Model output discussion - Closing in on Christmas

[joggs]

22 minutes ago, TSNWK said:

Felt it was looking a tad better between 144 and 174 with that low climbing further west up against Greenland.. however it really seems to have become progressive afterwards and this 186 is flatter that the previous by day 9 we are much flatter upstream, high topples and vortex forming to our next west. Appears that gfs wishes to remind of us last night.....

Yes, going on its progressive way as per.

I only take note of it upto 92hrs or so.

[Tim Bland]

00z Vs 06z in Fi . Lots to be resolved! 

[swfc]

I'd suggest anything going forward is probably going to come from the nnw. Atlantic ridging ete looks the form horse with the jet going sse. Possibly into early January but has folk have said very fluid output 

[Battleground Snow]

A wide range of outcomes in the ensembles out to 180... GFS struggling to resolve movement of that low out of the states.. 

I wouldn't rule anything out untill we get ECM and ukmo down to 144 for the  Xmas period.

P16 is good again.

Edited December 17, 2020 by Battleground Snow
Typo

[feb1991blizzard]

Another one of @CreweCold's How would you like your PV sliced coming up.

[Daniel*]

The beginning of a significant warming continues to get closer not far in FI now. Impressed by how persistent GFS has been.

I think we should expect a quite weak vortex into early January which should ease fears if disconnect fades we’re doomed, it will take a boost over next week but this is looking temporary....

[Bricriu]

1 hour ago, feb1991blizzard said:

For those who say a vortex chunk has never hit the UK with bitter cold before, i refer them to this chart.

All snow convective event even for Liverpool, not even close to being rain.

Yes. Indeed. It was a fantastic time. I doubt I'll see anything like it in my life time again

[Johnp]

The atmosphere certainly seems to prediposed to ridging and blocking at the moment, but the cards just aren't falling for us right now. 

I think it's just a matter of time until we hit the jackpot personally.  I'd love a January freeze up, when there's a prospect of any snow hanging around for several days, as opposed to the new fangled cold spells we tend to get in March nowadays!

 

[northwestsnow]

Until we have continuity upto 144 I guess FI really is FI...

[carinthian]

Crazy chart to end latest GFS run if you believe it. Don't think I have seen so many individual low pressure cells on a chart like below. Think I counted 8 or 9 !

C

[Ice Day]

Looking at the 850's scatter at just 120-144 on the 6z GEFS highlights the uncertainty in the short-term.  Can't say I study them in depth, but I would have thought that differences of more than 10c between the highest and lowest at that range is unusual?!

[Radiating Dendrite]

Just now, Ice Day said:

Looking at the 850's scatter at just 120-144 on the 6z GEFS highlights the uncertainty in the short-term.  Can't say I study them in depth, but I would have thought that differences of more than 10c between the highest and lowest at that range is unusual?!

I would not say so in the winter.

More unusual in summer given the narrower 850 range that we tend to see.

[West is Best]

27 minutes ago, swfc said:

I'd suggest anything going forward is probably going to come from the nnw. Atlantic ridging ete looks the form horse with the jet going sse. Possibly into early January but has folk have said very fluid output 

I think this post nails it.

I'd only add that there's the ever present risk of a return to flat zonality but, if not, then this is likeliest scenario and one we've seen all too often in recent years. Not bad for Scottish ski resorts when the gales abate enough for the lifts to open. Any sustainable block looks very unlikely to me and there is a notable absence of cold pooling in places which once upon a time we could bank as certainties: over Russia into Siberia and Scandinavia, even Eastern Europe. It's just not there at the moment.

I feel like we are Canute before the incoming tide. There's no escaping the fact that climate change has altered our winters.

Don't shoot me. It's not my fault.

[Radiating Dendrite]

Just now, West is Best said:

I think this post nails it.

I'd only add that there's the ever present risk of a return to flat zonality but, if not, then this is likeliest scenario and one we've seen all too often in recent years. Not bad for Scottish ski resorts when the gales abate enough for the lifts to open. Any sustainable block looks very unlikely to me and there is a notable absence of cold pooling in places which once upon a time we could bank as certainties: over Russia into Siberia and Scandinavia, even Eastern Europe. It's just not there at the moment.

I feel like we are Canute before the incoming tide. There's no escaping the fact that climate change has altered our winters.

Don't shoot me. It's not my fault.

The lack of cold pooling is just a symptom of the synoptics we have seen over the recent month though. There are certainly some very cold areas in the Northern Hemisphere, areas of Siberia are touching -40c 850s.

This can also quickly change as well, more especially now we are into 'proper' winter.

[Kentish Snowman in Yorks]

8 minutes ago, Ice Day said:

Looking at the 850's scatter at just 120-144 on the 6z GEFS highlights the uncertainty in the short-term.  Can't say I study them in depth, but I would have thought that differences of more than 10c between the highest and lowest at that range is unusual?!

Interesting chart that.

The spread at 850 level seems far greater than the spread at 500 level.

