviously throws that thinking out the window. I think we can learn some lessons from this event; not only that, we should look to the past to get a sense of where these particularly fatal tornadoes have occurred and what the circumstances were. This will help us answer the question: Can it happen here?
The Joplin tornado is the 15th tornado on record to kill at least 100 people in the U.S. and the first since 1953. Here are the paths of all of these tornadoes (drawn to the best of my ability) and the years in which they occurred:
There are a couple things that stand out. Most of these tornadoes occurred in the 1800's or first half of the 1900's, and a majority of them have occurred east of the Plains. In fact, 10 out of 15 have taken place roughly along/east of the Mississippi River. The 1925 Tri-State tornado killed over 70 people in Indiana, making it the state's deadliest tornado to date.
Most of the 100+ fatality tornadoes passed through cities/large towns or had extremely bad luck associated with them (for example, a majority of the deaths in the 1840 Natchez, Mississippi tornado were boaters on the Mississippi River). Historical records are sketchy and possibly inaccurate, but based on the available information, these tornadoes had path widths anywhere between a half mile to almost 2 miles. So...intense, wide tornadoes tracking through highly populated areas seem to be the most likely candidates. Using SPC's Severeplot 3.0, I searched the Indiana records for these types of tornadoes. Here are the F4/F5 tornadoes with an average path width of at least a half mile (the blue boxes are explained below) since 1950:
Almost all of the wide, violent tornadoes occurred on April 11, 1965 and April 3, 1974. It's not a coincidence that those are 2 of our deadliest outbreaks. The blue boxes depict locations of greater population. Using historical cases, I believe that in order for a tornado to kill at least 100 people, it would likely have to pass through one of the boxes. That is NOT to say that any violent tornado that passes through there is going to kill that many people (thankfully!) but a tornado in those areas with circumstances similar to Joplin is one I would be very concerned about.
As you can see, we have been pretty lucky in terms of massive tornadoes avoiding those boxes, at least since 1950. We can be sure that our luck will run out one day, but hopefully we don't have to face anything on the scale of Joplin anytime soon. Given our ever increasing population, though, it is a possibility. The good news is that statistically speaking, these extreme killers are very rare and hopefully they stay that way.
