Mucka

Tuesday night marked record low temperatures in various places. Copenhagen experienced its coldest November night in a hundred years, with the Frederiksberg district recording -7.7 degrees, the lowest since 1919. Over the past 150 years since records began in 1873, there have been only 13 instances of temperatures hitting -15 degrees Celsius in November, with the most recent occurrence being in 1993.

My gut feeling is that we will see some "interesting" output tomorrow evening, but it is just a hunch based on how much the models are currently struggling. There are (relatively for only 72h) large differences even at 72h with how milder mobile air reacts to the cold block as it pushes up against it which is often a sign something is afoot one way or another. Note the difference in orientation of the low and how far NE it is in comparison on GFS ECM V GFS 12z 72h And that difference is compounded throughout the run and made very obvious by just 96h ECM V GFS 12z 96h As a rule of thumb the Euros tend to model this part of the Atlantic sector better and GFS tends to be too progressive. It is still unlikely any of the models have pattern nailed down when there is such divergence at 72/96h Tomorrow morning will probably be more of the same but the evening runs maybe more enlightening, at least for general direction of travel, if not ultimate destination, for mid month cold prospects. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4969366

My gut feeling is that we will see some "interesting" output tomorrow evening, but it is just a hunch based on how much the models are currently struggling. There are (relatively for only 72h) large differences even at 72h with how milder mobile air reacts to the cold block as it pushes up against it which is often a sign something is afoot one way or another. Note the difference in orientation of the low and how far NE it is in comparison on GFS ECM V GFS 12z 72h And that difference is compounded throughout the run and made very obvious by just 96h ECM V GFS 12z 96h As a rule of thumb the Euros tend to model this part of the Atlantic sector better and GFS tends to be too progressive. It is still unlikely any of the models have pattern nailed down when there is such divergence at 72/96h Tomorrow morning will probably be more of the same but the evening runs maybe more enlightening, at least for general direction of travel, if not ultimate destination, for mid month cold prospects.

Copenhagen Recorded the Coldest November of the Century ETURBONEWS.COM Denmark experienced its coldest November night in 30 years with a temperature of -15 degrees Celsius. Copenhagen also br...

Which way is the output heading? Run to run variability and comparing model runs against each other can muddy the waters. Here is a like for like comparison of ECM, UKMO, GFS 12 runs today V yesterday for Dec 8th with 850 temps to more clearly differentiate the boundary between milder and colder air masses and how far East that milder air pushes. Today V Yesterday 12z runs 144h comparison charts. ECM UKMO GFS I think the trend is pretty clear so let's hope it continues into tomorrow as still a way to go, rather than reverting back more Atlantic dominated.

GFS being GFS, easily the most progressive with the breakdown. But if we want some comfort then we have to look at how much GFS has backtracked already from yesterdays 12z output in pushing the Atlantic through (And it is still the most progressive model!) UKMO is much less progressive again this afternoon. 144 comparison So yes, clearly the Atlantic looks like getting in, bar dramatic changes of how the Atlantic lows are modelled, but we can still hope for blocking to reassert by mid month for now. As said this morning, it is all about how much undercut we can get post 96/120 and the further W we keep those lows before any disruption then the better chance we will have.

I think you got up glass half empty this morning matey. Both UKMO and GFS have basically added caveats to any breakdown. They aren't going to flip to cold overnight, it is all about bigger picture at the moment and getting things moving the right way which they have this morning. This is what GFS 00z was showing for Dec 8th just 2 days ago compared to this morning on the right. And UKMO for Dec 7th It may be the Atlantic still wins out and we get a flatter pattern into mid month, but the output, at least for now, is suggesting the Atlantic may well get in for a time but the cold air to our NE is not going anywhere in a hurry.

GFS 00z certainly making yesterdays 12z look very progressive. GfS 00z V yesterdays 12z 144h UKMO also derailing the Atlantic train to some extent compared to previous runs. So it still looks like the milder air will get across the UK but hitting the buffers when it comes up against the cold block to the E/NE Still time for changes but currently it looks like it will be decided on whether we can get enough undercut post 120h. If we can get further improvements on this mornings runs this evening, including ensembles, then things will get interesting again.

The longwave pattern does suggest a breakdown and I already stated that in a previous post, but here we are discussing how far E and how quickly the Atlantic pushes and the fact is the GFS Op is extremely progressive in pushing milder air NE. It is unusual for the Op to be so out of kilter with its ensemble suite in such a short a timeframe 96/120h and it is very much at the progressive end of the scale even if we disregard the signal mean being distorted with the more blocked runs that you are dismissing. How far NE the Atlantic pushes from any breakdown matters if we are considering the possibility of blocking returning before mid Dec

That GFS Op went against the ensemble mean by 96h as does the control in being too progressive. By 120h the difference against the mean is a bit of a red flag. GFS Op V GFS mean 120h

This GFS run, whatever it shows in the end, seems unlikely with how it handles the low from just 48h, serenely making its way E/NE with absolutely no influence from the dense cold air to its E/NE. Not sure how much that will affect the overall longwave outcome but a strange run anyway. LOL goodbye Ireland I think the milder air now looks very likely to win out for a time, it is just a case of whether we can quickly re-establish some blocking toward mid Dec or whether we revert to zonal. That looks to be very much in the balance even if we can't keep the current cold and blocking. GEM with a decent effort.

