[Model output discussion - deep cold inbound?]

Hi res is showing precipitation to west of Ireland Tuesday turning to snow, 100 miles out to sea. Thats a good indication that anything trying to push in will be readily falling as snow, The Southwest approaches has precipitation the same.

Can i add, slightly off topic The latest BBC (stav  Danaos) only went as far as Sunday. I compared the graphics and they very much showed the UK Met output. Not ECM.  They will do paid services for forecasts when the weather is potentially disruptive ( i believe). 

[Model output discussion - deep cold inbound?]

7 minutes ago, Don said:

A good post pyrotech.  Do you think it's a case of the favourable MJO vs a strong jet stream courtesy of brutal cold coming out of the USA and seeing which gains the upper hand moving forward?

Yes i think thats what some of the model runs are showing, but  some runs have a less effect East North Atlantic ( UK) so its intriguing how those models are handling the contrast in air temperature, the resulting jet stream and the low.  I would hope a seasoned forecaster with vast experience like John Holmes would pop in and give his thoughts. (There are quite a few others on here too)  I need to look at 500mb charts to see what is driving the data correctly or incorrectly. 

There could be some interesting warnings pop up over the weekend  (for next week) if MET output remains same, but that changes like the other models by run to run, especially 5 day plus. Interesting as in where they are !

[Model output discussion - deep cold inbound?]

My post was about the models and what is shown in Fi

Its probably the most interesting part of model watching right now, as cold and snow is almost guaranteed for the South East during Saturday - Tuesday.

Its likely for some snow even imby. Many areas will see some snow and settled snow.

How much and where exactly is pointless as it will change and cause some disappointment and others will have nice surprise.

Its fun thou and we all enjoy seeing the possible accumulations mount up, including me.

However  the real interest now in meteorology is watching the models try to get a grip on the length of the cold spell and the depth of the cold. The battleground can be amazing.  So far, we have seen the cold air retreat and return South 3 times, its really stubborn against the cold dense air. I have never said the cold spell is over, i just posted two charts from 2 main player models with one possible scenario that their operation runs suggest, with then the Ensembles contradicting somewhat, what they show. The UKMO and previous runs have indicated a better solution.  What would be useful on here is some valid analysis on the heights to our North and the effect on Jet stream (including USA storm) and how the models are changing them. The MJO with lag is perfect for a more blocked pattern, for me it must be the contrast in temp  coming from USA that is causing the changes predicted, but are they likely or over cooked.

Please do not see this as in anyway taking away the snow many of us will see over the next 5 days plus, but if we can look for cold in fi when not in place, surely we can look in fi for signals from the models on what is likely next.  

 

[Model output discussion - deep cold inbound?]

The cold spell is on but the certainty evaporates around 9th/11th.

We have two major models now that deepen the low until it is strong enough to affect  the cold air, we also have heights over Greenland diminishing.

If we look at the ECM and GFS at 11th Jan, There are strong South Westerly winds that will rapidly change any frontal snow back to rain. 

However, the models are playing with a number of opportunities in that range.

A Strong jet stream is the main driver, it changes from a North West too South East jet, to becoming a Westerly Jet. This allowed by the forecast loss of heights to the North over Greenland. It is also affected by The high over Scandinavia slipping away but strengthening. Both of these can be more stubborn than predicted.

Question is how much these scenarios are credible due to that severe cold boundary coming off the East Coast USA.

 

The Ensembles show a lot of uncertainty on this scenario, i show Cardiff, but they follow similar path in Essex so this is a good example.

We have seen that low become less deep and a slider and that could return.

The breakdown or attempted breakdown may not be something many want to talk about, but for many in South UK and especially those in South West this is very often the route to any meaningful snow. So sorry if this talk about breakdown is not the main talk for those in North Sea Coastal zones.

Definitely a worry that the two big boys have this scenario, in what is definitely fi ground, but for now i see it as a valid option (disappointing one) as it not only limits the throw of the dice for South West uk, but also shortens the cold spell for those who get the snow.

The pub run may show the better option again, but i feel it will be at least Saturday before the attempt of breakdown is decided. Many of the twitter accounts from professional are eerily quiet and i think that tells the story. 

 

 

 

[Model output discussion - deep cold inbound?]

