The Annual Mumsnet Christmas Weather Thread.

[OhYouBadBadKitten]

Its that time of year again, when amateur meteorologists, weather enthusiasts, the generally interested and those that hate the concept of weather forecasting all gather to guess, ahem, forecast the weather for the Christmas week.

Now given that at the moment we don't know what the weather will be like in two weeks time, this is clearly rather a tall order at present! But we can give it a go.

At the moment looking at the GEFS 35 day ensembles, which is the only weather model I can view out to that time period, it looks chilly, but not snowy, nor wet, just generally settled conditions.

Hello there @OhYouBadBadKitten and thank you for the thread of weather and ❄️ winter

You're welcome! I'll update the Christmas forecast at lunchtime. I've updated the winter forecast www.mumsnet.com/talk/weather/4626193-winter-weather-outlook

The GEFS control run has gone a bit nuts (technical term) for the Christmas period. This is definitely a just for fun commentary below.

Take a look at Birmingham. Follow the blue line.
www.theweatheroutlook.com/twoforecasts/gefs-35-day.aspx?loc=Birmingham

The 850hPa is at a height of around 1500m - it tells you the temperature of the air mass, irrespective of the time of day or any close to the ground heating influences. A very rough rule of thumb is that it needs to be below about -5c for snow.

The 2m temperature obviously should be below 0c, though of course snow can fall above freezing temperatures.

So what you can see is the pressure falling, temperature going below 0C and a spike of precipitation all on Christmas Day.

The control run is the ensemble model run that doesn't have any peturbations (little changes introduced). It clearly stands out on its own, well below the mean of the ensembles. But what a run!

In general though, away from this silly run it looks chilly/cold, but there clearly is a risk of some milder air being introduced and a return to more average temperatures for the time of year.

I don't think we should dignify GEFS 35 day with a response to the midnight output. Given how much the 16 day output has changed today compared to last night, I'll wait until tomorrow to update, rather than putting us on to an unnecessarily bumpy rollercoaster. (spoiler: it was pants!)

It’s getting colder☃

If it doesn't hurry up and do winter properly my nasturtians will be triffids!

Well we have much colder temperatures this week in rural Northumberland. It's 0.5 atm and the last few nights we've had a hard frost and had to scrape the ice off the cars! Very foggy here too. The gritters have been out and I've had the log burners on from early morning 🥶 ❄️

Good morning!
Im afraid GEFS 35 doesn't show a very festive Christmas period for the midnight run. Too warm for snow. However, neither does it look especially warm with the mean temperatures being average to below average for the period. Perhaps a little damp in places too.

This of course will probably change many times as we approach Christmas, remember this is not a forecast yet!

In the meantime, we do have our winter outlook thread to keep people entertained until then. www.mumsnet.com/talk/weather/4626193-winter-weather-outlook

Feeling much colder today in Syorks at last they're wilting!

The GEFS 35 day outlook actually shows the chance of a snowy Christmas day away from the south. Maybe it's time to place those bets on a white Christmas.

Given we don't actually know what the weather will be next weekend, I wouldn't place much money on it though!

I have some corvids (crows and magpies) that live near my house and every year I make friends with them via the medium of bashed up peanuts. I can see them increasing the food caches they are making in neighbouring rooftops, so I would say they're expecting a cold spell.

Science ^^

I would love corvid friends!

In what seems to be a very typical pattern as we get closer to Christmas, the outlook suddenly gets much milder just before Christmas. Todays GEFS runs show mild and damp weather for the Christmas period.

GFS goes out to the 20th now, so we are starting to get close to being for bringing it into the forecasts.

Netweather's Christmas forecast and (more importantly!), their Santa Shaker is back for another year!

That's probably one of the most positive starts to the Santa shaker that I've seen!

I've never seen the Santa Shaker before. I shall be shaking him regularly from now until Christmas Eve

It is quite positive - they're giving us a 25% chance of snow for us here in the Midlands!
They have their monthly forecast here which is interesting to read.

I thought it would be good to share how the GEFS model shows potential evolution of temperatures up to 21st December.

This is for London. I've chosen that location as being one of the less prone to sub zero temperatures.

As Gloria says, right out to end of run, the majority of runs keep things cold to chilly, but you can see that some ensemble members warm things up considerably. You would expect that sort of spread of results anyway, but it does show that cold isn't necessarily entirely locked in for the foreseeable.

(my personal definition of chilly is around 5-8c! It's obviously not an official term)

wrong thread! argh! not to worry, will repost!

Controversially I disagree with what the computer says onwww.theweatheroutlook.com/forecast/christmas-weather-forecast

I think it looks far too warm for snow Christmas on the latest GEFS run. I don't know if it is using data that I can't yet see, but take www.theweatheroutlook.com/twoforecasts/gefs-35-day.aspx?loc=Nottingham for example. The 850hPa temperatures shoot up after the 21st and stay there, as does the 2m temperature. So I'm a little confused.

Apologies for the lack of updates on this thread. It's partly driven by not knowing what is going to happen next week (see winter thread update!), never mind the following week. It's also driven by some confusion and my disagreement with the TWO computer. I still think that at present, in general it looks just too mild for snow during the Christmas period, looking at the GEFS 35 day ensembles.

However, the GFS model now reaches 23rd December, so I'll be able to give some deterministic forecasts soon (see winter thread for definition)

Too mild for snow.

It is ever thus

We are down to -3 overnight where I am.

Minus 4 here today.

Well, here we are, GFS is now just about in range for Christmas eve first thing. Remember this is a single deterministic model run, so it is one possible scenario, that may or may not be accurate.

After a warm up from around the 16th-18th ish, it show the potential for some pretty chilly air to move in from the west around Christmas eve or thereabouts. Upper air temperatures look mild in the south, a little cooler in the north. (not cold enough for snow) with surface temperatures nevertheless not far above 0c.

GEFS 35 day ensembles show a similar picture, with temperatures around the 30 year mean and around 5c or so on average. Tomorrow I should be able to look at how those ensembles are clustered.

I like cold, crisp days so let's hope this means some of those for me!