Focussed Model Discussion

[Paul_1978]

I can’t believe this thread is so quiet when we have some lovely looking potential north easterlies next week!

[BlazeStorm]

1 hour ago, Paul_1978 said:

I can’t believe this thread is so quiet when we have some lovely looking potential north easterlies next week!

True... Nobody dares to call it?

[Yorkshirepudding]

I realise this may be slightly off topic so I apologise if so and please feel free to move it to the relevant if needed... I posted this question in the mods and banter thread which could of been missed by the relevant people that could possibly answer it... this was the question. 

Given In certain areas Japan see’s the most snow fall on average than anywhere else in the world during winter, been an island like the uk and seeing something similar all winter like the lake type effect snow we do with a “Beast From The East” when winds come from a Russian direction, In the event of a SSW when the winds tend to reverse does/can this result in Japan getting a milder less snowy winter than normal??

 

 

[knocker]

Apropos nothing at all really but a glance, en passant, at the upper winds adjacent to the UK Essentially light and variable until you reach the top floor

And for good measure

 

Edited January 23, 2019 by knocker

[knocker]

The NH profile and surface analysis for midnight

A cold and frosty start in many areas with wintry showers over western Scotland and a complication in the south east from the waving front which has brought some snow down to low levels, and this may continue for a while. This also applies to the western Scotland, vis the showers,  and the odd shower may also occur down western and eastern coastal regions whilst elsewhere a sunny and cold day.

The showers will continue overnight which will generally be cold and clear with a widespread frost in the morning. But a frontal system is tracking north east around the high pressure to the west and the associated warm front is pushing east into Ireland with some patchy rain, and snow on the high ground.

The front only makes slow progress so much of the country will stay sunny and cold on Thursday but the rain, sleet and snow will make some progress and in particular effect N. Ireland and western Scotland.

Over Thursday night and through Friday the low continues to track north east and deepen and by midday is west of southern Norway, Thus the patchy rain moves east with the warm front and briefly much milder air is over the country  But the associated cold front is moving south east and by evening is bringing more persistent rain the the north with snow on the higher ground in Scotland.

The front and band of rain will continue to track south through Saturday with much colder air in it's wake with some frequent wintry showers, particularly over Scotland where again they will be of snow on the higher ground. The wind strengthening as it veers northerly

And this is the order of the day for Sunday. A cold, fresh, northerly wind with frequent wintry showers of rain, hail and snow

Edited January 23, 2019 by knocker

[knocker]

Moving briefly on with the gfs. The low to our east moves quite quickly away and after a brief ridge another front tracks south east down the country on Tuesday, associated with another trough that has tracked into Iceland from north east America. This brings some rain, sleet and snow with but as it clears the main trough fills and tracks south east as the high pressure to the west once more amplifies. Thus a very cold north westerly with frequent wintry showers is quickly initiated

Edited January 23, 2019 by knocker

[knocker]

At T132 the ecm has a trough in the Denmark Straits and an associated waving front tracking south east and bringing rain, sleet and snow to Norther Ireland and Scotland, along with a strengthening wind. The front quickly clears the south east leaving the UK in a showery north westerly but a wave depression that has formed on the front and has merged with the main trough north of Scotland as the high pressure amplifies in mid Atlantic by 1800 Tuesday.

Over the next 48 hours it drifts down into the North Sea and eventually becomes a non feature as it is absorbed into the next trough which tracks further east west of Ireland

Edited January 23, 2019 by knocker

[knocker]

Anyway while this going on the Arctic plunge over North America is some thing else

Edited January 23, 2019 by knocker

[IDO]

As you were this morning.

Variations on the general theme.

The potential in the next 10 days for snow and deeper cold in a cold seasonal flow, but a risk of the pattern is slightly unfavourable to some parts of the country at points but no done deal.

Models agreeing on a less cold Friday/Saturday but solid cold mean uppers from then on both GEFS and ECM, around 4-5 c below climate.

The ECM op, another run, another unlikely to be repeated for detail in the UK region past D8.

The GFS op throws up a UK ridge at D9-D12, yesterday they tried the same a few days earlier, so that may be overdone again, and neither GEM or ECM as progressive with the Russian High that far west.

