What’s an EFU tornado? How did it get that name and how common is it in Kansas?

National Weather Service officials received reports and photos that convinced them a brief, early-evening tornado had touched down on June 28 of last year east of Interstate 335 in Lyon County.

They estimated the twister was 30 feet wide and stayed on the ground 2.37 miles while passing largely over open country.

But no damage could be found.

The weather service consequently gave that twister a rating of “EFU” on the Enhanced Fujita scale used to measure tornado intensity, its records show.

What is an EFU tornado?

EFU tornadoes are those for which intensity can’t be determined because they leave no damage for the weather service to survey, with the “U” standing for “unknown,” according to the website for The Weather Channel.

The EFU rating existed before 2013 but wasn’t put into practice until 2016, that site said.

EFU tornadoes tend to be most common on the plains or in Midwest states because fewer trees and structures are present there for such twisters to damage, it said.

Weather service records indicate 2019 was the year the weather service began applying the EFU rating to tornadoes in Kansas.

Where do EFU tornadoes fit on the Enhanced Fujita scale?

The introduction of the EFU rating was part of a process that began when Ted Fujita, of the University of Chicago, in 1971 introduced the Fujita Scale, which rates tornado intensity based primarily on the amount of damage.

That scale was replaced in February 2007 in the U.S. by the Enhanced Fujita Scale, which in its initial form rated tornado severity on levels ranging from EF0 to EF5.

Wind speeds range from 65 to 85 mph for an EF0 tornado, 86 to 110 mph for an EF1, 111 to 135 mph for an EF2, 136 to 165 mph for an EF3, 166 to 200 mph for an EF4 and more than 200 mph for an EF5.

The first EF5 tornado recorded in Kansas struck in May 2007 at Greensburg in the south-central part of the state, staying on the ground for 26 miles while killing 11 people and injuring 63.

How common were EFU tornadoes last year in Kansas?

EFU was actually the most common rating last year for Kansas tornadoes, according to weather service records posted online.

Ratings in 2024 saw the following number of tornadoes in Kansas:

• EFU: 29.
• EFO: 26.
• EF1: 13.
• EF2: 7.
• EF3: 1.

Last year’s lone EF3 tornado touched down on April 30, 2024, at Westmoreland, a city of roughly 740 people located about 60 miles northwest of Topeka in Pottawatomie County.

A woman was killed, bringing the state its first tornado fatality since 2012, and three people suffered minor injuries.