Model output discussion 24/01/21

[Daniel*]

Well good to see today we in London finally joined in, first real snow in 3 years !!! even settled in central. Not much but I was happy  

 

Models looking a bit all over the place helpful as ever, that milder weather has really been cut short.

[Battleground Snow]

Odd looking chart from the para at 306

 

Both GFS versions keep trying to throw up blocky charts, but they keep getting pushed back into FI, hope to see these pop up in the earlier timeframes in the next few days.

 

Edited January 24, 2021 by Battleground Snow

[Don]

3 minutes ago, Daniel* said:

Models looking a bit all over the place helpful as ever, that milder weather has really been cut short.

Nothing particularly cold showing up in the next couple of weeks with that EPS daily.

[nick sussex]

1 minute ago, Purga said:

It's a wonder you've got any hair left Nick

My frustration is really for UK coldies . I’m much more laidback when it comes to my weather down here . It’s only a short trip in the car up to the mountains , sods law this winter the skiing conditions have been great since before Christmas but sadly because of the virus the resorts aren’t allowed to run any lifts ! 

[Vikos]

A look in the stratosphere, there are still big question marks regarding the coupling between the vortex in the stratosphere (SPV) and the Troposphere (TPV). Repeatedly expected heat flows from the Asian Sector still do not allow a thorough regeneration of the vortex. At the beginning of the medium term range, in 10 hPa around the Laptev and Kara seas however, the medium term should shift rapidly towards Greenland, while an extensive anti-cyclone across the North Pacific sector did this forced "displacement" of the SPW.

Similar, there is also the downtransition area SPV to TPV wich can be made out, although the vortex currents there is quite weak. It is interesting that at least the GEFS indicates a coupling at the beginning of the medium term. So far so good. However, numerics models have massive problems with the pressure forecast throughout the arctic area. This is evident in the distinctive run-to-run Discrepancies in the pressure minima of sometimes several hundred kilometers, as well repeated strongly changing cross-polar cold flows from the Asian sector initially in the Canadian, now increasingly in the Scandinavian / Siberian area (possibly consequences of the indicated coupling between SPV and TPV?). A look at the ensemble spread also shows Uncertainties quickly become so lasting that any detailed work becomes obsolete.

But what is noticeable in the troposphere is an increase in the wave number comparatively short amplitudes and thus increased progressivity. This wave train is forced by repeated positive ones anomaly maxima in the 500 hPa geopotential field around the Aleutian Islands. These wander swiftly over North America to the east, but on a southerly track. This is owed due an abnormally high geopotential over the Canadian Arctic Archipelago or, in other words, a retrograde to the west offset negative NAO anomaly, which is even increasingly starting to the west, that the calculated NAO gradually slips towards the 0-line.

The NAO / AO however, remain in the negative range, with the member scatter at the end of the Increases dramatically in the medium term, but this is due to the shift of the TPV in the direction of Greenland, this caues a development wich is close to North Pole for then falling geopotential. This southern Rossby wave train now interacts over the medium term with an air mass over the eastern tropical and subtropical Atlantic, which is extremely warm with a view to the model climate (e.g. caused due to largely positive anomalies of the water surface temperature, but also by remnants of an intense subtropical that predominated until recently Anticyclones over the Canaries, the strong desert air advehed to the west and further heated by subsidence). This air mass is between the vigorous Atlantic lows and an anticyclone over Morocco, and it is (slowly weakening) led to the northeast.

Although the air mass cools down a little when it is lifted, nevertheless, the medium term can exceed 850 hPa in south-west and south of Europe Temperature values of 10-15 degrees are expected. The EFI underlines that unusual warmth in southwestern Europe with values of 0.8-1 and an SOT of partly over +1. If you look at the corresponding CDFs, you can see very steep ones Gradients (signs of high security) in the record range. Also the EFI 2m values (weekly averaged) this medium-term is about between the Iberian Peninsula and North Africa between 0.8 and 1 and on the basis of selected meteograms we are beyond the 99th percentile. Or in other words: Record values are particularly possible in Spain and across North Africa.