A day or so to get the early February pattern confirmed, but I would guess, maybe a continuation of the systems/chunks leaving the Canadian PV lobe on an NW to SE trip feeding the euro trough? No strong signal that any Atlantic Ridge will be able to sustain a rise to Greenland. Any Pacific wave activity is muted due to the Asian trough disruption and the D16 GEFS mean suggests a +PNO rather than a ridge.

Usual caveats and all subject to change of course.

[BleakMidwinter]

9 hours ago, Paul_1978 said:

I can’t believe this thread is so quiet when we have some lovely looking potential north easterlies next week!

I rarely post anyway, but at present I am reading every single post really thoroughly because, for whatever reasons, nearly all of you are posting brilliant "teaching posts" - you post a chart and then say "you can see the feature I've circled in red; this is going to behave like this unless the feature circled in blue moves to the west in which case both will do that", or you post a fax chart and explain what the big curving line here shows or why there is such closeness between lines there, or whatever. Or you give your opinion and explain why you hold that opinion. 

For weeks I've only read the most recent couple of pages because there's been 15 pages overnight - but now I'm able to read the lot because it's manageable quantities and they are WORTH the reading! 

Thankyou, all of you knowledgeable ones!

[knocker]

Although varying in some detail the GEFS and EPS ext anomalies are very much in the same ball park. Upstream a high cell over Siberia and the vortex northern Canada with a strong upper flow exiting the eastern seaboard around the amplifying (to varying degrees) subtropical high towards the European trough. Diverging in mid Atlantic to some extent as the east European ridge gains a foothold into eastern Greenland.This looks very much like a continuation of the pattern the det runs are portraying of systems running around the  high pressure and dipping south east across the UK. Thus the influx of cold Pm air with unsettled wintry conditions and temps below average the percentage play

 

Edited January 23, 2019 by knocker

[Yarmy]

2 minutes ago, knocker said:

Although varying in some detail the GEFS and EPS ext anomalies are very much in the same ball park. Upstream a high cell over Siberia and the vortex northern Canada with a strong upper flow exiting the eastern seaboard around the amplifying (to varying degrees) subtropical high towards the European trough. Diverging in mid Atlantic to some extent as the east European ridge gains a foothold into eastern Greenland.This looks very much like a continuation of the pattern the det runs are portraying of systems running around the  high pressure and dipping south east across the UK. Thus the influx of cold Pm air with unsettled wintry conditions and temps below average the percentage play

 

Pacific anomaly aside, the agreement there is remarkable at such range.

[Sky Full]

For some reason I like to compare the outlook and performance of the weather models over a set period to see how closely they agree or disagree, so here are the four main models at +144 hrs (6 days out) which is pretty much the limit of the so-called reliable period:

                                         500s.                                                        850s

UKMO      

ECM         

GFS          

GEM       .  

At first glance they are similar but there are enough subtle variations between them at +144 hours to ensure there will be substantial differences at, say, +240 hours.  However, at this range we can be fairly confident that the overall conditions will be defined by a north-westerly flow originating from a cold location near Iceland and this will result in average or below average temperatures especially for northern UK.  As the low pressure system in the North Atlantic moves west the winds will progressively come from a northerly source which will prolong and perhaps accentuate the colder conditions at the end of the month.  It must be said that even within 144 hours there is scope for quite significant changes in the actual evolution but I will looking at the charts again in six days to see which model was closest to predicting the correct outcome....

 

Edited January 23, 2019 by Sky Full

[Singularity]

Troughs sliding in with only narrow, strung-out warm sectors running into a polar/Arctic mix of continental air to the east and stalling out, allowing the polar maritime air to also push on them from the northwest... that's a very complicated situation that I expect the models will have a very hard time resolving.

It makes me very suspicious of any output that keeps those troughs well-structured... ECM still the most glaring example of this despite some improvement from yesterday's efforts.

All this applies regardless of how much broader-scale HLB manages to establish prior to next weekend. It's then onward that the HLB becomes the more significant factor IMO as the tropical cycle becomes more supportive but to a degree that's not yet clear enough to make judgement calls with.

[Man With Beard]

Continuing a look at developments on the ECM clusters for the start of February:

Two clusters for 1st Feb; cluster 1 with a strong trough to our SE, and cluster 2 (the "op" cluster) has the trough more UK based. 

