The recent outbreak of large and destructive tornadoes in the mid-west has a lot of folks speculating climate change is the cause, but caution must be taken before making such correlations. Although the average number of tornadoes reported each year has in fact increased, this does not mean there are any more tornadoes now than in years past. That may sound contradictory, but a lot has changed in recent years that allows meteorologists to better detect and categorize tornadoes.
There have been great technological advancements in tornado detection in recent years. Sophisticated NEXRAD (Doppler) Radar and its software is far more sensitive now than ever before and as a result, can detect the smaller EF-0 tornadoes that would have otherwise gone undetected. In years past, if the tornado wasn’t spotted by a trained observer in the field, it wasn’t counted due to the inability of the radar to detect them. Furthermore, there are more of these advanced radar systems deployed throughout the mid-west, increasing the coverage area.
The other reason for an increase in detection has to do with the number of people who chase and observe such storms. There has been a recent craze amongst weather enthusiasts to seek out these large storms, not only for fun, but for profit. In some cases, the media will pay a fair amount of money for video of these storms, especially the larger ones that cause more damage. If storm chasers are in remote areas chasing large storms, there is a greater likelihood of a tornado being spotted and thus reported.
Another reason has to do with the number of people who have smartphones that can take pictures and video. Even an untrained person who wasn’t actively pursuing the storm can document a tornado and provide sufficient evidence that one in fact touched down. This is especially true of small tornadoes that may only exist for a matter of seconds and would have otherwise never been detected by radar or spotted by trained personnel.
Lastly, “Even if a tornado is not actually observed, modern damage assessments by NWS personnel can discern if a tornado caused the damage, and if so, how strong the tornado may have been” (Source: NOAA) That is to say, if no one saw it, that doesn’t mean it didn’t occur. Based on the type of damage, trained personnel can determine whether a tornado caused the damage or if it was some other event such as a microburst, thus increasing the count.
These new detection methods skew the trend of how many tornadoes were reported, as compared to many years ago. So the question ‘Are there more tornadoes now than before‘ is a question that will be answered, but only in time after more data is collected and assuming there is no change in the current observation methods.
What about the larger tornadoes? Are there more of them?
Based on historical data, this does not appear to be the case. In looking at the official National Weather Service data starting in 1954 (see graph on left), it would appear the number of strong tornadoes rated EF3 or greater has experienced a slight decline in their trend over the last 60 years, with major spikes occurring in 1974, 1957, 1965, and 2011.
This may seem contrary to what you’ve heard and seen on TV, because folks in the mid-west have suffered through some large tornadoes in 2013. But again, caution must be exercised. The media is incredibly powerful and persuasive, even when they don’t mean to be. If in one year there were three EF5 tornadoes that touched down in remote areas which caused no damage, the news may not report on them and very few people would ever know they occurred. However, if in the next year three EF5 tornadoes ripped through a large city, causing major damage, it would be all over the news and would make one think this is not normal. Well, it would be normal for there to be three EF5 tornadoes, but perhaps it wouldn’t be normal for them to hit a large city. However, that’s just a matter of odds and not occurrence.