According to the United States Drought Monitor, two-thirds of the nation is covered by a drought that stretches from coast to coast. Federal officials recently designated 23 Wisconsin counties as natural disaster areas. The drought is so bad that some people are even painting their lawns green, which raises a whole separate set of environmental questions.
But there’s at least one upside to this devastating drought: a near-record low number of tornados. According to Harold Brooks, a tornado expert at the National Severe Storms Laboratory, the weather needed to form tornados has been in short supply this summer—and drought conditions are a key reason why.
The high pressure over the Central U.S. has brought stifling heat and much-below average rainfall to a broad swath of the country.
But Andrew Freedman from Climate Central says in order for tornadoes to form, there also needs to be high humidity, strong jet stream winds, and winds that change direction or speed with height, known as wind shear. He says these ingredients haven’t come together in the right amounts, at the right time this summer.
Dry ground discourages storms by releasing less moisture into the air. The jet stream has stayed to the north, depriving thunderstorms of the wind shear needed to form large hail and tornadoes.
The lowest number of tornadoes in any year occurred in 1988, which was also a drought year. While Brooks says he doesn’t expect this record to fall, he adds that “we could be the second-lowest without much trouble.”
Despite all the drought’s devastation this year, the low twister count is one, small silver lining.
Web Links
http://droughtmonitor.unl.edu/
http://www.huffingtonpost.com/2012/07/26/wisconsin–drought-2012-disaster–areas_n_1705556.html
http://www.huffingtonpost.com/2012/07/28/tornado–season-2012-recor_n_1711679.html?utm_hp_ref=green
Photo, taken on July 24, 2012, courtesy of CraneStation via Flickr.