While I note that the op run cluster has grown from 10 to 23 since this time yesterday, I still think cluster 1 is a good one to follow as it reflects the very common extra step of progression as D4/D5 approach. That's just an opinion though. Cluster 1 would likely result in a good window for cold for some days.

OK, moving forward 3 days:

and I don't think we are any further forward from yesterday. We're about 50/50 between a block to the NW at 1st Feb being strong enough to allow a cold / easterly pattern to set in afterwards - or - the ridge collapsing to return us to a PM situation once more (with maybe a short UK high in transit as per cluster 4). 

That sounds similar to the soap-opera on the models of last week. However, my sense is that there is more ensemble support this time round for the easterly option. But not enough to tell the neighbours

 

Edited January 23, 2019 by Man With Beard

[knocker]

The EPS mean AO forecast sharply negative in line with the thinking that the colder aspect of the downwelling will occur at the beginning of February

[phil nw.]

The ECM mean charts days 5/10

would underline what Knocker has said with a tanking AO.

Quite noticeable how those purples are fading across the polar region in the next 10 days.I am watching to see if some weak heights develop to our north soon and the trend to cut through our mean trough,maybe 2nd week  or soon after.

Edited January 23, 2019 by phil nw.

[knocker]

A continuation of the wintry showers in the north west this evening, and even the wintry precipitation in the far south east, and as the temps starts to plummet  icy conditions will become widespread. But the complication could be through tracking south down the country which could bring some snow to lower levels

[knocker]

Nottingham just on the edge

[Paul]

18 minutes ago, kold weather said:

Hi mate, the Azores high looks t4he same to me, remember to ignore the surface features and concentrate where the lower/higher thicknesses are. That will give you of a clue of where things are. In this case both models have the Azores high ridging about the same amount. Where is the highest thickness both runs...yep, just east of the Azores.

Maybe a visual will help show the of the drivers, and why the runs are actually synoptically VERY similar.

1: Is the PV lobe that is heading SE. This force the jet onto a flatter trajectory which in turn flattens out any ridging. We saw the consequences of that in the GFS run. It is IMO by far the biggest part of this puzzle. ECM is nearly the same as well on its 00z run.

2: Is interesting, that is a weak high pressure cell, probably given the space to breathe due to No.3 being differently modelled. But the GFS is evolving it in the same way, just a little less robustly. BUT that sort of high is not the sort of high to stop the PV lobe (no.1) from coming south-eastwards

3: Is the main LP that is meant to come SE towards out shores. This is the feature isn't quite as well formed on the UKMO so the uppers aren't quite as cold.

I hope that helps explain why I think they are similar? It is just my opinon and I suppose you could again call it over-analyse, but there ya go!

Surface pressure do not make a pattern, but the 500mbs reflection usually will as that reflects the upper levels better (aka the lower part of the jet would be close to here).

 

[Deep Snow please]

Just copying this over here, deserves to actually be read. Great summary.

 

54 minutes ago, Kirkcaldy Weather said:

This thread is bizarre at times, so winter is over is it?

if we take the 1st Feb as a date 

2018   quite similar to the current pattern / possible repeated pattern moving forward with the  ridge in the Atlantic and the low bringing in a northerly, was winter over then? no that was  3+ weeks before the beast from the east began to show its hand

1st February 2016   the winter of 2015 / 16, now that is a better example of a "zonal" chart with a harder / unlikely route to cold - Winter 2015/16 was third-warmest for the UK in a series from 1910, behind the winters of 1989 and 2007. For England and Wales, it was the warmest winter in the series. December 2015 (UK anomaly + 4.1 °C) was easily the warmest December for both the UK and the Central England Temperature (CET) series from 1659. Remarkably, December had the highest positive anomaly for any month in the CET series by a margin of well over 1 °C. In comparison temperatures in January (UK anomaly +0.9 °C) and February (+ 0.2 °C) were mostly unremarkable. https://www.metoffice.gov.uk/climate/uk/summaries/2016/winter are we in that kind of position this year? chart from the 12z GFS which is causing unnecessary panic  even if that chart ends up being realistic  I would say it is still better than the 2016 chart with better heights toward Russia and trying to build into the Arctic and also the PV slowly draining away from Canada / Greenland whereas the PV lobe was stronger toward Greenland back in 2016.

