Tornado Temporal Climatology

The amount of observed tornadoes has increased over the years. As can be seen by the black trend line in the graph below (Figure 1), the frequency of tornadoes being recorded was increased from the early 60s. This can be explained in part by the widespread use of observation technology, such as doppler radar, with modern times.

Figure 1: Tornado tracks of confirmed tornadoes from 1961 - 1990

Tornados are a byproduct of severe thunderstorms. Thunderstorms are fueled by warm, unstable air at the earth's surface. It is reasonable to expect that the most thunderstorms, and therefore the most tornadoes, will occur in the late afternoon where the sun has heated the surface air to its maximum extent. The graph below (Figure 2) shows the frequency of tornadoes as a function of the time of day. The graph clearly shows that tornados are most common in the later afternoon and early evening hours.

Figure 2: Tornado tracks of confirmed tornadoes from 1961 - 1990