Tues night/Wed morning. Turns to rain unfortunately.

You would probably take the human forecast as the model output will fluctuate, not to say human forecasts don't fluctuate sometimes. It could also be they are talking about later Monday when rain for the S is forecast and have dismissed that spell of snow Sat night/Sunday morning for central England and N Wales.

MetO calling a rain event again which conflicts with their own model "Turning cloudier and warmer from the southwest with rain spreading north later on Sunday and into the new week."

"Coming soon..." SNOW MACHINA: DISRUPTION PART DEUX

It is going to be interesting to see what actually develops post 120 hours as there is obviously some scope for change there as cold air attempts move W and mild Atlantic air E with battleground somewhere around the UK. The models are now generally favouring the Atlantic push bringing Westerlies and milder air around Dec 5th/6th but if the lows disrupt SE then some snow is possible with a possibility of maintaining the cold from any ensuing ridge. A breakdown is favourite but still time for some relatively short term developments in favour of cold days 4 to 6

Imagine this sort of developing blocking pattern backed around 1,000 or so miles W and we would be locked in the cold. Wishful thinking or direction of travel?

Anyone considering GFS output should be very weary of current Op runs. This is how far W it has adjusted the low at just 96h from yesterdays 12z and it is still much further E than the Euros Look to Euros for guidance out from 120h for now would be my advice.

Chicken and Egg. The jet won't be modelled to buckle if there is no blocking modelled. Here is 180 GFS V Icon jet and pressure charts

The main difference between UKMO and GFS is that GFS is more progressive with the breakdown of the ridge allowing the Atlantic low to phase push E/NE which is the precursor to the break down and why I don't trust it with the longwave pattern post 144 at the moment. GFS V UKMO UKMO thus has the low much further S by 168 and shows the other possible snow chance around Dec 3rd/4th I mentioned as a possibility yesterday, Currently the models are toying with the possibility of building a ridge close to or over the UK and up toward Iceland thereafter and Icon shows that while the UKMO would go onto but flatter and further E. The GFS obviously isn't showing that this morning but then it may well be wrong earlier or of course it may onto something with a quicker breakdown. There isn't much sign to any sign of them wanting to properly amplify the Atlantic and re-strengthen blocking to our NW, maybe just a slight hint from GEM but that is more because the original ridge hangs on longer. For now though I'm going to stick with the idea of more amplification upstream post 144 than currently modelled and a less progressive pattern but otherwise the GFS type breakdown rather than a Scandi high. Anyhow, let's see if any low lying areas of England can see some snow over the coming week. UKMO has the low just clipping the SE Midlands and Wales benefit from the 2nd low

I wouldn't take either ECM or GFS FI output to heart. I think GFS is wrong with the breakdown but with building heights over Scandi and ECM wrong with building blocking over Scandi as they both have the pattern too far E and too flat, especially GFS. Most likely scenario for me is for blocking to recur as an Atlantic ridge to our W with NE flow heading into week 2 of Dec but if that is overrun instead for the mild to win out, at least for a time. At least ECM keeps it cold and blocked so I would take that if I'm wrong but we would have to hope we could get the blocking further N as the pattern evolved for further snow chances. PS Could be another chance of widespread snow on top of Thu/Fri's hope before then, say in around a weeks time.

Latest MetO update somewhat more reflective of the output. "Sunshine, with scattered showers for many. Some snow, mainly on northern hills. Overnight frosts with fog and icy patches. More persistent rain or snow possible in the south on Thursday." Not sure who was on morning duty but they may have been out Sat night.

Odd MetO forecast this morning given the charts. "Brighter skies develop on Tuesday and Wednesday before rain and showers into Thursday." No mention of snow even for high ground or the North, quite strange. It may well be a rain event or non event int he end but you would think they would cover themselves with snow in the charts by at least mentioning the possibility

Chilly with rain sleet or snow would sum it up for most for the next 10 days. Later in the first week of Dec might see better prospects of widespread snow as the Atlantic tries to break through but lows hopefully disrupt to our W rather than breakdown the blocking pattern completely. Somewhere might get lucky end of Nov, start of Dec anyway before looking too far ahead.

Yes, we can expect a bit of flipflopping yet and we both know neither GFS nor UKMO will be right at 144, they are just variations from an awful lot of possible outcomes at this stage. Can't help but be excited when they show our favoured outcomes though and lass than a week away now. How will it end?