http://www.sciencedaily.com/releases/2007/08/070830105911.htmThe central and eastern areas of the United States are especially prone to severe storms and thunderstorms that arise when strong updrafts combine with horizontal winds that become stronger at higher altitudes. This combination produces damaging horizontal and vertical winds and is a major source of weather-related casualties. In the warmer climate simulation there is a small class of the most extreme storms with both strong updrafts and strong horizontal winds at higher levels that occur more often, and thus the model suggests that the most violent severe storms and tornadoes may become more common with warming.
The prediction of stronger continental storms and more lightning in a warmer climate is a natural consequence of the tendency of land surfaces to warm more than oceans and for the freezing level to rise with warming to an altitude where lightning-producing updrafts are stronger. These features of global warming are common to all models, but this is the first climate model to explore the ramifications of the warming for thunderstorms.
http://www.sciencedaily.com/releases/2008/06/080602231312.htmBasic thought is there’s more energy in the atmosphere, more water vapor evaporating and greater likelihood for stronger heating events that lead to stronger thunderstorms - super cells, that can lead to tornado production,” Gaffney said.