John gives us his latest thoughts on likely weather trends over the next few weeks. To ensure you are reading the very latest weekly blog, check out our Wow and Why page here
As I mentioned in my last blog, longer term predictions are made especially difficult when the atmospherics across the northern hemisphere are as they currently are. Bulges of warm and cold are being arranged in a haphazard sequence by a rather contorted jet stream. And if these bulges are big enough, they can just sit there, with little to move them on.
Ironically for us, it’s a ridge of warm southerly winds up across Greenland which will help maintain our cold northerly winds downstream across the UK as December arrives.
MONDAY 27TH NOVEMBER – SUNDAY 3RD DECEMBER
If you build the ridge, you open the fridge
One more Atlantic low pressure system will take its milder, cloudier, damper weather away to the east of us during Monday. Temperatures, having briefly recovered to double figures in some places will start to fall again as the westerly wind gradually veers to a northwesterly. The blustery showers that follow will initially fall as rain. But as that northwesterly veers further to become a true northerly, so proper arctic air will begin to arrive.
… this weather pattern looks ‘stuck’
So from Tuesday onwards, I’m expecting those showers to turn to sleet or snow at times. As usual, it’s areas most exposed to those northerly winds that will bear the brunt of the showers. Certainly, some significant snowfall is expected across some hills of northern Britain in particular. But some more populated low-lying areas just inland from the sea could well be affected by the heavier wintry showers. Inland southern areas, with more shelter, can expect to see plenty of sunshine, but frosts will be widespread.
No two days are the same , but for the rest of the week, this weather pattern looks ‘stuck’. The ridge to the west will continue to keep the fridge door open for us. A wintry start to the new season is in store.
Another brief incursion of Atlantic air will raise temperatures through the weekend, bringing some damp weather in from the northwest.
MONDAY 4TH DECEMBER – SUNDAY 10TH DECEMBER
The north wind will blow and we will have…
The milder respite doesn’t look like lasting long. By midweek the next wave of arctic air will arrive as the cold pattern re-establishes itself. There will doubtless be increasing interest in the arrival of cold weather and the prospect of snow as we approach Christmas. It’s worth pointing out, however, that in the short term at least, the cold is not expected to be particularly severe. The seas around our shores are still relatively warm at this time of year and will have a modifying effect on temperature. Additionally the feed of winds is not from an intensely cold source.
Whilst the signal is for chilly northerly winds to continue to dominate, bringing frosts and further wintry showers at times, there are no clear indications yet of widespread disruptive snowfall. In fact, for many, welcome crisp sunshine will be in abundance
Some models do indicate winds beginning to come to us from east of north (which would lower temperatures further). Others indicate a more westerly Atlantic source again, which would usher in slightly milder, damper air.
Currently it’s in the balance.
MONDAY 11TH DECEMBER – SUNDAY 24TH DECEMBER
An advent of change as the big day approaches?
I mentioned in my last blog that if strong westerly winds in the stratosphere start to drill down through the atmosphere, our jet stream may also become more energised. This would help to iron out and sweep away the meanders that led to our cold block of weather .
There will be attempts from the west to bring milder, wetter weather
At the moment, however, if anything there are hints that the stratospheric winds may themselves begin to weaken. They may become rather more contorted through early December. If this signal continues, then we may be in for the long haul. With time, a persistence of the ongoing blocked pattern could allow the arrival of much colder easterlies.
Computer models will struggle to deal with any such linkage with the stratosphere. But on the balance of evidence, I’m expecting changes to be slow. So that means a predominantly chilly run-up to Christmas. There will be attempts from the west to bring milder, wetter weather, but they look half-hearted at present.
So, if you’re praying for a White Christmas, I’d say you’ve got a slightly better chance than most years. But then, that’s not saying much, is it? You’ve only got to look at the history books.