14 minutes ago, Man Without Beard said:

Based on all the models I've seen in the past 24 hours, this is my interpretation, well it was a picture or 1000 words  

I have to say, that is quite a good summary of the main potential this next week. All those lines can be adjusted in every direction and some surprises are likely too. i would add that the middle band could change to heavy snow followed by rain, but i am really in hope that does not happen.

I have a sneaky feeling that this may be a rare occasion where a satellite image shows all areas of mainland UK with a covering of snow. The potential is definitely there.

[Wales/Cymru Regional Weather Discussion]

Its a well known fact, that here in UK, we need the cold in first. We have no issues generally for precipitation.

However, in Wales and Southwest England we are in prime position, for breakdown or attempted breakdown scenarios.

These of course can be all or nothing, but good example is 2018, when Storm Emma crept into South Wales and dumped lots of the whitestuff over us.

Next week has opportunity for similar conditions

Embedded cold over UK, slider low pressure nudging into the cold.

The beg question is will Wednesdays low slip to far South, into France?

If so i expect the low behind it, to push a little further into UK.

Perfect conditions are these lows to just nudge in and not go to far North. its currently a viable option.

If they do push too far North it would be heavy snow followed by sleet / rain.

Either way next week looks like we will all see some snow and possibly disruptive sustained snow.

[Model output discussion - deep cold inbound?]

31 minutes ago, Kentspur said:

Intruguing bearing in mind we've an easterly and all the snow ends up in Wales

Thats  from a failed Atlantic attack, just one possibility, Snow fall and snow depth charts are pointless  at this stage for imby forecasting , What this is all showing is opportunities for just about everyone over the next few days if we can get that very cold air in place. Which seems more likely than not.  

[Model output discussion - deep cold inbound?]

1 minute ago, sebastiaan1973 said:

Wind and dewpoint. Control and Oper are on their own path from sunday.

There is something that is still making that an option. So although the option we want (most of us) is more likely, we can not completely ignore the op and control. I think the Met Office medium range forecast is something to cling on to. Many models and whatever they determine to look most likely from their model is indicating deep entrenched cold over the UK.  Tuesday / Wednesday next week may be quite interesting as the Atlantic has a failed attempt to push North East into the UK.  It may be Friday before we see complete model agreement beyond the weekend and even then snow forecasting limited to 48 / 72 hours.  I do see East coast UK doing very well from convective showers, but i am never overly confident when operational and control both see another option.  

[Model output discussion - is the beast awakening?]

4 minutes ago, Mr Brown said:

Umm 30mm is 3cm...

 

What he was saying to you is water content of precipitation that would result in 30mm (3cm) rain falls as around 10 times as much. So 3cm rain equals around 30cm snow. its a ball park figure but most snow conversion is 8-10 x rainfall amount.

Thats falling snow not necessarily settled snow

[Storm Christoph]

Predicted river level In England

That is rather serious

Here in Wales worst weather from now onwards. The rivers are responding very quickly to rainfall. 

Suspect we may see flood issues in South Wales. Parts of North wales Have already had 81mm

Maybe a severe flood alert for Northern England tomorrow

 

[Model Output Discussion - Snow for some, but what else is in store?]

feb1991blizzard

I have looked for closest model and run for his forecast, i would suggest it resembles the ECM 00Z closest. I am sure Mr Betts is a mildy too, can not remember for sure. I think safest bet is to see if the chief forecaster tomorrow  aligns with that forecast when they update the outlook. I think they will hedge all bets as i suspect beyond 4 days they are not massively in a better place than us. I think the rain will be the biggest concern for next few days and changing or reviewing the alerts and warnings as that evolves. 

 

[Model Output Discussion - Snow for some, but what else is in store?]

11 minutes ago, feb1991blizzard said:

Darren Bett is saying dry well into the extended, not just dry, very dry and seemed very confident.

Weather for the Week Ahead - BBC Weather

WWW.BBC.CO.UK

---

It's a wet start to the new week for many but will the weather trend change as we move closer to the weekend?

 

He does indeed, but that is meteogroup not Met Office. What i think you missed in that was what was happening with the high pressure on his chart. Longer term it looked rather interesting as it ridged in from The Atlantic into Europe, it then started to move north towards Scandinavia. A few more days on that forecast and i think a boom would be added to that forecast. 

