Why is your forecast ten degrees out?

Like many armchair and amateur meteorologists, I like comparing my expectations with those of the professionals. Just recently, they have not been doing well. In fact, they have done so badly that their reported temperatures have been as much as 10˚C out.

I have of course loaded my dice, stacked the odds against them. For most people, the Isle of Wight is just a mass of coastline, Slartibartfast’s lunchtime doodle, perhaps. But travel just a mile inland, up into our valley nestling among downs, and its climate is often decidedly uncoastal. Down in Ventnor or Shanklin it might be mild and damp, but up here it could be much colder and crisp.

However the Met Office usually offers two locations for forecast and measured temperatures here: Cowes and Ventnor, both a stone’s throw from the sea. A couple of times this week we have been shivering in -5˚C, with a thick crust of ice over much of the outside world, whilst the numbers shown on weather charts read +5˚C – a bit of difference.

Sometimes I pretend that for forecasting purposes we might really be better represented by Bournemouth Airport, Southampton, or even the gloriously-named Middle Wallop. And when we walk up on the downs, we can usually see the first two of them, but never Middle Wallop.

Maybe when the UK Met Office gets its next prodigiously expensive supercomputer fully commissioned, they will be as brave as those in the Norwegian Met Office. The latter not only attempts to produce detailed blow-by-blow forecasts for little hamlets scattered along the many deep valleys throughout Norway, but they even publish their own performance monitor:

Performance bar on the Norwegian Met Office's weather forecasts.
Performance bar on the Norwegian Met Office’s weather forecasts.

Presumably these refreshingly honest measurements are not used for purposes of performance-related pay.