Powerful tornadoes impact southern USA (Credit: vance.af.mil)

Powerful tornadoes swept through the Southern U.S. States of Tennessee, Arkansas, Kentucky, Mississippi and Alabama. The storms, which hit Tuesday afternoon and Wednesday morning, are the worst ones to strike the area over the last decade.

Experts estimate that the affected regions were hit by at least 30-40 tornadoes. While winter tornadoes are common, tornadoes with this intensity are rare and this batch the worst since 1999 is thought to be the result of unseasonably warm temperatures in the area.

Despite the fact that there was ample warning, the tornadoes came so fast and were so severe, that over 50 people died. Thousands of homes and businesses were reduced to rubble. While a lot of residents have lost their homes and neighborhoods, they are thankful to be alive and are looking forward to re-building their lives as soon as they can.

WHAT ARE TORNADOES AND HOW ARE THEY FORMED

Toranadoes form only during very severe thunderstorms (Credit: Paul Markowski, Penn State University)

A tornado is a very powerful rotating column of air that starts from the bottom of a thunderstorm cloud and extends all the way down to the earth. A tornado is formed only in very severe thunderstorms called supercells, which lasts much longer than regular thunderstorms. These severe thunderstorms occur when cold dry polar air meets warm moist tropical air. As the warm air rises, winds around the storm cause it to rotate and form a funnel. The air in the funnel spins faster and faster, creating a low-pressure area, which sucks in even more air and sometimes even objects.

While tornadoes' happen in all parts of the World, the U.S. gets the most, about 1000 a year. The worst hit area is a stretch of land in the Great Plains from Texas to South Dakota, known as "Tornado Alley". This area experiences extremely hot temperatures, which cause heavy thunderstorms that eventually lead to tornadoes.

Resources: Wikipedia.org, CNN.com