Beyond the Barometer: National Weather Service La Crosse to adopt EF-U tornado rating

MADISON, Wis. -- Starting immediately, the National Weather Service La Crosse office will adopt the EF-U (Unknown) rating as an acceptable rating for tornadoes that touch down in parts of Wisconsin, Iowa and Minnesota.

Making up less than 5% of all tornado touchdowns in the United States, according to the Storm Prediction Center, an EF-U (Unknown) rating is given to tornadoes with no surveyable damage. The EF-U rating may be due to the damage survey crew's inability to reach the path of the tornado, there are no damage indicators or damage from one tornado can't be differentiated from damage caused by another tornado.

Developed by Ted Fujita with the help of Allen Pearson, the Fujita Scale was introduced in 1971 as a way to rate tornadoes based on the damage left behind. Called the Fujita Scale, the rating system began rating tornadoes beginning in the late 1970s as well as retroactively rated tornadoes through the 1950s.

The Fujita Scale rated tornadoes as either F0, F1, F2, F3, F4 or F5 where F5 is the strongest tornado with estimated winds between 261 - 318 mph.

In 2007, the Fujita Scale was replaced by the Enhanced Fujita Scale, which more accurately rated tornadoes. This assessment is based on taking into account more vegetation and possible structures, along with how different structures are built and added more degrees in which damage is assessed.

Like the Fujita Scale, the Enhanced Fujita Scale initially rated tornadoes on a scale from EF 0-5 where EF 5 is the strongest tornado with estimated winds at or greater than 200 mph.

In July of 2018 , the National Weather Service added the EF-U (Unknown) rating to the Enhanced Fujita Scale, along with a set of criteria for a tornado to be rated EF-U. This includes an explanation as to why the tornado was not given a rating.

Since 2014, Wisconsin has recorded only 2 EF-U tornadoes, both touching down in 2023. The first EF-U touched down in Walworth County while the second EF-U tornado touched down near Belleville in Green County.

In 2024, Wisconsin has reported no EF-U tornadoes despite 42 tornadoes touching down across the state. At 42 reported tornado touch downs, 2024 is Wisconsin's fourth most active year for tornadoes, following closely behind 1980 which had a total of 43 touch downs. 2010 had 46 touch downs while 2005 had the most, with 62 tornadoes touching down in Wisconsin during a single year.

During a tornado warning, the safest place you can be is in either a basement or in the most interior room on the lowest level of the building. If you are outside, the safest place to be is laying flat on the ground.

During severe weather, make sure to stay with News 3 Now the for the latest severe weather coverage and download the News 3 Now First Warn Weather app to receive weather alerts.

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