Model discussion highlights

[Eagle Eye]

1 hour ago, minus10 said:

Hi Eagle Eye, can i ask you a question...the Global wind Oscillation chart looks similar to the MJO chart...its not though is it? Presumably phases 6-8 associated with colder weather?

Also, PNA?...AL (Aleutian low?)

AL ?

Still learning so i thought i'd ask the proff...

   

 

Lol, sorry it took me so long to reply, did half of it in lesson shhh.

PNA is the Pacific-North American area (well actually its the Pacific-North American Pattern but I'm lazy)

The GWO is a generalised chart

Phases 4-7 have increasing AAM

Phases 8-3 with decreasing AAM

5 through to 8 with colder patterns generally (support for mid to high latitude blocking via tropical forcing etc...)

Al - Aleutian Low

I also talk about the frictional torque balancing it out but what do I mean?

Well, as the mountain torque event happens, the upwards wave flux pushes outwards from the Tropics and the anomaly quickly becomes uniform between the latitudes and that leads to a frictional torque event that decreases the AAM. Generally its a pattern that repeats every couple weeks but can be shorter or longer (I.e a fairly persistent Ural Blovk with have cold on the other side of it so generally cold near the Himilayas quickly balancing out any +VE EAMT events as +VE events are warm air over the mountains and naturally the opposite is true for -VE events.) depending on the background signals. Both the SHAL (Siberian High - Aleutian Low) and the MJO affect the EAMT events though I'm not entirely sure how for each one.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4785860

[minus10]

27 minutes ago, mb018538 said:

This 8-14 day 500mb plot certainly looks a lot colder than milder...

...yes , one of the coldest i have seen  i think... 

...Interesting as looking at the mean anoms for ecm, gfes and gem 0z you can see a theme of heights stretching from the e/ne to nw over the pole around to ne Canada /usa and into the Atlantic..

...with the trough in the middle centred just to the east of UK..

...not too dissimilar to the 500mb plot..

Gem geop 500 illustrates the possible link of heights to the north fairly well..

....certainly more interesting than traditional sw zonal pattern...

...after day 10...well not going to worry about that yet...

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4785717

[Eagle Eye]

With the transition towards the phases 8-1-2 and the balancing out of the +VE EAMT event with the large frictional torque reaction this should see a return to the more Nina looking pattern. This transitions via the loss of AAM led by the -VE EAMT event (partly impact upon by the MJO) and that will likely retract the Pacific jet towards late January. We would therefore see the effects probably around early February but it'll have to be looked at through the starting atmospheric state at the time. Everything has to be in context but if we can get a SSW in before then, we may have to rely on it occurring before we lose the abnormal upper Trop heat transfer as for a major SSW, keeping up the upward heat flux is very important. Like I've been saying for a while. As long as we can keep up the Ural Block + Aleutian Low then the chance is pretty much always there (e.g. similar pattern analogs of 2017/18 and 2018/19) but it's important that we don't fall on the side of a Wave-1 SSW under the area of warming as displacement here does not equal amazing cold chances even given a SSW for us. I'd much prefer the first wave to push towards the PNA area in the Strat with the AL in place and then the UB to follow after that. Let's see how we go...

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4785795

[Eagle Eye]

14 minutes ago, minus10 said:

So positive EAMT events (warm air) have the effect of increasing AAM...whereas negative (cold air) events decrease AAM....hopefully i have understood that correctly. 

Absolutely spot on, warm air over mountains = gain of torque and vice versa and no problem, I'd already completed the work in lesson anyway .

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4785907

[Daniel*]

New development spawns a deep ish low in Bay of Biscay that should help hold back Atlantic high.

>

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4785933

[AdrianHull]

14 minutes ago, Vikos said:

can someone explain me those 1085 over Greenland?

It's called the Greenland Anticyclone and probably one of a few areas in the world where the saying "it's too cold to snow" is true. 

Because Greenland has such a cold surface temperature that extends to lower atmosphere making it super cold which basically blocks any warmer lower pressure from making any inroads to the centre of the country. Leaving the interior very dry and cold and causing the phenomenon of a constant high throughout the year.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4785995

[Nick F]

EC due an upgrade this year, increasing ens to 9km resolution (same as high res), extended ens members will be run daily and with 100 members! GFS got a lot of catching up to do. 

103rd AMS Annual Meeting

AMS.CONFEX.COM

---

In 2021 ECMWF successfully introduced two new operational cycles, 47r2 and 47r3...

