Yes, we found that it is much more likely for a tornado to occur in the afternoon hours between 12:00 and 21:00 local time than night/morning hours. Out of the 70,858 total tornadoes included in the dataset, these 10 hours account for 78.53% of total tornado touchdown times. The most common time for a tornado to touch-down is between 17:00 and 18:00 where 8,468 tornadoes or 11.95% of all tornadoes have occured over the past 70 years. This suggests that afternoon times are more likely to have thermodynamically favorable atmospheric conditions for tornado formation than other times. This is extremely important since this is when people commonly return from work and kids return from school. It is imperative that families and homeowners have tornado action plans for their homes since a tornado is statistically more likely to occur when they are at home. Furthermore, this data implies that it would be a worthwhile investment to install a storm shelter or a similar structure in one's home. We hope that this data prompts citizens to be extra vigilant for tornadoes during afternoon hours.
Although tornadoes are able to occur at any time of the year, we found that a tornado season does in fact exist within the United States. Qualitatively, peak tornado season seems to take place between April, May, and June. Quantitatively, these three months account for 55.16% of all tornado activity, or 39,087 out of the 70,858 total tornadoes in the dataset. The science behind this phenomenon is that energy imbalances between the northern and middle latitudes peak during spring months. This combines with the unique geography of the United States to cause large scale synoptic environments that are conductive for tornado formation. The main takeaway from this data is that people must always be on the lookout for tornadoes at all times of the year, but that they must be particularly observant during spring months.
Our data says definitely yes. By plotting the number of tornadoes per year and doing a linear regression on the data, we found that the number of tornadoes that occur each year has been increasing at a rate of about 15 tornadoes a year (14.993 to be exact). One might think that climate change is responsible for this increase, but this regression also provides that at year 0, the number of tornadoes that occured would have been -28,741.53. After investigating this relationship further, we determined that the likely reason for this increase is because of better technology and reporting. The advent of mobile doppler radar has made it easier to confirm tornadoes, especially for tornadoes that occur over sparsely populated land. Additionally, more amateur tornado spotters have started chasing tornadoes in recent years leading to even more confirmed tornado reportings.
The main difference between EF and F rated tornadoes, is that EF rated tornadoes are rated based on the destruction they cause whereas F rated tornadoes are rated on peak wind speeds. This means that EF rated tornadoes are much more likely to be correlated with the damage they cause than F rated tornadoes. This relationship is seen in this graph, which shows the average property damage caused by tornadoes at each rating in the EF and F rating scales. The EF rated tornadoes consistently have higher average property damage than the F rated tornadoes of the same level. For example, EF5 rated tornadoes average $413,715,384 of damage per tornado whereas F5 rated tornadoes average $33,031,716 of damage per tornado. One example of this difference is how the El Reno in 2013 was rated EF3, but had F5 wind speeds. The wind speeds of this tornado were estimated at over 300mph (an extremely strong F5 tornado), but was only given an EF3 rating. This is because the tornado largely passed over unoccupied farmland, making the destruction relatively minimal. If this tornado had passed over a populated area, it would have easily been given an EF5 rating since the destruction would have been much larger. This explains why EF rated tornadoes have a higher average property damage at each level than F rated tornadoes.
F3+ (and EF3+) rated tornadoes are classified as significant tornadoes opposed to F0, F1, and F2 tornadoes. This graph shows qualitatively that as the number of total tornadoes has been increasing per decade, the number of significant F3+ tornadoes has remained relatively the same, even decreasing a little. The largest proportion of F3+ tornadoes occurred during the 1950s when 39.69% of all tornadoes were F3+. This proportion has been decreasing each decade with a minimum of 3.98% during the 2000s. The reasons for this are a combination of higher reporting for weaker tornadoes and climate change. Many atmospheric scientists argue that as the Earth warms due to climate change, the energy imbalance between the northern and middle latitudes decreases, lowering the energy available for tornadoes. This means that although tornadoes are still possible, the average strength of tornadoes will likely decrease.
This graph indicates that tornado fatalities vary greatly by year, but that the 10 year average of tornado fatalities has mostly decreased over the past 70 years. The 1950s, 1960s, and 1970s, all averaged over 100 tornado fatalities per year, but recent decades have averaged less than 100 tornado fatalities per year, oftentimes even below 60 fatalities a year. The 1950s had the highest average with 142 fatalities per year and the 1980s had the smallest average with 52.2 fatalities per year. We account this due to better tornado modeling, predicting, and warning systems that better prepare people for incoming tornadoes. Additionally, we believe that if everyone had a tornado shelter in their home, that these numbers would decrease even further. This highlights the importance of being prepared for tornadoes and that tornado shelters are extremely important in reducing tornado fatalities.
This map plots the locations of tornadoes that occured in Wisconsin since 2000. As you can see, tornadoes can occur in practically every space of Wisconsin. The majority of these tornadoes are weak (F0, F1, F2), but fourteen F3+ tornadoes have touched-down in Wisconsin over the past 20 years nonetheless (black dots). In total, 576 tornadoes have occured in Wisconsin since 2000 and each one of these had the potential to cause major damage and death. Just because a tornado isn't rated very high doesn't mean that it isn't dangerous. Hopefully, this map convinces all Wisconsin residents to create action plans for if a tornado impacts their community.
Texas, Oklahoma, Kansas, Nebraska, and South Dakota are the states typically considered as part of "Tornado Alley." We wanted to look at whether or not these states actually suffered more in terms of economic damage and loss of human life. These "Tornado Alley" states are displayed in red among the other 45 states in tan. As you can see, each of these states falls on the higher end of the data, but there are states that have sufferered more in these aspects that are not in "Tornado Alley."
This map plots the locations of tornadoes that occured in the United States since 2000. Stronger tornadoes are plotted in darker colors AND with higher alpha values. This allows one to see not only where tornadoes occur in the United States, but also where the most dangerous ones occur. The map shows that the largest threat for devastating tornadoes is throughout the central plains and the south. People who reside in these regions need to have tornado action plans and need to be aware of the risks tornadoes pose. Hopefully, this map demonstrates to the public just how widespread tornadoes are and that they pose a threat to nearly every area of the United States.
With access to data all the way back to 1950, we decided to analyze which states had seen the most tornadoes throughout the decades. Darker colors indicate higher numbers of tornadoes during each particular time period. The overall trend throughout the decades has been an increase in almost every state, with a suprising shift eastward in recent years.