Forty-four tornadoes touched down across Missouri on March 11-12, resulting in 10 fatalities and 107 injuries, according to updated information from ground and aerial surveys done by the National Weather Service’s Missouri offices.
Several of the tornadoes in mid-Missouri, including the one that killed four in Renick, were given an F3 rating on the Fujita scale used to estimate wind speeds based on damage. A tornado in Monroe County was rated F4, a classification for tornadoes with winds between an estimated 210 and 261 miles per hour.
At this time next year, tornadoes causing the same amount of damage will be classified as having lower wind speeds based on research showing the existing scale overestimates wind speed.
The old scale, named after famed storm researcher Tetsuya Theodore Fujita and adopted in 1971, was thought to be limited by meteorologists in its ability to draw a correlation between damage and wind speed.
“The new scale refines the wind speed,” said Pat Slattery, spokesman for the National Weather Service’s regional office in Kansas City. “The corrections will make the enhanced scale ratings more accurate and consistent.”
The new scale will be known as the Enhanced Fujita Scale and will go into effect in February.
Anthony Lupo, associate professor of atmospheric science at MU, said the change will not affect the public, but rather will improve the accuracy and consistency of tornado intensities.
“It is a transparent change as far as the public is concerned,” Lupo said. “But they are going to get a much better picture in the end of how severe a tornado may have hit.”
He said the change will make a bigger difference in Missouri and the Midwest than elsewhere because of its proximity to tornado alley.
The new scale, developed by a forum of meteorologists and wind engineers nationwide in cooperation with Texas Tech University’s Wind Science and Engineering Research Center, will continue to rate tornado categories from F0, the weakest, to F5, the strongest. However, the wind speeds are lowered in every category except F0 to be more accurate by taking into account damage indicators — that is, the type of structures damaged — and the degree of damage to those indicators.
For example, the enhanced scale will differentiate between hardwood and softwood trees as well as buildings such as schools, churches or homes. In the assessment of those structures, eight degrees of damage will be used ranging from visible damage to complete destruction. Field tests and training of the process are under way nationwide.
The National Weather Service is the only agency with the authority to provide an official Fujita scale rating. The rating represents the highest estimated wind speed that occurred during the life cycle of the tornado.