When a twisting funnel drops from the sky with tearing winds of up to 500 km/h, what do you do? In Oklahoma, people thought they knew the answer. The state is in the heart of tornado alley in the US, where the public is regularly drilled on storm awareness. But when the largest storm ever recorded formed on the outskirts of Oklahoma City last year, people ignored the best advice and nearly died in their thousands. Now, officials are nervously watching where the next storm will form - and trying to figure what people will do when it does. Neal Razzell goes out and about with the storm chasers in Oklahoma City.
(Image of a storm brewing over a field. BBC Copyright)