BBC: On Tuesday, officials at the US National Weather Service (NWS) upgraded the intensity of Monday's tornado in Moore, Oklahoma from its preliminary estimate of EF4 to EF5 - the top of the scale. But what does that mean?
At its simplest, the highest level of the "Enhanced Fujita scale" indicates the highest wind speeds - greater than 320 km/h (200mph).
Unlike the rest of the scale, EF5 has no upper limit. The NWS report suggests estimated peak winds just into the EF5 regime - far lower than another...