Could someone who speaks fluent bull***t translate this for me please?
Presumably they all want to know what the weather is going to be.
When designing anything that needs to convey a message it's critical to understand who your audience is. "Just tell them the weather" isn't very helpful. How does your nan want to consume the content? How does her grandson? What makes BBC weather unique and distinctive across the platforms?
They need to determine the design approaches that are both clear and engaging across an audience base that has a hugely diverse age range / digital literacy / understanding of meteorological concepts / love of TV presentation
Creating 'personas' allows them to define a set of characteristics that they will design against.
Weather is complex. People are complex. The methods of delivering the content is complex. Designing information systems that work for everyone is incredibly difficult, good design doesn't come from thin air and it certainly doesn't come from a brief consisting of "just tell me the weather mate".
This is not Perfect Curve, it's design 101