The next science cycle, 48r1, will be implemented in 2023 on our new HPC system in Bologna. This will see an enhancement of the ENS horizontal resolution to the TCo1279 grid (approximately 9km), the same resolution currently used by the HRES. There will also be an increase of the data assimilation resolution, with a new soft-centred approach to the Ensemble of DA (EDA) used to calculate background error covariances for 4D-Var and to initialise the ENS forecast runs. Other important changes in 48r1 include running the extended range ensembles daily and with 100 members, a new multi-level snowpack model, and use a new object orientated approach to run the 4D-Var atmospheric data assimilation (OOPS).

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786000

[Singularity]

EC42 support for a SSW hasn’t totally gone but has reduced from about 20% of the pack to near 12%.

I expect it’s highly sensitive to just how long high pressure remains across Barents/Kara with some coverage of adjacent lands to drive cross-mountain flow hence vertical wave activity flux.

The faster it gets pushed east, the sooner that flux subsided and the less likely the warming is to be sufficient for fully displacing the polar vortex and triggering a SSW.

Theres also uncertainty regarding the Aleutian low, just how long that persists for. The longer it continues the better the odds of a very large wave-1 (displacement) or even a wave-2 (split type) event.

There’s a reason why SSWs aren’t reliably picked up on at over two weeks lead time.

The possible one for early Feb seems a coin-toss to me, we can only guess which way it will actually go.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786067

[Daniel*]

29 minutes ago, feb1991blizzard said:

EC46 looses SSW signal

Not sure it’s fair to say loses SSW signal, about 10% do a reversal. I think this was quite predictable to be honest based on what we’ve been seeing still mean goes 20 m/s that’s not a strong vortex, think at moment it is ~50 m/s. Also note signal not for strengthening following weakening as we sometimes see. Maybe Thursday will be more insightful.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786065

[knocker]

24 minutes ago, Vikos said:

can someone explain me those 1085 over Greenland?

This has already been answered but just to reiterate the key factors are the height and size of the ice sheet. For example surface pressure from the Geosummit sounding at midday was 656mb with a temp of -52C

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4785997

[Rain All Night]

The first three weeks of the latest EC46 and CFS height anomalies, both reasonably well aligned and showing some blocking, and neither finding a positive anomaly over Iberia in weeks 2 or 3:

The EPS clusters for week 3 give us some ideas on what might be causing that blocking signal - perhaps some ridging to our northwest although not necessarily very strong - perhaps the CFS is seeing something more like clusters 1 or 4 with its positive anomaly around Iceland?

I finally found a site that offers 7-day rather than 5-day anomalies for the GEFS and... it seems the chart for the first week is always broken ... we can see though that the GEFS doesn't share the semblance of agreement that is seen between the EPS and CFS in week 3 (although it also doesn't find Iberian heights).

But are these weekly charts any good? ECMWF helpfully provides a chart that shows you how well each week verified, which can be found here: https://charts.ecmwf.int/products/mofc_multi_verification_anomaly_family_flowz500?base_time=202212050000

The top left chart on the grid of nine small charts below shows the actual anomalies from the chosen week. The four charts on the grid that I have outlined in red are the forecast charts from when this week was week 1, 2, 3 and 4 (from the Monday EC46 runs). Next to this grid I have pasted the Northern Hemisphere profile from the middle of that week, for comparison (oh how we miss it!). You can see that the week I have chosen is the one where we were all cold, and that ended with the Northerly that made us even colder.

I have to say that the forecast when it was week 4 was pretty good, somehow better than when it was week 3!

And here are the CFS charts from when that week was week 1, 2, 3 and 4. Not quite as good as the EPS on this occasion, but you can see that it was sort of trying to tell us about the blocking to our north being significant, and that the polar vortex would be on Asian vacation.

Charts here (mess with the dates in the URLs to get charts from the past): https://www.cpc.ncep.noaa.gov/products/people/mchen/CFSv2FCST/weekly/

And finally, a couple of recent "weather regime frequency verification" charts, also from the ECMWF site: https://charts.ecmwf.int/products/extended-regime-probabilities?forecast_from=latest_13

The extra row of blocks at the bottom shows you which regime actually verified vs. the one that the ensembles had preferred.

