Mid-Winter: Forecast and Model Discussion commentary

[bluearmy]

 Mike Poole today’s runs have increased the chances of a cold easterly before the end of the month.   But from a low bar.  Let’s see what momentum is picked up over the next day or two (if any) 

[Battleground Snow]

 feb1991blizzard

Yep a more robust block compared to the 12z run, not as good as ecm,  but it will hopefully disrupt the Atlantic 

[northwestsnow]

Trough disruption..

V interesting .

And that wer that !

Edited January 12 by northwestsnow

[Don]

1 hour ago, Jason M said:

Would probably take the average temperature down by a couple of degrees but we would still be on the windward side of a large ocean. 

Just a couple of degrees could make all the difference though, particularly in marginal setups?

[feb1991blizzard]

 Battleground Snow  bluearmy

I wonder if this could be one of those gradual GFS switches from Atlantic to more amplified solutions over a few runs, and gets an E'ly, a BexleyHeath special if you know what i mean!, i very much doubt it because its usually, or used to be years ago, moving towards an ECM solution but it don't tend to work like that anymore, in fact i would be far more confident in my forecasts if the models were the same as they were about 12 years ago and there hadn't had any upgrades.

[Don]

1 hour ago, WYorksWeather said:

I would want to see at least a decent portion of the extended range options go properly cold before I change my view on this - a full-on northerly or north-easterly would need to be a serious possibility.

I would also like to see the Metoffice express this scenario as a possibility in their monthly forecast, too.

Just now, feb1991blizzard said:

BexleyHeath special if you know what i mean!

Mr M?!

[Battleground Snow]

 feb1991blizzard

I think at the 10-11 day lead time there is a lot of water to pass under the bridge, but you can definitely still say that the gfs is still progressive with deep Atlantic troughs 

[feb1991blizzard]

 Don Yes - a sneaky movement towards an Easterly from the GFS after modelling not handling energy distribution at range - his bugbear.

Edited January 12 by feb1991blizzard

[Mark Bayley]

 bluearmy we'll no doubt get a pub run special before the week is out!

Before that dry and milder, especially further north and west. Models have  double digits into Scotland. Wonder if we'll see issues of flooding as the week progresses?

[Don]

 Mark Bayley Mild has actually been downgraded my area for both max's and minimums next week.

[Penguin16]

 TSNWK 20 years from now. “I’m so sick of that Greenland high. Can’t even go outside for half of year without wearing enough layers of clothing to resemble a circus tent. Everytime blowtorch SW are modeled it gets watered down and that Greenland high appears out of nowhere again and now this time it’s a Greenland low abc. I just wasted 2 weeks staring at the models, staying up half the night, walking about like a zombie and sleep deprived to the point of illness and all we ended up getting was 10 minutes of drizzle and 8c, hate this place”

[Battleground Snow]

@feb1991blizzard

GFS Control is a much closer match to the ECM run!

[Nick B]

 northwestsnow Hi, while I agree winters in the UK and Western Europe could become a lot colder on average in that scenario, I think Canadian winters (without wishing to create a strawman argument, many might interpret the suggestion  here as the type of cold experienced in the heart of Canada on similar latitudes to the UK) aren't something we'll see here for two reasons:

1. Due to the direction the earth spins, general prevailing winds will continue to originate from sources to the west of here. Even though large areas of the Atlantic may be cooler, there's still more than enough heat energy there to still mitigate our climate here.

2. A significantly large continental land mass such as Canada at this latitude will additionally always develop deep cold pools much more readily in wintertime.

Nevertheless, I do agree there would be scope for Atlantic-sourced winds to be significantly chillier than they currently are. I think the far more worrying modelling of that scenario is what happens with areas of significantly decreased or increased rainfall, and how that could affect vital crop yields through the growing season. The effects of such changes in local annual rainfall could well be utterly catastrophic.

