17 other tornado tracks identified in the December 15 derecho; total is 61


CEDAR RAPIDS, Iowa (KCRG) – The total number of tornadoes discovered during an outbreak in mid-December continues to add up, based on new data from the National Weather Service.

Ongoing damage trace studies, using in-person examinations and satellite data, by the National Weather Service offices in Des Moines, Omaha, Sioux Fallas and La Crosse, have located traces of 17 additional tornadoes since. the last major update a week after the storms swept through Iowa. While the outbreak was already the most prolific in Iowa history, that puts it at more than twice as much as the previous record holder.

A list of the days with the most tornadoes in Iowa history, according to the National Weather Service.(KCRG)

Most of the tornadoes occurred in central and western Iowa, although a total of 10 tracks were identified in counties within the KCRG-TV9 viewing area. That’s an increase of three since the last updates. Five roads traversed parts of Franklin County, two in Hardin County, two in Floyd County, three in Howard County, and one in Chickasaw County.

Fujita’s improved ratings, which are based on tornado damage surveys, now stand at 11 EF-0 ratings, 23 EF-1 ratings, and 21 EF-2 ratings. Six tornadoes did not produce enough damage along their path to receive a damage score, and instead received the EF-U label for “unknown.”

An updated map of confirmed tornado tracks from a severe weather outbreak on December 15, 2021.(KCRG / tracks via national weather service)

The 21 tornadoes to rate EF-2 also make it a record for the number of tornadoes of this force, or more, in a single day in Iowa. The previous record was 16 on June 7, 1984. Iowa averages only 6.25 tornadoes per year of force EF-2 or greater.

Iowa averages about 48 tornadoes per year, based on data between 1980 and 2019. During the same period, only 4 tornadoes occurred in the month of December, making this particular storm not just an outlier. for any time of year, but an extreme anomaly for December. June and May, in that order, represent the most tornadoes in the state in an average year.

Prior to that December outbreak, 51 tornadoes had been confirmed by the state’s National Weather Service for 2021, meaning the total for the year to date is 101.

The highest number of tornadoes in a month in the state was 57 in May 2004, so the current number for December 2021 is now the record holder for the most tornadoes in a month in the record l ‘Iowa.

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