The cold period lasting roughly 29 Nov - 16 Dec has been designated 'Blocking' for the first half of the spell and 'NAO-' for the second half of the spell. So you can see why these two regimes get people excited whenever they show up on the regimes chart.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786227

[carinthian]

23 hours ago, carinthian said:

Aye, its a good morning. First snow for weeks has arrived just in time. Snowing quite heavily with temp of -0.2c currently in the village . A bit wet but its a start. Broad agreement again  UKMO/ECM for next week with some advance of the polar trough through the British Isles. Of course , alignment of the Azores high crucially important going forward. A projected powerfull NWly jet to develop later next weekend in the vicinity of NW Europe will have an impact on positioning of the Atlantic high. Looks like UK and much of Western Europe will be on the colder side of the jet for atime and could be open to some quick sinking low formations  to develop  on its northern flank. The movement of the high does not look static and will ebb between lateral and retrogressive pole ward. So potentially some fast changing weather on the cards and snow likely to feature in the forecasts later in the week. However, will the squeeze on the polar trough be sustained going forward 168-240t ? Thats the million dollar question and only the behaviour of the Azores high has the answers ! Anyway, overall quite pleasing charts on offer this morning, especially welcome here in the snow starved Alps.

c

Good morning from a very snowy Eastern Alps. In yesterdays post I mentioned formation of new lows to develop on the Northern flank of the NWyl jet into the British Isles. The one showing for early next week ( UKMO chart below ) and backed by ECM/GEM is the one that could potentially produce some widespread snowfall. Its tracks SE across Northern Britain into the Southern North Sea as the week progresses with some very cold air associated with-in its development. I have a feeling this formation and track will create a bit of excitement next week. Good luck with this one.

C

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786298

[Nick F]

32 minutes ago, feb1991blizzard said:

surely the temperatures give the best representation of the temperatures though, that's why i have never bothered posting them charts or even understanding what values equate to cold 2m temps, although i guess people post them to show that the 850 and mid level profile aren't always a good guide to what we feel.

Theta-e not really the best guide to surface temps and determining if snow will fall to lower elevations, theta-e is good for determining the dryness and stability of an airmass.

I would use the partial thickness (850-1000mb) for the best guide to forecast potential for snow, below 129dm, ideally 128dm, and snow is possible. Dew point forecasts also useful, want 0C or below, always a challenge in Pm flows at lower elevations, due to long sea track over the Atlantic and mixing out of cold air by SSTs warmed by gulf stream. Surface temps can fluctuate due to sunshine or cloud cover, wind and intensity of precipitation, so temp forecats not always a good guide. 

Netweather 850-1000mb thickness for next Tuesday daytime shows below 129dm across southern Britain but a question of whether there can be ppn too. Obviously this will all change.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786351

[Ali1977]

5 minutes ago, goosey007 said:

Hi all great buzz in here tonight must be something brewing ….ps can anybody give me a brief overview of what a snow row is I get the higher the number the greater the chance but how does it correlate to the ensembles graph ? First year I think I have seen snow row mentioned unless I have been living in a cave

There are 30 ENS members, if the snow row says 17 then 17/30 are showing snow over whatever location is selected 

So in Birmingham fir instance, 18/30 are showing snow early next week - which is a pretty good signal at this stage 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786652

[bluearmy]

Struggling to put the fat on the bones past the first trough - it’s going to get colder but then it looks difficult to predict for how long, if we get any milder incursions ahead of a further trough dropping through and then if we just flatten out (prob still nw/se) or maybe even see some amplification to our north/northeast 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786695

[Blessed Weather]

In fairness to the GFS it 'spotted' next week's substantial troughing into Europe for around the 18th/19th back on the 7th January - which was then a full 11 to 12 days away. Here's what all 3 runs that day (0z, 6z and 12z) were showing. With a trip to the Alps coming up on the 20th January it certainly caught my attention and I posted the charts in the Mountain & Snowsports thread. Good news for the Alps to see ECM and GEM now supporting the same scenario.

7th Jan 0z  6z  12z

As a matter of interest, has anyone got the latest model verification stats please? I've lost my link.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786720

[Mike Poole]

ECM clusters interesting tonight.  Start with T120-T168 and here it is all about the depth of the cold plunge:

Prefer any of clusters 1-3, op is in 2, 4 doesn’t really cut the mustard.  

T192-T240:

This is the interesting, there are only 3 and widely different (why the mean looks underwhelming!).  Cluster 1 maintains the PM flow, cluster 2 has us in mild air but WAA into Scandi, cluster 3 westerly then block to NW heights into Greenland to an extent.  

T264+

Heights into scandi preferred, all but cluster 2, cluster 1 a bit too far east.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786674

[nick sussex]

Quite an unusual set up if it verifies of that shortwave dropping se on the eastern flank of the Atlantic high .

