How the Oklahoma tornado was formed

Help

At least 91 people, including 20 children, are feared killed by a huge tornado which tore through Oklahoma City suburbs, officials in the US state say.

Worst hit was Moore, south of the city, where neighbourhoods were flattened and schools destroyed by winds of up to 200mph (320km/h).

BBC weather presenter Ben Rich explains how the tornado was formed.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.