Insider Blog: First EF-5 tornado since 2013 recorded in North Dakota following months-long survey

The National Weather Service on Monday released a new report confirming the first EF-5 tornado since May 2013.

The tornado, initially rated an EF-3, hit near Enderlin, North Dakota on June 20, killing three people and derailing a train in the process. The tornado was on the ground for around 20 minutes and was about one mile wide at its strongest.

After multiple surveys, wind engineers from across the country and Canada made the upgrade after investigating full grain hopper cars that were moved and tipped over off the railroad tracks. An empty tanker car was thrown 475 feet away from the tracks.

Meteorologists also observed a farmhouse swept clean from its foundation and debarked trees. All of these areas of damage were scored by comparing damage indicators to the Enhanced Fujita or EF-Scale which measures the strength of a tornado by its wind speed and degree of damage.

The Enderlin tornado was determined to have maximum winds between 200-210 mph by confirming those damage indicators and comparing them to wind velocity data from nearby National Weather Service radar.

The EF-Scale goes from weakest, EF-0 with winds up to 85 mph, to strongest, EF-5 with winds greater than 200 mph.

The last EF-5 tornado to hit the U.S. was recorded on May 20, 2013 when a mile wide monster carved a path through Moore, Oklahoma, killing 24. That tornado notoriously hit two elementary schools in the late afternoon as it traveled 14 miles through the city.

The last EF-5 to strike Missouri hit Joplin in May 22, 2011, killing 158 people on a Sunday evening. The Joplin EF-5 still stands as the 7th deadliest tornado in U.S. history.

Many violent tornadoes have struck since 2013, but for a tornado to be rated according to the EF-Scale, it must hit objects that can be categorized through damage indicators along with radar velocity data.