 

In the modelling, there's a very gradual  increase in the disruption of systems meeting the European blocking high, but I'm not yet seeing enough in the models to suggest it will make enough inroads to get any meaningful low pressure into Southern Europe to support a Scandinavian high... yet! That for me is the key. Can the disruption establish or enable low pressure in S. Europe to take hold. Also, the longer it takes to do that without a decent enough cold pool in Central Europe, the longer you'll need to wait for sufficiently frigid 850s.

Edited January 13 by Nick B
Including something on topic!

[Snowysniffles]

 blizzard81 Maybe I’m hallucinating, but are we seeing the harbingers of an AMOC collapse in the near future with charts like that one? Maybe it’s just too much wine tonight but drawing a circle around the whole Northern Hemisphere, it looks like the cold area is notably larger (assuming things from the pressure patterns), and that the Polar Night Jet is significantly south shifted. 

I mean we often see dramatic charts in the extended, but not sweeping resets of the circulation outside of an SSW or season change on operational runs in the extended quite consistently. I mean we had ECMWF a couple of days ago digging the POLAR night jet close to the equator. The fact that’s even showing as possible on numerical model output, and often similar to the AI models, should be ringing more alarm bells than it seems to be. Radical shifts like this should not be swept under the carpet merely because it might help or frustrate the next “chase”. We need to look at the shifting baseline of what it is we are able to chase.

The most moderate 10+ day operational model run I could find from the evening was GEM 12z and even that is wacky. 3 days and you go from that to a Greenland High, and it’s partly self-generating (but not just over Greenland, an important distinction due to topography). That level of pressure raise in that time without a yellow blob heading up there on this chart is not something within our understanding of what goes on there. There’s a pulse of heights from the Pacific side but it’s comparatively unremarkable and is brief. GEM being the least dramatic and still it’s mind-boggling in several respects - I’d invite you to dive into the European view and watch pressure areas behave unusually and unpredictably. The physical assumptions we make about pressure areas over various land, ice and seas are being upended, rapidly imo. I’d love to see what a major SSW that splits the SPV would do to all of this. Uncharted waters...

[feb1991blizzard]

Can anyone feel another slidergate coming on end of month? Not really my cup of tea i admit though.

[JamesL]

 northwestsnow https://oceanographicmagazine.com/news/amoc-atlantic-tipping-point-keeping-climate-stable-greatly-underestimated/#:~:text=More than 40 of the,for countries around the world.

[Jordan S]

Not really feeling like finding the charts to post as I'm not feeling too great atm and just wanted to give a fairly quick worded summary only.

The broad theme since my post yesterday remains largely similar, but differences such as..

1. A somewhat slower paveway to unsettled conditions with a stronger emphasis on southerly winds for a time initially, even though noted to some degree yesterday with again the emphasis on western areas seeing any risk of wet conditions initially, in fact its likely be largely or completely dry on the 17th/18/19th for much of the UK bar perhaps the west with slightly wetter weather here, particularly for Ireland/northern Ireland by the 18/19th with some spells of rain here possible, any more widespread unsettled changes slowly developing and spreading erratically east during 20th/21st, initially milder.

2. More widespread wet and windy conditions quite likely for most or all by the 22nd or 23rd of January onwards as lows make more successful inroads, instead of past the 18th/19th, potential still of very strong winds at times along with heavy rain, occasionally cold enough possibly of sleet/snow showers in the north behind departing lows (in particular any deep ones), but to a lower extent/risk on the northern flank of any deep lows crossing the UK, most likely in the north/northwest and largely on high ground, most frequent wind direction most likely being westsouthwest/southwest 22/23rd- 27th.

Overall slow moving patterns initially, but more progressive by the 23rd.

Overall this is similar to previous post for upto 27th,  most likely outlook may change further ofcourse, though I wouldn't anticipate by much at all with only timings changing slightly perhaps, will try and update soon.

