Lots of hype and excitement right now on the forums and social platforms about the possibilities of a cold spell for the end of November 2018 and the future of Winter 2018-19. This has become apparent due to the charts that several model runs have produced since the weekend. Let’s discuss what the latest models show and take a realistic approach to the potential of this spell.
What do the models show?
To start off the discussion on the model output, let’s have a look at the shorter to medium range models before getting onto the long range models.
The GFS 12z run showed a Scandinavian High retrogressing to Greenland by mid to late next week forming into a massive blocking feature. This results in bitterly cold northerly to northeasterly winds plunging down the UK around Friday, 23 November onwards. There would be plenty of snowfall in the country especially in the north and northeast. Daytime temperatures around low single figures in the south but struggling around or below freezing in the north, would be very remarkable for November! The evolution of the pattern here is akin to what happened in late November 2010 which culminated then in the coldest December since 1890 of course. That’s not what is going to happen this time around, it’s an interesting comparison nevertheless.
This run of the GFS model is an extreme example of what can happen if the pattern sets up this way. However, I cannot stress enough that this is an extremely unlikely scenario to occur. This is only one run showing this extent of northern blocking over Greenland and a deep Euro trough. Would need charts like such to be in the more reliable time frame i.e. before 72 hours away, appear on more runs and more models before we can take it seriously! If it started appearing more than just this one run then we should start thinking about it and start issuing multiple weather advisories as it would likely result in a prolonged cold spell. For now, it’s just for fun. Do not have to take more from it than that at this stage.
The idea of the high retrogressing on the GFS 12z operational run is supported well by its ensembles at 10 days away.
The ECM 12z was far less extreme than the GFS model with high pressure not quite fully retrogressing to Greenland. However, there is still a block of high pressure just to the north and east of the UK in between Greenland and Scandinavia exerting some influence into the Arctic. The Polar Vortex is split with one part going to North America and another over to Siberia. With this, cold air and snow would build up over Siberia fast and if easterly winds were to become a thing by say December, we could be in for some very cold conditions indeed. No ‘Beast from the East’ type event mind you as it’s too early in the season for such to occur.
The ECM is rather cold and damp for the UK in the short-term but longer term, this would have possibilities of encouraging cold spells during Winter 2018-19.
The UK Met Office (UKMO) only goes out to next Monday currently but it shows a block of high pressure over top of Scandinavia eagerly awaiting to retrogress to Greenland it seems with an easterly wind in across the UK. It would be fairly cool and damp on that day in the UK and if the Scandinavian High were to retrogress, we would likely be bringing in a northerly or northeasterly wind. However, if the high didn’t retrogress, the country would likely continue a damp and cooler than average theme with not a lot going on. All of this is Fantasy Island so unreliable and we can only theorise.
The UKMO Glosea5 model updated this weekend for Winter 2018-19 and it showed a massive change in the pattern of the last few months and including from its October update.
The November update shows an area of above average heights building over Greenland with an area of below average heights over Central Europe and going into the UK. This leaves the mean wind direction as northeasterly or possibly even easterly. This would be a cold Winter pattern and was the pattern of some well known previous Winters such as 2010-11, 2009-10 or 1978-79. This pattern becomes even more extreme into the Jan-Feb-Mar 2019 period with a large blocking feature extending from Greenland to Scandinavia to Siberia, kind of akin to Winter 1946-47.
Big change indeed from its October update which showed the complete opposite of below average heights over Greenland and above average heights to the south drawing in a westerly flow. This only reveals the reliability of long range seasonal models and why you cannot take them as gospel. What I will say is that the last time the model produced such northern blocking in its November update was 2010.
The Glosea5 is not alone in showing such extensive northern blocking for Winter 2018-19 as the JMA and Beijing Climate Centre models do too.
A lot of models point towards some cold conditions in the future for the UK whether next week, the end of November or Winter 2018-19. Long range seasonal models really ramping up on the chances of a cold Winter setting up for the UK and much of Europe. What do we take from it all? Well, as it’s all in the unreliable time frame, we cannot take any of this serious right now. If we do, you’ll see future updates on the matters including our week ahead or weekend forecasts. For now, it looks as though high pressure will build over Scandinavia this week into next week gradually turning the winds into the east after an initial very mild interlude for November in the UK later this week. Europe is still fairly mild and it’s only November so it won’t be overly cold if we do turn the winds into the east. However, as the trough digs into Siberia, the land will just cool and cool continuously over time. If we keep seeing this pattern reoccur, we will find ourselves in quite a potent cold spell.
If the high retrogresses to Greenland, we could find ourselves in a significant cold spell sooner than if we get easterly winds. Precipitation likely to fall as rain for now as the air is looking just a bit too mild for next week. We’ll have more on the conditions of next week in our usual week ahead forecast this Sunday.
It’s a good time to monitor what could lie ahead but let’s stay realistic and not go overboard! We’ll keep watching and post another update when things get more reliable and concrete.