Because tornadoes sometimes go undercounted, especially in the past and in less populous areas, scientists don’t like to study trends by using counts of tornadoes. Gensini and tornado scientist Harold Brooks of the National Severe Storms Lab looked at “significant tornado parameters,” a measurement of the key ingredients of tornado conditions. It looks at differences between wind speed and direction at different altitudes, how unstable the air is and humidity. The more of those three ingredients, the more likely tornadoes will form.