In a talk on Order within Chaos: Big data and weather forecasting, ECMWF Director of Research Erland Kallen and Surrey Mathematics HoD Ian Roulstone join forces at the British Science Festival on Monday 7 September to describe and explain to delegates how weather forecasters identify order over chaos. They will present the latest developments in numerical weather prediction, and place this technology in the context of the widely debated big data phenomenon. We expect the discussion to highlight the basics of numerical weather prediction (NWP), including advances and successes that have marked the past few decades, and the use of observations to define the initial state. Eland Källén and Ian Roulstone’s talk will take place on Monday 7 September, from 17.00 to 18.00. The presentation will be available online after the event.