Something favourable more widely snow wise and to lower levels possibly develops by the end of January 27th+/early February, that may be the period to watch, still most likely unsettled but as the Jetstream perhaps digs further south into Europe.) it could raise snow risks for all. Have a lovely week of I don't post and take care.

[Legend.Ice]

Morning , I have written it hundreds of times, let me write it again, if there is no high pressure at the top, strong cold weather will not come down, there is still no increase in GPH in the Arctic region, we will continue with weak colds, maybe after Last week of Jan , there is hope…

[TillyS]

Good morning all.

Interesting times. The coldest start to January for 15 years with the CET currently sat on 1.5C and some stunning snow-scenes from up north, especially Scotland. If you haven’t looked yet into their regional thread then it’s a visual feast for lovers of UK snow. A cold start indeed.

Despite being repeatedly told by the BBC / Meteo Group that "the high pressure is moving away with mild air sweeping across the whole country," the high pressure in fact isn’t budging very far and it isn’t mild in the south-east. Nor is it going to be particularly mild all week. Temps in the south-east are likely to struggle and won’t be much above the old cold average, if at all. Scotland, in the true south-westerly flow, is a different story.

After this week is when things start to look interesting. There’s still no real clear sense of a resurgent Atlantic and there are some tentative signs of a return of cold set ups with a Scandinavian High appearing in the GEM and particularly last night’s 12z ECM. Add to that the growing number of cold to very cold ensemble members in the GFS and the final third of this month looks on a knife-edge at the moment.

First those 18z and 0z ensembles:

Then the 18z ECM:

True, the 0z is a typical ECM flip-flop:

(No wonder the ECM scores highly in NH correlations when it’s able to offer up so many different possibilities from run to run  )

Personally I’d say it’s 60:40 that we are going to see a cold, perhaps very cold, final week of January. Armed with that thought, was it so very wrong of me to look up the winter of 1946-7? Perhaps. But as a reminder, there were two cold snaps before the real action began as late as 23rd January … OK so everything says the climate is now very different and that was a one-off but it’s still a reminder that Spring lies far to the south and there’s a long way to go of this winter.

[Gowon]

Nice chart from the JMA, it's trying to build a scandi at the end :

[mulzy]

Just for fun - day 14 ECM

 

[IDO]

 

 GFS>  EC>

The three main models at D10. A heavy chunk of the tPV dropped into the Atlantic. That will be difficult for any heights to our east to repel. There is no sign of cold from the NW, as the 850s will warm out by the time they reach most of the UK. So, we will have to wait for the last week in January to see if the western trough can warm out and allow the cold in the east to push west. But the means and even the D16 GFS do not currently support that:

GFS op>

The best hope is that we will see further changes in the data to help us have a colder outlook. Certainly, the Atlantic Ridge option remains off the table, so cold from the east seems like a tentative hope.

D16 GEM mean:

FWIW GFS op looks progressive according to the London ensemble pressure graph:

Edited January 13 by IDO

[Jacob]

9 hours ago, Mike Poole said:

 The UK will still be downstream of the Atlantic Ocean, it might just be a bit colder

A few studies suggest a cooling so severe that sea ice reaches England. These effects will be offset by GW but not this much

[AO-]

Good Morning all, 

May I present you another cherry? The GEFS still leaves room for letting the cold back in somewhere in the last 10 days of January. Member 11 this morning is just stunning. I have seen worse ensembles and the battle between the Atlantic and the Euro high is yet to come. Perhaps we can see some improvement the next days or just downgrades because the Atlantic wil win. Interesting times for sure. 

Edited January 13 by AO-

[That ECM]

2 hours ago, feb1991blizzard said:

Can anyone feel another slidergate coming on end of month? Not really my cup of tea i admit though.

 

Would love one but can we have it from the east this time please?

It’s the unfancied big outsider but it’s the one I would want. The truth is that something from the north west (not great for most) is by far the more likely TBH.