The general rule in these situations is the shallower the shortwave the better chance of some frontal snow .

The slider as it’s known is normally elongated running nw se and because of that the flow ahead of the precip is more s to se rather than sw .

Its really a case of not removing the surface cold as it heads se .

Thats why deeper features with the more rounded shape aren’t what you want to see .

There’s quite a lot of uncertainty with the likely to be infamous shortwave because the models will play around with varying solutions .

Mainly due to how much amplitude there is upstream , how much it engages the deeper vorticity over southern Greenland which in turn effects its depth.

So the chance is there for some frontal snow more especially for the north and Scotland .

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786394

[Nick F]

Not often you see a direct strong flow from southern Greenland, which looks very cold, could be rather raw next Tuesday ...

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786730

[Catacol]

1 hour ago, January Snowstorm said:

Two significant things were on board for the last cold spell

John Holmes weather charts - tick

Met Office suggesting cold - tick

Lo and behold the models follow suit this evening. Now all we need is a ramp from Catacol and we are back in business  

Haha - I'll wait a day or so. I have an inbuilt suspicion of mid Atlantic ridges that look like they are topplers. Way too many disappointments from this kind of wax/wane scenario to nail my wintry colours to this kind of setup yet. I'm always chasing the pot of gold scenario of sustained and deep cold but at moments like this I always remind myself of Feb 96 when I saw more snow in the South of England than I have ever seen including 2010 and 2018 - so the sharp trough sliding into Europe and pulling an easterly in behind it CAN bear fruit. But that kind of scenario has been rare indeed as a realistic option on the table since that 1996 setup.

With the Pacific Jet in overdrive currently following positive torque and a sustained medium high AAM profile supported by the lagged impacts of MJO 7 which that paper I mentioned the other day suggests will be strongest from around now until Jan 25 we should start to see some much better charts such as those today - but as yet it feels like a winter context just not quite prepared to allow NW Europe to tap into proper cold. EPS rolling out and this 96h chart has a lot going for it

but still we have a stubborn trough over us with a positive anomaly to our south, and the strong tendency towards ridging to our east and west is unable to open the gates to cold. 

A watch and wait scenario still for me while we see whether trop driven patterns like this can improve further or whether strat developments begin to further catch the eye.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786702

[Dangerous55019]

Hello everyone. 

So for the first time this year, I thought I'd have a quick look at the CFS v2 four weekly anomalies, to see if they can help any of the more experienced members on here shed some light as to what might happen. 

Week 1 - 10th to the 16th January: Low pressure pretty much centered over us here in the British isles, and the North Sea. Wind, rain, and Atlantic onslaught ... Pretty much normal for January.

Week 2 - 17th to the 23rd January: A little bit of a change happening here... High pressure out over the Atlantic, and stretching out over the North Pole. Low pressure is now centered over Scandinavia. To me this would leave us in a northerly airflow. Now there is a possibility that the high pressure over the pole could start feeding in cold air into the low pressure over Scandinavia, and a possibility of snow showers affecting the eastern side of Britain. It could also be picking up on a classic 36 hour northerly toppler... Only time will tell...

Week 3 - 24th to the 30th January: High pressure is now pretty much over the top of us, and also stretching out over the Atlantic! To me that says that we could well see the return of frost and fog... Your classic dull grey January days. 

Week 4 - 31st January - 6th February: All Change! The high pressure of the previous week is now moving off out, and over the north sea, low pressure now out in the Atlantic, just off the west coast of Ireland, could well leave us in a mild southerly airflow. To be fair, if this was a chart that appeared over the summer, I'd be personally get quite excited because of the threat of thunderstorms! Could we get thunderstorms off this kind of set up in February? Only time will tell. 

 

So there you make of that what you will! Hopefully this will help out some other members on here. 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786856

[Blessed Weather]

10 hours ago, Mike Poole said:

Here’s day 6, 0z and 12z:

GFS well into 4th place on 0z, 5th behind JMA on 12z!

Here’s the link:

GFS Verification: G2G All Models (ACC)

WWW.EMC.NCEP.NOAA.GOV

 

Thanks Mike. Digging around this morning and I found ECMWF's own verification stats versus other major models buried within their model output "app" and, of relevance to the UK's location, they produce stats for the North Atlantic and for Europe. They also offer stats at the 500 hPa level or for mean sea level.