Also with regard to the 850s the spread seems greater at days 4-6 than it does at days 7-8?!

Interesting model watching that is for sure and far better to keep tabs on that than looking at long fetch South Westerlies! 

Edited December 17, 2020 by Kentish Snowman

[johnholmes]

The question to ask is

Which of the model runs out to 240h looks, regarding say the 552 DM line the most like the 500 ,b anomaly charts I showed earlier. They have a much higher probability of showing pretty closely what the 500 mb flow will be 6-10 days from now and probably a few days beyond that?

 

[northwestsnow]

The scatter on GEFS suggests lots of uncertainty with how this low behaves to our west as we head through the early part of next week.

Which of course has a knock on effect for Christmas and beyond...

Lots of interesting charts so I suspect this thread might be busy for a wee while !!

[fromey]

I have just watch a very interesting video from a uk organisation ( who we can’t mention) and it was a in-depth view for next week, they highlighted the massive uncertainty on the low coming off the ESB, there models were all over place and the presenter kept highlighting the uncertainty, now if this organisation with all there computing power and data don’t know then how are we supposed to know, and yes I know some are just saying what the models are showing! But I think we have a very interesting week ahead, I wouldn’t  write anything off just yet!! God willing we will get a cold Xmas albeit snowless for many but I think the fun and games may and I say may begin after and in to the new year (hopefully)

[IDO]

Nothing in the gefs suggesting a roadmap for post d8. We remain in a fluid modelling period with even the first Atlantic ridge evolution still unresolved despite the consistency of the gfs op for it to fall? The only certainty is that the ridge will build!

d9 gefs: 

[ITSY]

Control also goes with the sliding PV 
 

Just a note of course that the winds are so strong coming off the NW coast that it's nowhere near cold enough to produce anything white away from the hills - Scottish resorts though would be pleased! 

[Kirkcaldy Weather]

10 minutes ago, West is Best said:

I think this post nails it.

I'd only add that there's the ever present risk of a return to flat zonality but, if not, then this is likeliest scenario and one we've seen all too often in recent years. Not bad for Scottish ski resorts when the gales abate enough for the lifts to open. Any sustainable block looks very unlikely to me and there is a notable absence of cold pooling in places which once upon a time we could bank as certainties: over Russia into Siberia and Scandinavia, even Eastern Europe. It's just not there at the moment.

I feel like we are Canute before the incoming tide. There's no escaping the fact that climate change has altered our winters.

Don't shoot me. It's not my fault.

Runs lately show the big blocking high to the east to increase in strength over the next few weeks, remember the gfs run I posted few nights ago had 1070 hpa but quite a few runs showing 1060 / 1065 hpa. Gfs +6hr temperature chart for this afternoon  plenty cold enough, associated with the section of PV and also the blocking high mentioned across Siberia / to the east 

 

[Man With Beard]

We're certainly still in the game for a cold Christmas Day, and not at the point where a white Christmas can be ruled out for any location. Taking both the GEFS ensembles (posted above by IDO) and this morning's ECM clusters, the likelihood for 25th of a ridge forcing a northern-based flow is growing, not decreasing:

While these patterns often result in cold and dry days, you can never rule out a trough getting caught up in the flow. Looking at other parameters, I'd expect any trough to produce snow.

So White Christmas remains low odds, but, at least there are still odds! Meanwhile a white christmas of the "frost" variety continues to look a strong contender.

 

 

[alexisj9]

56 minutes ago, northwestsnow said:

Until we have continuity upto 144 I guess FI really is FI...

Fi so where ever that low leaving the state's today is lol. 

[mushymanrob]

28 minutes ago, johnholmes said:

The question to ask is

Which of the model runs out to 240h looks, regarding say the 552 DM line the most like the 500 ,b anomaly charts I showed earlier. They have a much higher probability of showing pretty closely what the 500 mb flow will be 6-10 days from now and probably a few days beyond that?

 

Using this method would save a lot of excitement/disappointment caused by the wilder swings of the ops.

It was mentioned above by @swfc that our weather looks like coming from the NNW, and the anomaly charts for several days now suggest a mean upper flow from the Northwestern quadrant. So cool unsettled likely imho.

Speculating, all anomaly suites suggest positive heights to latitudes north of the UK.  If we can get cyclogenesis to stop developing over the Eastern seaboard and subsequent energy injected into the jet stream, then maybe a more substantial Greenland block can develop. Im not "coldie" but imho that chances of a proper cold spell this winter are much higher then usual, ive been feeling this now for several weeks as northern blocking has developed.

[Vikos]

1 hour ago, Daniel* said:

The beginning of a significant warming continues to get closer not far in FI now. Impressed by how persistent GFS has been.

I think we should expect a quite weak vortex into early January which should ease fears if disconnect fades we’re doomed, it will take a boost over next week but this is looking temporary....

That's one stronghold of GFS, if there is smthg on the horzion regarding a warming, GFS is quite accurate in predicting it very soon