Cold air has returned to put a stop to the warm snap across the eastern United States. That’s the plotted 3 hourly observations for the last week (fig 1) for Albany in New York state. Last Sunday they were reporting temperatures as low as -22.8°C, but a warm snap rapidly warmed things out from Wednesday, and by 00 UTC last night Albany were reporting a 18-00 maximum of 17.2°C, then just 15 hours later the temperature has fallen by 24.4°C as cold air flooded southward, so by 15 UTC this afternoon it was -7.2°C and snowing again. Quite an amazing sequence of rapid warming and cooling. Here’s the thermograph (fig 2).
Any morning cloud that’s been affecting some southern areas has now dissolved away, and it’s a wonderful afternoon across the bulk of the country. It’s still possible to see the extent of the snow over the mountains of Scotland through the thickening frontal cloud (fig 1).
The easterly wind is blowing fresh or strong across southern areas though (fig 2).
This has meant that wind chill has been sub-zero in the more exposed places (fig 3), but not excessively low because of the clear skies and widespread sunshine (fig 4).
You may think that it’s a little bit parky in our neck of the woods, but the real cold air is affecting eastern North America at the moment. In Quebec and Ontario air temperatures as low as -34.8°C have been reported in the 06-12 minimum temperatures of the 12 UTC SYNOPs. This is only half way through the night though across there, so temperatures may well drop even lower than that by the time dawn arrives.
Yesterday afternoon the Met Office were promising the coldest night since February 2012 (fig 1) when they said on Twitter:-
“Temps in rural parts of Scotland could fall as low as -14 or -15 °C tonight, which would make it the UK’s coldest night since 11 February 2012, almost 6 years ago! High pressure will bring clear & calm conditions and is dragging cold arctic air from the north”
Unfortunately, the low cloud of yesterday evening didn’t finally clear till towards midnight, neither was it ever perfectly calm, and with only a patchy or thin cover of snow, the air temperature never got down as low as the -14°C that was promised.
In the end after trawling through all climate reports from sites which they like to keep to themselves, they did manage to find a -9.1°C at Dalwhinnie, just down the A9 from Aviemore (fig 2). The model does have problems, the -9°C instead of -15°C is just a symptom, it mishandled the overnight forecast of low cloud, surface wind, and probably the whole pressure field.
For the rest of us poor mortals who have to rely on the kindness of a man in Barcelona and his OGIMET website, here are the coldest spots from the SYNOP reports (fig 3). As you can see the other forecast temperatures outwith the Highlands of Scotland were much more accurate, except for southern areas and across East Anglia, where the strength of the wind prevented an air frost.
How did the BBC do?
The BBC who presumably use the same model data as the Met Office, almost got it almost right with a -10°C minimum (fig 4). I don’t know what they were thinking with a -4°C for the Western Isles and a -3°C for the Northern Isles though.
At one time the Met Office would have been just content in announcing the coldest night for six years after it had happened. But now because of the pressures of social media and to maintain their corporate image, they feel they must announce it before it does. This faux pas is certainly not on the same scale as the barbecue summer forecast was, and probably will go unnoticed by the vast majority of people anyway.
Just as a reminder a superlative is described by the dictionary in Google as:-
I’ve heard so many reports across social media describing just how cold, very cold, bitter or raw this weekend will be across the country as colder northeasterly air spreads southwestward across the country, that I thought I’d take a look. Here are the forecast temperatures across the country for Sunday (fig 2).
And here are what the mean maximum temperatures for January look like across the UK (fig 3).
So all this incessant hype I’ve heard in social media about the coming change of weather type, and talk of just how cold this weekend will be, should be taken with a pinch of salt, because although it’s turned colder, in reality and for a variety of reasons it’s not that cold at all.
No doubt, the ‘feel like’ or ‘wind-chill’ temperature figures will be brought into play as winds strengthen across southern areas on Sunday, but let’s not get carried away with the fact that these temperature are nothing out of the ordinary for January and put them into perspective.
Here’s a look back at the 12th of January 1987 (fig 4) to see a situation that does merit the superlative ‘bitter’, to describe the coldest and snowiest days spells of weather that I can remember in my lifetime in the British Isles.
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.
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.
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).
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.
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!
If we do see an easterly anticyclonic spell in the next few weeks the temperatures may not be as cold as usual in the UK, because the source of that cold continental air has been very mild throughout this autumn and early winter. At the moment Moscow isn’t reporting a snow depth, because there isn’t any, which in itself is uncommon at the turn of the year (fig 1), in fact the mean temperature there has been anomalously warm since the start of November. The chart of snow and ice cover for the northern hemisphere (fig 2) illustrates the lack of snow. In the last twenty years a chart similar to this one has become a common feature of many a winter.
Here are the anomalies so far this month for our part of the northern hemisphere, as you can see there is a large positive +5°C anomaly across western Russia, so it’s no wonder there’s not much snow in Moscow (fig 3).