Without being too scientific, a glance suggests the GFS is frequently 10+ percentage points behind ECM's verification for our part of the globe. Another point of interest is that the various models verification performances generally go up and down in unison, but there are some instances when a model will buck that trend. A good example is to look at the North Atlantic chart and the period 29th Dec to 1st January and wonder what synoptic set-up caused the performance of all models over that 2 days to significantly slump? It would be a great exercise to map the various model output charts with their subsequent verification to see what model handles what situation better. (But don't look at me, lol! ).

ECM verification charts for the 5 days to 5th Jan:

500 hPa N. Atl  Europe

Msl         N. Atl  Europe

Source: https://charts.ecmwf.int/

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786861

[carinthian]

Morning all. The latest UKMO run shows an upgrade in cold and snow potential for the British Isles as it starts to tap into some of that very cold lobe of air from the East Greenland Sea. Monday looks like the coldest day for some weeks across the UK with sub 528 dam (500-1000mb ) covering much of the country hence increased risk of snow showers. It will probably take a couple of more days before more defined details can be ascertained.  Going forward , most of the models , apart from GFS indicate negative NAO. This should in theory be conductive to weaker Lows, hence from Tuesday onwards the low being shown to form to the NW cannot yet be certain in timing or movement. ECM moves this development at some pace and hence a snowy Euro trough on the cards, UKMO latest just seems to be holding back on this for the time being and of course GFS  op showns something completely different with WAA across the British Isles and a build of pressure. Never easy is it, but our guys fairly confident in ECM out puts this morning, in fact one of the forecasting agencies out here have issued advanced warning for heavy snowfall for the next 2 weeks, especially for the Western and Northern Alps.

C

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786876

[mushymanrob]

13 hours ago, RainAllNight said:

The second chart begins on Wednesday 18th, which happens to be the end of the current MOGREPS, and continues into the following week. I'm now going to have to call on the wisdom of someone like @mushymanrob to understand what this chart might be telling us about where we could be going next - I do note that the official commentary mentions that confidence is below normal during this period due to a large-scale pattern change occurring 

The official 8-14 day 500-hPa height blend consists of: 10% of Today's 0z GFS Ensemble Mean centered on Day 11, 30% of Today's 6z GFS Ensemble Mean centered on Day 11, 30% of Today's 0z European Ensemble Mean centered on Day 11, and 30% of Today's 0z Canadian Ensemble Mean centered on Day 11

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below-Normal, 2 out of 5, due to a large pattern change that looks to be occurring during the forecast period with a wide range of solutions evident in the ensemble models.

https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html

Cheers.... as i see it, the 8-14 day chart is not good for those seeking cold. However the 8-14 day chart didnt really pick up on next weeks Northwesterly too well.
Flicking between the 2 charts, the green flow contours suggest slight ridging off the AZH becoming closer to the UK, suggesting to me that IF this evolution continues then high pressure will build to our South as the GFS 00z suggests in FI. The TPV is still there over Baffin, and between that and the AZH the mean flow is Westerly . the 546DAM line is over most of England and Wales, so whilst the mean flow over the UK is just North of West, the origins are Westerly .... That chart to me suggests mild and unsettled, and IF that slight ridge continues Eastward to arrive South of the UK, a Bartlett cannot be ruled out.

Whether this chart is accurate, or my interpretation is, only time will tell.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786877

[Cold Winter Night]

It looks like we can be fairly confident of the Atlantic Ridge building next week, with the trough plunging into Europe, bringing a N/NW flow to us around the North Sea.

The EPS regime chart moves the ensemble firmly into Negative BLO for days 5-7.

If this will result in snow on our own doorstep remains to be seen, that will have to be monitored in the small scale short term models, but at least there are decent snow chances for many next week, and seasonal temperatures.

The regime chart also shows a general return towards the central circle (no regime), and based on the clusters there is a tendency to move the Atlantic High East, over the UK, and, in the extended period, towards the Southern Scandinavia/Baltic region. Not the coldest kind of Scandi High, and the futher NW in the UK you would be in a worse position, although the opportunity for a better setup remains, which would make those milder Westerlies a temporary thing.
The alternative seems to be another NW-SE aligned lazy attempt at cold Pm flow (cluster 2).

Going through the individual members at the very end (360h), most actually have a quite meridional look with blocking near Europe. There is certainly potential (yes, I hate that word as much as you do…), and there are not many members that show a classic Pos. NAO.
Real cold is not found within the 15 day ensemble unfortunately:

But because of the hemispheric view on the ensemble members at Day 15, interest remains for the last part of January.

Meteociel - Panel ECMWF/CEP

WWW.METEOCIEL.FR

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786972