Strong/Violent tornado statistics

[STurner]

I have noticed over the past 10 or so years that strong/violent tornadoes have decreased. On the original fujita scale F3 tornadoes made up about 6% of all tornadoes, F4 tornadoes made up 2% of all tornadoes, and F5 tornadoes made up about 1% of all tornadoes. These numbers decreased about 5-10 years ago on the original fujita scale to F3 tornadoes being about 4% of all tornadoes, F4 tornadoes being less than 1% of all tornadoes, and F5 tornadoes being less than .1% of all tornadoes. On the EF-scale EF3, EF4, and EF5 tornadoes account for less than 4% of all tornadoes. There have also been recent years where F4/EF4 and F5/EF5 tornadoes have made up for less than .5% of all tornadoes in that particular year. Could this be because some tornadoes in the past were missed or some of these tornadoes may have been incorrectly rated because the construction may have not been of good quality. Also does anybody know when the strong/violent tornadoes decreased statistically.

 

[Jim Tang]

Strong/violent tornadoes haven't really decreased; rather, the number of non-strong/violent tornadoes have increased with the advent of Doppler radar technology and a better nationwide spotter network. Because the total number of tornadoes have increased, the ratio of strong/violent to total tornadoes have decreased.

 

[Jason Foster]

Additionally, there may be climatological variations. Jim is absolutely right about the reporting aspect which likely makes up the majority of the change. However, because F4 and F5 (old scale) events are rare, and their numbers fluxuate, they can cause a greater shift on a percentage (ratio) basis. I am sure at some point the true number of tornadoes will be very close the the actual number of confirmed reports. At that point we should start to get a better data set (as well as the addition of more and more years) that means we can get better modeling and statistical data that more accurately predicts patterns (if any) in the tornadic seasons and the resulting numbers, frequency, locations, etc.