1st February 2015  perhaps some similarities with northerlies etc but a pretty strong PV compared to where we could end up this year - At the start of the month, the UK was under the influence of a cold northerly weather type - Snow and ice caused some limited disruption during the cold spell of weather from 1st to 6th  - After a spell of settled weather, from 20th onwards there were some impacts from ice and snow across northern areas,  https://www.metoffice.gov.uk/climate/uk/summaries/2015/february

1st February 2014  again another example of "zonal" conditions - February was another stormy, very unsettled and wet month.- However, conditions were mild with any snow confined to the Scottish mountains. It was a mild month with the UK mean temperature 5.2 °C, which is 1.5 °C above the 1981-2010 long-term average, and the number of air frosts among the lowest in the last 50 years. The UK overall received 191% of average rainfall, making it the 3rd wettest February in the historical series. https://www.metoffice.gov.uk/climate/uk/summaries/2014/february I think we would be very unlucky to end up with anything as zonal / mild as that this year.

I think that is enough to highlight my point that we have been in much less favourable positions at this point of winter in the past and given the SSW and the downwelling only now beginning to have its say on conditions and the MJO possibly heading back toward a more favourable position I think writing winter off now is nothing short of crazy given how quickly things could yet develop for a colder outlook to take hold. 

 

 

Edited January 23, 2019 by Deep Snow please

[Deep Snow please]

8 minutes ago, kold weather said:

Just to give a quick illustration of the two broad camps:

Here is the GFS OP and Ensemble no.7 one fails at the northerly, the other comes off.

So here are both at 108hrs, I've circled the area to watch:

Both PV lobes are in a more or less similar location and strength.

Differences start to show at 132hrs:

The P7 run keeps it as one discrete lobe and moves its around the stronger vortex lobe to its NW, in a fujiwara method (spinning around a central point). GFS Op on the otherhand is literally slicing away the energy and it is escaping into the Atlantic, just like I highlighted on the UKMO 12z as well.

And VERY different 156hrs charts.

The Op has a flatter pattern and the NW flattening to a westerly, the P6 has a much more amplified pattern and a northerly.

So in future, if you want to have a good clue as to what way the runs are going to go, LOOK at the lobe over Canada an d its movement. IF it looks like P7 its game on, if not then there is trouble. EVERY single run that looked like the OP on the ensembles went on the flatten the flow and introduced milder air to the south. Every run that looked broadly like P7, was either cold, or very cold.

We should have good clue about the ECM between the 960-120hrs charts, and almost certainly know by 144hrs.

And this (sorry i meant to add this to post above).

Edited January 23, 2019 by Deep Snow please

[knocker]

A quiet consistency with the ext anomalies at the moment but with the Atlantic hugh pressure a tad more amplified the last evenings. Portending quite cold

[IDO]

A lot of the experts viz background signals are suggesting from late Jan the MJO will help with a Pacific wave. The mean above is, in fact, contrary, with a Pacific Trough. The GEFS have been picking this up for a day or so and bringing it forward and more defined. We wait to see if other models change their MJO signal.

This after D9 would likely mean that the Atlantic high is further east, mixing with the euro trough, and aiding wedges to our N/NE. With the PV to our NW probably struggling to send lows SE anymore it could be a stagnant blocked euro pattern with embedded cold. Whether that can develop into something from the east would be a good question in 7-10 days time, assuming the status quo, though downwelling remains elusive on the models.

GEM also blows that low up, around D7, along with the GFS op and control, but this is too far out to worry about such a new development, likely the models overdoing it and will trend to less vorticity going forward. Though clearly, it would be detrimental to the pattern of cold for a few days, so no thanks!

The mean for London: 

If the op and a few members have picked up the wrong signal viz the deep low then the recent trend remains the call for the Atlantic sector.

In the reliable, cold apart from Friday-Saturday, less so, but the pattern reluctant to trend towards deep cold ATM.

We wait for further advice.

 

[knocker]

The ecm's take on the wave that develops to the west and deepens as it swings east over the UK at the weekend. Strong winds heavy rain.and snow on the high ground over Scotland and cold on Sunday in the fresh  northerly with some squally wintry showers