Wednesday 8 March 2017

Hundreds of homes damaged as storms sweep across America's Midwest.

Hundreds of homes have been destroyed an a number of people have been injured as series of storms swept across the American Midwest on Monday 6 March 2017. The worst of the damage occurred around Oak Grove on the border between Jackson and Lafayette counties in Missouri where about 500 homes and commercial buildings were damaged or destroyed by a tornado that reached three on the Enhanced Fujita scale (or an EF-3 tornado), with winds peaking at 245 km per hour. 

The aftermath of the 6 March 2017 Oak Grove tornado outbreak. Kansas City News and Weather.

Elsewhere in Missouri between fifty and sixty homes were damaged or destroyed by an EF-2 tornado with peak winds of over 210 kilometres per hour in Smithville. 46 homes were damaged in the Kansas City suburb of Leaward, while twelve aircraft hangers were damaged and one destroyed at Johnson County Executive Airport. Two people were injured and a number of properties were damaged after an EF-1 tornado with winds of 140-175 kilometres per hour hit Wentzville. A water treatment plant was damaged in Odessa and tornadoes were also reported in Lee's Summit and Macks Creek.

 Overtuned mobile home in Wentzville, Missouri following the 7 March 2017 tornado outbreak. Robert Cohen/St Louis Post-Dispatch.

In Iowa an EF-2 tornado with winds peaking at 185 kilometres per hour hit the city of Muscatine leaving a trail of destruction 200 m wide and over three kilometres in length, with three people injured and over eighty homes damaged. A second tornado hit the city of Blue Grass, though this caused only minor damage. Tornadoes were also reported in Minnesota, the earliest in the year ever reported in the state, as well as in Kansas and Illinois, while major thunderstorms were reported in Louisiana, Mississippi and Alabama.

 Damage in Seymour, Iowa, following the 7 March 2017 tornado outbreak. Daily Iowegian.

Tornadoes are formed by winds within large thunder storms called super cells. Supercells are large masses of warm water-laden air formed by hot weather over the sea, when they encounter winds at high altitudes the air within them begins to rotate. The air pressure will drop within these zones of rotation, causing the air within them so rise, sucking the air beneath them up into the storm, this creates a zone of rotating rising air that appears to extend downwards as it grows; when it hits the ground it is called a tornado. 

Tornadoes can occur anywhere in the world, but are most common, and most severe, in the area of the American mid-west known as 'Tornado Ally', running from Texas to Minnisota, which is fuelled by moist air currents from over the warm enclosed waters of the Gulf of Mexico interacting with cool fast moving jet stream winds from the Rocky Mountains. Many climatologists are concerned that rising temperatures over the Gulf of Mexico will lead to more frequent and more severe tornado events.

Simplified diagram of the air currents that contribute to tornado formation in Tornado Alley. Dan Craggs/Wikimedia Commons/NOAA.

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