Whilst each flap of a butterfly’s wings does change the air pressure around it, this fluctuation quickly dissipates and is incredibly small in comparison to the large-scale changes in air pressure which determine the weather. Within a few centimetres of a flapping butterfly the disturbance it causes will have been dissipated by the surrounding air molecules, making it difficult to imagine how the minute changes caused by butterfly’s wing flaps could be amplified fast enough to manifestly change the forecasted weather to the degree required to trigger or avert a tornado.