Collecting and Evaluating the Data

Data was collected from NOAA’s National Weather Service Storm Predeiction Center (http://www.spc.noaa.gov/wcm/#data) and subset to contain all tornados occuring in the past 20 years. The first 20 observations of the resulting data set can be seen in Figure 1.1.



Figure 1.1

Length len for each tornado was given in miles, so for closer evaluation of the time each tornado spent on the ground len was converted to yards and the variable yds was added.


Figure 1.2 shows a Kernel Density Estimation (KDE) for the length in yards for each tornado. The blue overlay shows that the length follows an exponential distribution. This is to be expected. Tornadoes occuring in the past 20 years have had a mean length of 4720 yards.



Mapping the Data

The following section contains spatial mapping of tornadoes for both the United States and the State of Alabama.
Figure 2.1 shows a graph of the average number of tornados that occured in each state over the last 20 years.




Figure 2.2 shows tornado tracks for the state of Alabama.