The western edge of this warm air mass gets in track of the rain Atlantic Low pressure Activity that initiates a pronounced so-called "atmospheric flow", which leads with predicted integrated water vapor values of 30-40 mm much moisture in to Western and partly also to Central Europe. That means that from the west swiveling low pressure areas following an abnormally warm and humid Have air mass and thus abundant precipitation for parts of Western and Central Europe becomes an issue.

[Uncertainty]

Deep cold v v close on the para 

Anyone else seeing a purple cat looking towards the U.K. there? Could be a sign...

Also, something notable, the usually mild ramping BBC monthly outlook goes all out for Greenland heights later in Feb, out of the range for the up to day 10 models for the moment, but not something I’ve read from them before really and they usually play cold chances down (probably because in recent winters we haven’t really had any!)

The extended EPS are, thankfully, very blocked again towards the end and, as the signal for a phase 6/7 push seems to have maintained we are still in the game for Feb. It must be stressed though that unless we get really lucky with that Scandi wedge( nearly in the para and definelty on the GEM) which is unlikely then we’re waiting really towards day 12 or 13 again for the next phase. Saying that the trend towards disruption this week is not the norm so if that were to happen for the day 8 system then we could be in for a nationwide battleground U.K. snow event. I’d give that one 20%.

Oh, talking about Greenland highs...

There it is, right on cue!

 

Edited January 24, 2021 by Uncertainy

[Froze were the Days]

1 hour ago, Mike Poole said:

You know, I kind of look at this and think, no this isn’t going to happen...GFS T174:

Where is the system in the Atlantic getting its drivers from?  Numerical modelling errors compounding is my take...this one is for the bin...

Got a big enough bin for all the runs your putting in Mike?

[weathermadbarnsleylad]

Can I order perb 16 from the 18z ens for breakfast please. Joking aside the ens were not great expect on perb 10 and 16 which were close to the - 16 850hpa. Hoping for better in the morning. 

[feb1991blizzard]

3 hours ago, weathermadbarnsleylad said:

Can I order perb 16 from the 18z ens for breakfast please. Joking aside the ens were not great expect on perb 10 and 16 which were close to the - 16 850hpa. Hoping for better in the morning. 

you wait till you see the the 0z suite - snorter coming up here!

 

[feb1991blizzard]

About 8 GEFS drop between -10c and -15c at some point between 4th and 7th feb and the run nowhere near finished yet.

[Godber 1]

3 minutes ago, feb1991blizzard said:

About 8 GEFS drop between -10c and -15c at some point between 4th and 7th feb and the run nowhere near finished yet.

Not the only model that's showing an easterly this morning.

[KTtom]

Total dogs dinner this morning at just 120, ecm now the only one which shows the deep low to the south for the weekend, if its wrong and ukmo and gfs is correct then last nights countryfile forecast is bust already! Mind you the rest of the run is a cold lovers nightmare!

 

Edited January 25, 2021 by KTtom

[sheikhy]

Is it me or is thst cold air across england even more harder to displace across central and eastern uk with more trough disruption from ecm and arpege!!this between 48 and 96 hours

[Jemma Croton]

Hello guys,

Wondering if you might help? Not about a specific output but I believe still quantifies as model discussion. 
 

I don’t post here all that much but am autistic with winter weather as an SI. Like many of you, I’m on the models multiple times a day this time of year and putting hours into poring over days etc.

I’n very lucky that I seem to usually back the right horse so to speak. I’ve had a good run for a number of years at calling which events will be snow and which will be a wash out etc. I’m used to being fairly accurate.

I can’t even now cats this year with the radar and get it right. Almost every event, it just isn’t going at all as expected. It will randomly dissipate about 5 miles away and turn to nothing etc. I’ve never seen this happen before. It seems EVERYONE is finding this hard to get right at the moment.

Anyway, it’s getting to me now and I feel like my one good thing has disappeared etc. Can anyone just simply explain why this set up is so challenging for everyone to forecast accurately etc?

I look up to you guys so genuinely, hearing a reason as to why will hopefully halt how totally demotivated I am from none of what I expect (even as a nowcast) actually coming to transpire. 
 

