Why is the US Getting Even More Damaging Tornadoes?

“The strongest thunderstorms, the strongest severe storms and tornadoes are likely to happen more often and be stronger.” So said Tony Del Genio, a NASA research scientist in a study published in 2007. A unique combination of geography and weather patterns already makes the USA the world’s hottest spot for tornadoes and severe storms in spring and summer. The large land mass that warms on hot days, the contours of the atmosphere’s jet stream, the wind coming off the Rocky Mountains and warm moist air coming up from the Gulf of Mexico all combine.

By Doyle Rice, USA TODAY (29 April 2011):

A massive tornado moves through Tuscaloosa, Alabama. Two separate studies in 2007 reported that global warming could bring a dramatic increase in the frequency of weather conditions that feed severe thunderstorms and tornadoes by the end of the 21st century.

With any major weather disaster these days — from floods and hurricanes to wildfires and this week’s tornado outbreak in the South — people ask questions about its relation to the huge elephant that’s lurking in the corner, global climate change.

Two separate studies in 2007 reported that global warming could bring a dramatic increase in the frequency of weather conditions that feed severe thunderstorms and tornadoes by the end of the 21st century.

One study, in the Proceedings of the National Academy of Sciences, found that locations could see as much as a 100% increase in the number of days that favor severe thunderstorms.

“The densely populated regions of the South and East, including New York City and Atlanta, could be especially hard-hit,” reported study lead author Jeff Trapp of Purdue University.

The fuel for the more intense storms would be the predicted warming of the Earth caused by the burning of fossil fuels that release greenhouse gases.

Although the typically stormy spring could see more storms, “summer should have the highest increases in severe weather,” said Trapp. His team reported that by the end of the century, the number of spring days with severe thunderstorm conditions would increase mostly over the Southern Plains and Florida.

But in the summer, almost the entire eastern half of the country might see an increase in days conducive to more severe storms, with the largest increases likely near the Gulf of Mexico and the Atlantic coast.

In the other study, lead author Tony Del Genio, a NASA research scientist, said the basic ingredients for whopper U.S. inland storms are likely to be more plentiful in a warmer, moister world.

“The strongest thunderstorms, the strongest severe storms and tornadoes are likely to happen more often and be stronger,” Del Genio said when the study was published.

With a computer model, Del Genio looked at the forces that combine to make thunderstorms.

A unique combination of geography and weather patterns already makes the USA the world’s hottest spot for tornadoes and severe storms in spring and summer. The large land mass that warms on hot days, the contours of the atmosphere’s jet stream, the wind coming off the Rocky Mountains and warm moist air coming up from the Gulf of Mexico all combine.

Del Genio’s computer model shows global warming will mean more strong updrafts, when the wind moves up and down instead of sideways.

The paper he co-authored appeared in the journal Geophysical Research Letters.

Source: www.content.usatoday.com