12 February 2018

The BBC’s New 14 day Weather Forecasts Are Bollocks

Posted by Dan Satterfield

I have no problem with the BBC dropping the UK Met office for their forecasting and going with a private company. and their new on-air weather graphics are actually quite good.

HOWEVER

Their new 14-day deterministic weathercasts are (in terms the average UK bloke will readily understand) bollocks.

The BBC are also giving hourly forecasts out to 14 days when statistical skill scores show that even a maximum temperature forecast has little skill.

Make no mistake, forecasts are getting better and better. A report (a few years back) estimated that reliable forecasts are increasing by about a day per decade and this seems subjectively right to me. So, the question here is how far out can a reliable forecast go as of 2018? The answer is pretty easy. Look at forecast verification and the skill scores on numerical models.

The skill scores beyond ten days for the ECMWF model (considered the best long-range model by most everyone) show skill falling apart rapidly beyond 7 days.

The answer is about 5-7 days most of the time. Ten days is really pushing it, but there is some skill with a general (warmer/colder/drier) forecast. Forecasting a high of 7° C and a low of 2° with a 30% chance of precipitation 14 days out with a skill that exceeds climatology is not possible. The BBC is not only doing that, but they are posting an HOURLY forecast out to 14 days.

Poppycock. 

If the company providing the BBC with weather services has data that says they can beat climatology at 14 days, I’m all ears and will eat my words. Around the world, there is no better news organization than the BBC. They are indeed the gold standard and that is why this matters. This is a nick on their reputation that’s needlessly inflicted, so here’s a suggestion: Talk to the Royal Meteorological Society and get their opinion on how far out they should push their forecasts. If that is not good enough, ask the Royal Society to do a study on it. I am quite confident that it will NOT be anywhere near 14 days.