QOTW: More on January Tornadoes

Posted by pmarshwx on 17 Jan 2011 | 2 comments

The answer to last week’s “Question of the Week” sparked a lot of posts on Twitter and at least one question posed in the comments. These comments and questions got me thinking about more ways to dissect the tornado database. Thus, I thought for this week’s installment of QOTW, I would continue with the same theme.

Above is the image originally posted in the answer to last week’s question. It depicts the number of January tornadoes each year, broken down by F/EF-Scale rating. Although containing a lot of information, it fails to answer the question I received most often: “How many fatalities have resulted from January tornadoes?” There figure below displays the number of injuries and fatalities by year for 1950-2009. (Note: The y-axis is scaled via a square-root. The thin, smooth line is a smooth trend-line. Thanks to the fine folks on the “ggplot2” listserv for helping me debug an issue with this plot!)

After a small spike from the mid-1960s through the mid-1970s, injuries from January tornadoes decreased slightly and has held relatively steady around 20-25 per year. The exception to this was 1999, which holds the record for most number of January tornadoes, including the largest January tornado outbreak on record. Fatalities appear to follow a similar trend as injuries, albeit with much lower numbers. In total

• January Injuries: 2455 (40.9 per year)
• January Fatalities: 138 (2.3 per year)

We can break down January tornado casualties even more and examine them by F/EF-Scale ratings.

As one might expect, a general increase in casualties is found as F/EF-Scale rating increases. This leads me to this week’s questions.

Above is an image depicting the number of January tornadoes between 1950 and 2009 broken down by county. Using the above image as a guide, between 1950 and 2009:

1. Which state(s) had the most January tornadoes?
2. Which state(s) had the most January tornado injuries?
3. Which state(s) had the most January tornado fatalities?
4. Which state(s) had the most injuries per tornado?
5. Which state(s) had the most fatalities per tornado?

(Hint: A tornado that crosses a county boundary is counted in both counties. Thus, one cannot sum the number of tornadoes per county in a state to find the number of tornadoes per state.)