“Quad-State Tornado” crossed four states in four hours, a rare December tornado

Since 1950, there have been only 19 F / EF4 tornadoes in the United States in the last month of the year and only 2 F / EF5 tornadoes.

The last EF4 tornado to hit the United States in December was during the Christmas outbreak of December 2015.

The last EF5 tornado to hit the United States in December was in 1957.

An EF5 tornado is the strongest designation a tornado can receive. Exceptionally rare, these tornadoes can produce wind speeds in excess of 200 mph. The last EF5 tornado to hit the United States was Moore, Oklahoma, in May 2013. It was 3,125 days ago and the longest streak on record.

This event was caused by a volatile atmospheric configuration that was poised to produce violent, long-trajectory tornadoes. Exceptionally warm and record-breaking temperatures for the season on Friday looked more like spring than mid-December. This heat, combined with high humidity, provided enough fuel for the storms.

A woman searches for valuables among the remains of a house on December 11, 2021 on the F Freeway in Defiance, Missouri.Christian Gooden / St. Louis Post-Dispatch via AP

As the day progressed, the wind fields strengthened, helping to create the momentum, or “spin”, in the atmosphere needed to produce tornadoes.

A cold front crossing the region triggered the storms, which, with all the ingredients in place, created the right conditions for a tornado outbreak.

Adding to the favorable atmospheric ingredients is the fact that the United States is currently in a La Niña model, which historically increases the frequency of tornadoes in the Mississippi Valley.

And climate change may also have played a role.

Research reveals that climate change can cause tornado alley to shift eastward, out of the traditional Great Plains tornado alley, and into parts of the Mississippi Valley.

Local residents walk past the scene of a train derailment after a devastating outbreak of tornadoes ravaged several states in Earlington, Ky. On December 11, 2021.Cheney Orr / Reuters

While meteorologists and climatologists cannot yet say that the frequency of tornadoes is increasing around the world Due to climate change, it can be said with relative certainty that the frequency of tornadoes and the associated vulnerability are increasing for the Mississippi Valley and parts of the Midwestern United States.

Kentucky Governor Andy Beshear described the tornado as the most devastating to hit the state, estimating that it could have killed at least 70 people or more than 100.

This will make this event not only one of the deadliest tornado events in Kentucky history, but also in U.S. history, and potentially the deadliest December outbreak on record.

Nighttime tornadoes are twice as likely to cause fatalities as their daytime counterparts. This is because tornadoes are harder to see at night and people who sleep often have no way of being awakened when warnings are issued.