So i think everything beyond Friday is up in the air (pun intended). However many of the different offerings from the models, including whatever Darren Betts used for his graphics, are hinting a cold in February.

How many times have we watched these type of fi offerings appear in February and come to fruition late February and early March as the days get longer and solar heating warmer. This year the offering started early and we have a good month of optimum time for snowfall.

 

[Wales/Cymru Regional Weather Discussion]

Afternoon all

Remember, when we see the toys being thrown from the Pram on the main model discussion thread its often due to IMBY scenarios.

As majority are from Central and Southern England, you will see messages suggesting nothing interesting and mild outlook. If Snow was to fall in Wales, they may often report a bad outlook as its not falling in their area.

However next week does look interesting.

Firstly Flooding risk Tuesday to Wednesday for Us Cumbria and North West Midlands. Quite significant rainfall for some, After this clears cold artic air flows in behind and we have opportunity for snow showers. After that we get a battleground scenario. Now i suggest that its 60% chance due to model consistency that 23rd to 25th Jan brings this battle ground to Wales, Exactly where is less certain. It will most likely be transient thou as less cold air more likely right at the end of January. That lasts into first week of February, but after that more cold air looks more likely with possible Easterly flow. That may lead to more battle ground scenarios and undercutting shortwaves. 

 

Main drivers for cold

SSW 

MJO currently in phase 3 but moving to COD and hopefully Phase 7

Against is the Current MJO Phase 3 (10+ day lag) and La Nina.

This is early winter and full of potential.

 

[Model Output Discussion - Snow for some, but what else is in store?]

MJO

The CA actually forecast it quite well a few days back So we can only assume its on to something.

Most now go from yesterdays placing ( The point that CA was best forecasting) to Cod, but CA wants to quickly move towards phase 7

If nothing else it shows us the volatility in the models just in regards to MJO.

 

[Model Output Discussion - Snow for some, but what else is in store?]

Okay i am going to try to calm the nerves a bit.

If we look back to a recent cold spell 2018 we can see the inconsistency in the models and the nerves on the threads here on net-weather

I have added some images that were being shared at the time. I also include a post about the SSW and how they see it modelled.

The Met office remained quiet until quite late on, although hinted at some cold periods and snow showers.

I am in South Wales and was pretty much snowed in.

The models at the time hinted at times of the cold spell, but also all the models at longer range played with a variety of outcomes. The trend is your friend here.

What we should be looking at is two main things

1. Changes in right direction between a model at same roll out time

So the GFS 12z against GFS 12Z  and ECM 12z against ECM 12Z (ECM 00Z v ECM 00Z)

Then look for cross model agreement, especially for trends and direction of any change. Again models on same run only.

So here are images of posts and model output back then.

The rule has been look for cold first, then snow later, if cold is not widespread look for trends that enhance it. Plus it took longer than expected in 2018 and for along time just showed up in fi, which may sound familiar. It can mean the models are picking up  a trend but enhancing it too quick. This weeks models appear to be doing a very similar thing

 

[Model Output Discussion - Snow for some, but what else is in store?]

A Southerly  Direction Jet would imply a amplified jet stream where the Southern flow is close to or over the UK. That would have probability of High pressure to the West of the Jet and lower pressure to our East side of the Jet.

A Jet to the South of the Uk  would be a good boundary of Colder and milder air, the jet would steer  low pressure along its path with tendency to attempt to move North out of the jet. This is probably the option that would be best for snow chances. We would hope for a slider low to effect  the Southern Uk and the precipitation to become snow on its Northern Edge. In this scenario there would most likely be convective showers bringing snow showers to much of the UK possibly over a prolonged period. The risk here is that Snow can evolve towards rain if it moves too far North and can be quite marginal ( High reward V high Risk)

A north jet would bring rain to the UK, Either we would be most likely on wrong side of the Jet stream ( Warmer side)  or it would likely drive less cold zonal weather off the warm Atlantic.

So of two jet profiles we would benefit most from, one is the North to South trajectory West of / or over UK, or a Jet stream South of the UK. 

Hopefully these images help, but importance is Southerly Jet stream or Southern trajectory Jet Stream ( North too South)

 

Please pick this apart as you may wish

[Model Output Discussion - Snow for some, but what else is in store?]

