Overnight ice in southwest poorly forecast

Figure 1 – Courtesy of BBC Spotlight (6.55PM)

Here’s the forecast 04 UTC temperatures from the BBC (fig 1) in what constitutes the overnight minimum chart from yesterday evening’s news. As you can see the model colour contoured NWP temperatures have been totally ignored, and labels for much warmer temperatures of “towns and cities” overlaid on top. To me this is totally misleading to any viewer, but the BBC weather presenters continually to do this, ignoring the fact that Exeter airport is one of top UK cold spots, and last night it caught them out again (fig 2), with temperatures dipping to -3.5°C. Even sites closer to the sea such as Plymouth and Culdrose saw a slight touch of frost – their first of the Autumn or Winter.

Figure 2

Unusually the Met Office did respond with a very belated yellow warning of ice for the southwest at 0637 UTC (fig 3), no doubt when they heard about some road accident caused by the rain from yesterday’s showers freezing on roads across Devon and Cornwall.

Figure 3 – Courtesy of the Met Office

There was really no excuse for the lateness of this warning, especially when the Met Office HQ lies just a mile or so west of the airport. They obviously have to follow a process to cover themselves from any possible repercussions from accidents and injuries caused by icy roads and pavements, the only problem is that it came at least 12 hours too late! Temperatures at the airport were already -2°C at 23 UTC yesterday evening so there really was little excuse (fig 4).

Figure 4

They didn’t do too well in the National forecast either, although Darren Bett did say that “cloud might be a bit more unreliable in central areas and that there might be a touch of frost” there (fig 5). I’m not sure if the -3.6° C at Pershore can be regarded as a “touch of frost” though.

Figure 5 courtesy of the BBC (6.30PM)
What went wrong?

I think that the Met Office model, especially across the southwest, just kept producing too much in the way of cloud and showers for much of the night (fig 6) which just didn’t materialise, from looking at the weather radar. I would love to grab some forecast NWP evidence from the UKMO mesoscale model to back that up, but of course that’s on a need-to-know basis, and I don’t need to know!

Figure 6 – Courtesy of BBC Spotlight (6.55PM)

Author: xmetman

An ex-metman passionate about all things to do with weather, climate and clouds

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