Three Tornadoes From Saturday Were Rated EFU; Here's What That Means

Chris Dolce

Published: March 31, 2020

The red icons show the approximate locations of Saturday's three EFU tornadoes.

Three tornadoes from Saturday's severe weather outbreak in the Midwest were not assigned a rating by the National Weather Service (NWS) because they briefly touched down in rural locations and there was no evidence of damage.

Tornadoes are typically rated from EF0 (light damage) to EF5 (catastrophic damage) on the Enhanced Fujita Scale based on the damage that they cause, not by their appearance or any other real-time metric. But when a tornado strikes a mostly rural area with few structures or trees, the damage may be so sparse it can be difficult for the NWS to estimate the strength of the winds.

When there is no tornado damage but there is evidence a tornado existed, the NWS can give an EFU rating for "unknown" to be used in official records. Two tornadoes in Iowa and one in Illinois from Saturday matched the criteria to be rated EFU.

The tornado in Illinois was located southeast of the Quad Cities and was confirmed based on storm spotter and photo evidence. It was on the ground for about one minute and 1.1 mile.

Iowa's two EFU tornadoes were located between Des Moines and Waterloo. They both lasted a minute and tracked for 0.8 miles and 1 mile, respectively.

NWS Des Moines

✔@NWSDesMoines

Preliminary rating on the tornado south of Hudson on 3/28/2020 is an EF-Unknown. When a tornado does not strike a damage indicator (electric pole, out building, etc), the rating is listed as unknown. #iawx

8

8:49 AM - Mar 30, 2020

Twitter Ads info and privacy

See NWS Des Moines's other Tweets

There were nearly 200 tornadoes rated EFU in 2019, according to NOAA's Storm Events Database. Many of them were in Plains or Midwest states where there are fewer structures and trees for tornadoes to hit and cause damage that can be rated by an NWS survey team.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.