EMAIL EXCLUSIVE: John Hammond’s Month Ahead Brief cold snap or longer-lasting freeze?!
“Will it snow?”. There’s a lot of nervous excitement out there. But as I’ve been writing in a different blog this week, it can be easy to lose objectivity when one is looking for a certain outcome. It’s called ‘confirmation bias’. Amongst those who like cold and snowy weather, ‘cherry-picking’ of computer forecasts is rife at this time of year, stoked up by the tabloids. And there are currently rich pickings to be had – much chillier weather is indeed on the way, certainly in comparison with recent days. But I wouldn’t dig the sledge out of hibernation just yet. When it comes to snow, next week’s ‘howling’ easterly will be worse than its bite. What happens in subsequent weeks, however, is another matter. The atmosphere is behaving in a peculiar way as December approaches.
Chilly spell arrives
Limited impacts initially
Risk of more severe cold later
MONDAY 19TH NOVEMBER – SUNDAY 25TH NOVEMBER
‘Beast from the East’? Hardly
As we tap into progressively chillier air early in the week, the mercury will fall by 10 degrees or more from the previous week. Blustery winds, cloudier skies and scattered showers will add to the bleak feel, although initially, some western parts of the UK look favoured for the best of the crisp sunshine.
The showers spreading from the east will fall mostly as rain; but some sleet or wet snow is possible in the heavier ones. The higher hills will inevitably be most susceptible, although amounts should generally be trivial. This air is just not cold enough to produce widespread snowfall at this stage, whatever you may read. Where winds fall lighter, overnight frosts will become more widespread; but for much of the time, the gusty easterly will keep temperatures above freezing.
Towards the end of the week, some more prolonged rain may be spinning up from the near Continent and spreading more widely across the UK. However, by the weekend somewhat drier, but still chilly winds will resume.
A fleeting cold snap? Read on…
…our regular diet of mild, maritime air cannot be relied upon to hit and hold
MONDAY 26TH NOVEMBER – SUNDAY 2ND DECEMBER
Strange ‘goings on’ in the Arctic
What happens next will be crucial to whether this is a brief wintry encounter or precursor to a more severe onslaught. The huge ‘buckle’ in the jet stream that is sending chilly easterlies our way is also pumping southerlies deep into the Arctic. Rather like prodding a balloon, this unusual indentation of warmth into polar regions can force cold air to spew outwards on either side.
There is a non-zero chance that through the last week of November, much more intense cold will discharge down through northern Russia and Scandinavia. If this were to occur, the chances of widespread and disruptive snowfall reaching our shores would increase significantly. It’s one to watch.
However, it’s a fool who doesn’t continue to look to the Atlantic. Any incursions of milder air into the southwest will bring the prospect of rain and perhaps transient snowfall. But with such a distorted jet stream across the northern hemisphere, a return to our regular diet of mild, maritime air cannot be relied upon to hit and hold.
I’m keeping an eye on the stratosphere
MONDAY 3RD DECEMBER – SUNDAY 16TH DECEMBER
Seasonal start to Winter
The peculiar configuration of the atmosphere has some parallels with 2010. It’s certainly been seized upon by some ‘cherry pickers’. Extreme cold and snowfall brought the nation to its knees in that record-breaking December; and so could we be about to plunged into a deep and prolonged freeze? Well, there are significant differences in the oceans and atmosphere from eight years ago, and I do not suggest that history is about to repeat itself. The weather doesn’t work like that.
There will be milder incursions. Nevertheless, there are no clear signs of the jet stream readily ironing out its huge meanderings and bringing us reliably back to normal. On balance, then, I expect much of early December to remain on the cold side, with the wintry threats which that bring us. That should help the festive feel at many an upcoming event. Here’s a selection.
All the while, I’m keeping an eye on the stratosphere. The vortex of westerly winds many miles above us has been quite strong of late – seemingly disconnected from the atmospheric distortions we’re seeing closer to earth. However, there are signs that this vortex may slow markedly in the weeks ahead. Slowing is one thing. If it goes into reverse, that’s quite another. That’s how the ‘Beast form the East’ began…
Here’s a reminder of our Early Winter Forecast.
Appetising enough? There may be plenty of other ‘cherries’ out there to choose from, but I wouldn’t necessarily trust their allure