As I sit at my computer tonight and watch reports of tornadoes touching down along the southeast, I have to wonder if Harold Brooks and Victor Gensini might be on to something.
Their paper titled “Spatial trends in United States tornado frequency” has a lot of data that supports a shift of tornado ally toward the east with a decrease in the Plains. If this trend continues, states like Mississippi, Alabama, Arkansas, Missouri, Illinois, Indiana, Tennessee, and Kentucky will see a lot more activity in the future.
I guess time will tell. Regardless we should all be prepared for tornado activity because they can touch down in any state if conditions are right.
A tornado forms when a mesocyclone lowers below a cloud base and begins to take in cool, moist air from the downdraft region of a storm. The convergence of warm air in the updraft and cool air causes a rotating wall cloud to form. Then an area of quickly descending air known as the rear flank downdraft (RFD) focuses the mesocyclone’s base, causing it to draw air from a smaller and smaller area on the ground. As the updraft intensifies, it creates an area of low pressure at the surface. This pulls the focused mesocyclone down, in the form of a visible condensation funnel. As the funnel descends, the RFD also reaches the ground, fanning outward and creating a gust front that can cause severe damage a considerable distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within a few minutes of the RFD reaching the ground.