Do tornadoes get the weekend off? A team of researchers from the Department of Marine, Earth and Atmospheric Sciences says no.
Daniel Rosenfeld, a researcher from the Hebrew University of Jerusalem, and Thomas Bell, a researcher at NASA’s Goddard Space Flight Center, originally made the published reports that tornadoes take the weekend off after noticing patterns in storm activity. Together they wrote a paper titled “Why do tornadoes and hailstorms rest on weekends?” Their assertion was that the increased use of aerosol products during the workweek played an intricate role in the formation of tornadoes.
A recent study conducted by N.C. State professors Sandra Yuter and Matt Parker, and postdoctoral researcher Matthew Miller, disproved this claim.
Aerosol is found in a variety of everyday products such as hairspray, foaming cleaners, deodorants and cooking oils. Aerosol pollution may also be attributed to the burning of fossil fuels.
Rosenfeld and Bell said large amounts of aerosol delay the formation of raindrops in clouds. According to the study, delay of raindrops affects air temperature and increases the possibility of tornado formation.
“It’s been widely known for a while that there are weekly cycles in aerosol use,” Miller said. “Much more is used during the workweek than on the weekends.”
According to Miller, the location of the study affects the amount of aerosol use and that the amounts of aerosol released into the atmosphere will vary depending on the area in question.
Yuter, Parker and Miller were able to show that the areas of increased aerosol pollution were not in fact common areas for the formation of tornadoes.
“It is unlikely that the aerosol pollution would impact the so called ‘Tornado Alley’ considering that the pollution is occurring in more eastern locations,” Miller said. “The different concentrations of naturally occurring aerosol versus manmade should be considered.”
Despite the known cycle of aerosol use, N.C. State researchers saw that their data did not support the claim for a weekly tornado cycle.
“Another thing that they looked for was the time period,” Miller said. “If you change the time period you look at, the results will differ. They looked at 1994 to 2009. We looked at an alternate time period and found out that the weekly pattern of tornadoes varied depending on how you processed the data.”
The N.C. State team looked at tornado data from the past 48 years and, while there is variation of how many tornadoes were formed on any random day, there was no clear pattern to suggest that tornadoes “take the weekend off.”
“When we read their hypothesis we saw that it was in [contrast] to our experience in working with tornadoes,” Miller said. “One of the biggest problems was how they processed the data. They only looked at tornadoes for June, July and August while most tornadoes occur in the two months preceding that.”
Yuter, Parker and Miller concluded that the storm systems capable of producing a tornado are capable of winds speeds high enough to delay the formation of precipitation regardless of the amounts of aerosol in the atmosphere.
“The different concentrations of naturally occurring aerosol versus manmade should be considered,” Miller said. “We’ve seen no consistent evidence that aerosol affects tornado formation.”