MJO appears to have peaked in phase 3 around 8th Jan,  I would expect the influence of phase 3 to start to ease (weaken) around 18th - 23rd.

(My study of this indicates 10-12 days for effect, which is different to what others suggest, but works for me)

The most likely phase is COD from now, and anyones guess from there. It is a complete mess with as much uncertainty there as in the 500mb charts and Surface pressure charts. All data beyond 5 days is up in the air. If any one of these is wrong then down stream everything else will to some extent be wrong.

The trend 00z run v 00Z Run etc  is not going our way at the moment, but we saw this in 2018. If we just view the run in comparison with previous run of same time we can figure out the minor changes early on that give such a different outcome. Then you can see if its feasible and likely.

What i will say, is getting precipitation here in UK has never been an issue, getting cold air in has. That cold air over the medium term has a very good chance of making progress towards the UK. Not shown consistently by models but hinted at  by them. 

Please see the latest phases and forecasted phases of MJO

 

[Model output discussion - cold spell approaching?]

Its not good for me, but Saturday looks like transient Snow for Brecon Beacons, then as it moves East  snow likely to lower levels from around line (Beige). Welsh Marches to West Midlands. This will only settle on some hills. Further East again (Orange line) Approx East of Northampton to Brighton, Snow is likely to fall and in lower elevations settling is possible. Ignore precipitation amounts, map just utilised to show where snow on Saturday is more likely.

[Model output discussion - cold spell approaching?]

1 hour ago, johnholmes said:

That's what i'm seeing too. Unless the dashes don't imply air mass direction.

 

See my comment above, no hey do not.

 

 

Hi John, i have followed your advice for years and aware of your background.

May i ask that you share your 500mb guidance so others can learn as they are by far the best use for longer term forecasting. Your knowledge and experience is very welcome here and sharing that knowledge again with new members can only make this a better place. Glad your still here and hope your well. pyro 

[Model output discussion - another cold spell on the horizon?]

5 minutes ago, Tim Bland said:

Have we really got that desperate it’s like the old days ..discussing the country file / long range forecasts...I can phone ‘weather call’ & check teletext if that helps They (Meteogroup) just present the ECM

I do not think that is fair Tim, Meteogroup utilise all the models not just ECM, they are also in agreement with Met O when severe weather warnings are issued. They have  MOU between them to ensure public gets the correct non conflicting messages.

With a SWW event i think its best to use every tool in the toolbox because this will have many twists and turns.

Icon and JMA all come into play if just for comparison

GFS often picks a trend in Fi but then drops it to bring it back last minute, the only things i do not use are piers Corbyn and the Express news paper.

Experts will be watching this very closely, a severe cold spell will put huge strain on NHS at best of times so people need to get it right. 

 

[Model output discussion - January cold spell ending, what next?]

Tempers will flair here and there will be no nails left on many fingers, if people keep trying to analyse every run  as they are doing.

To see where this is most likely to be going we need firstly look at trends ( 500mb charts are really useful)

Then Keep comparing same model against same run time to monitor changes, not the 6z against the 12z

Compare 12z against 12z for changes

The trend is your friend 

[Wales/Cymru Regional Weather Discussion]

4 minutes ago, Jayfromcardiff said:

I'll take a dusting of snow lol at this stage. Would you say it's worth even staying up for it? I'm not back in work until 4th jan anyway so not worried about sleep.

That choice is for you, the precipitation currently over Ireland is our first chance, i would suggest early to bed and get up around 5am.  just because you may be too tired to enjoy it if you stay up al night. 

[Wales/Cymru Regional Weather Discussion]

9 minutes ago, Jayfromcardiff said:

I live in Caerphilly now mate, bought a house there back last year. Should hopefully increase the chance of some snow.

That will help, further from the warm sea and a little more elevation

[Wales/Cymru Regional Weather Discussion]

Hi jay,

Best places are Brecon Beacons and north Valleys, saying that some transient snow in early hours possible in Cardiff, not sure it will settle thou.

Dew points hovering around 2 -3c but should lower with heavy precipitation.

More opportunities around 5th Jan too

This year actually looks quite interesting ( Winter 2020 - 2021)

 

[Wales/Cymru Regional Weather Discussion]

Seems this regional board is quiet right now, but with the weekend rainfall totals is suspect that we will see a tick up of posts both here and NW England thread.