It may sound silly but I get so much confidence from knowing I’m good at the few things I have an SI in and between the virus, home schooling and my darling children finding this all very hard right now etc... this failing of mine is hitting me so hard and I’m kinda crumbling. This genuinely will help me a lot so I appreciate replies. 
 

Sorry if this is wrong place. I never want to post in the wrong forum etc but this fits as model discussion to my brain... just on a larger, generalised scale etc. 

Thanks guys and, as always, thank you for all your posts because this place and you lot (plus time and experience) is how I learned this stuff.

Edited January 25, 2021 by Jemma Croton
Mistypes

[bluearmy]

looking at the output I felt we were in a strange place where nothing made much sense beyond 4 or 5 days and then the ec day 10 evolved and I still thought this didn’t feel right so I compared it to yesterday’s 12z  eps mean for the same time.   I doubt you’ll find many arguments that the fi part of that ec op looks pretty solid ...

the gefs think it’s missing a wedge around Iceland just ahead of this timescale so the forecast still remains tough 
     

Edited January 25, 2021 by bluearmy

[Griff]

Gem still teases this morning 

[Tim Bland]

38 minutes ago, sheikhy said:

Is it me or is thst cold air across england even more harder to displace across central and eastern uk with more trough disruption from ecm and arpege!!this between 48 and 96 hours

Yes, ECM has moved a bit toward the Arpege but it’s not as widespread with the snow. Probably only temporary low ground midlands north and then high ground 

[Tim Bland]

Just for fun..some eye candy courtesy of the GEM at day 9 

[IDO]

It looks like the phasing and the spoiler lows have scuppered any chances of injecting sufficient wedge(s) to the north pre-d7, as most of us know, notorious at that range for something to go wrong!

D7 mean and gefs look in reasonable agreement:

d7> d10>

Between d7-d10 indications of a possible Atlantic episode allowing heights/wedge. The transient Pacific wave at d7 reinforces the Arctic wedge so by d10 an Arctic mean high.

Post d10 looks a mess on the gefs for a reasonable take, so best to leave it to resolve. 

Looking up to d8 on the gefs for London and rather typical average late Jan fare:

Still a handful of gefs going colder at that pivotal point around d6, but the trend is the other way and op and control on this run swerve it, though probably progressive with the Atlantic pushing the cold uppers east around d7?

[Drifter]

15 minutes ago, Tim Bland said:

Just for fun..some eye candy courtesy of the GEM at day 9 

Not just because it shows what I want it to show, but with the cold air in place, GEM actually deals with that Atlantic low and disrupts it in a more realistic fashion than the bowling ball barrelling in as per the other models. 

[Tim Bland]

15 minutes ago, Drifter said:

Not just because it shows what I want it to show, but with the cold air in place, GEM actually deals with that Atlantic low and disrupts it in a more realistic fashion than the bowling ball barrelling in as per the other models. 

Good point.  This week is an example of how the models struggle to accurately calculate how difficult it is to clear a cold block of air. There is almost always more resistance than the models show. 

[bluearmy]

possible take on the day 10 eps spread

1 says the upper trough has our name on it 

2 says the Azores ridge is out of play

3 shows where the trough digs further south 

4 are potential wedges or even upper ridges (more likely scandi one an upper ridge) 

[Anthony Burden]

GEM showing the continental block winning the battle at 216 hrs the rest of the bunch showing 

the Atlantic taking over.Interesting certainly can not rule out GEM,keen eye on ensembles.

[nick sussex]

Not a great start to the day with the ECM trend from last night strengthening , the  low speeds across the Atlantic on steroids , any wedge waves the white flag and scarpers off at day 6 .

After that it’s a case of the troughing sat over the UK as per the ECM op or more trough disruption and the return of the odd wedge to take the jet further south .

Whats very unlikely is any deep cold from the east or a Scandi high within ten days . 

Some snow is a possibility but we certainly need the ECM op to start disrupting more energy se wards for that to happen.

 

[The Beast From The East]

1 hour ago, feb1991blizzard said:

you wait till you see the the 0z suite - snorter coming up here!

 

Good or bad? ?