Model Output Discussion - cold spell to end Autumn

[Optimus Prime]

4 minutes ago, jvenge said:

Well. Agree with trying to pick apart precipitation forecasts and thinking they wont change 5 days out, but at the same time, every model comes with a precipitation forecast and a breakdown of the type, quantity and location.

Therefore, I dont really understand this netweather weirdness of denying snow when it is shown or claiming snow when its not. We slip into forecast territory then, rather than actual output.

 

The only thing that needs to be said is they are rubbish. They are fairly good at forecasting rainfall intensity so as long as you aren't converting between precipitation intensity to precipitation type and the accumulative effect; effectively what the precip type algorithm does and is why it's always wrong at snow depths too, even within relatively high res. 

[Walsall Wood Snow]

Just now, MattStoke said:

I think it may be touch and go here. A slight southward and westward correct would be nice, from a totally selfish point of view! Hoping to catch the Cheshire Gap streamer on Friday, anyway.

What concerns me is not so much whether it will be rain or snow (I'd lean towards a fairly high likelihood for snow) but the possibility that if it is snow it might struggle to settle, possibly at all. It always seems a bit of a waste then anyway. Not that I know either way, but it's starting to look like it could be nothing more than one of those sort of events, which we've had the odd few of the last few Winters. Though granted never this early, so at least there's a long time yet for hopefully something better down the line.

[steveinsussex]

Steve M isn’t getting excited so that tells me enough

[weirpig]

1 minute ago, Man With Beard said:

Those snow charts need a public health warning though!! They often invent snow where there is none!!

I find the better ECM guide on weather.us is the "significant weather" charts

To honest m w b. Any precipitation charts at this distance are less than reliable 

[tight isobar]

8 minutes ago, weirpig said:

To honest m w b. Any precipitation charts at this distance are less than reliable 

And that goes for precip-accum...

And type!

Its got nowcast written ALL OVER IT!

My advice would be to enjoy the ride..

Then go for decipher within, 36-24 hrs of such.

Edited December 5, 2017 by tight isobar

[Mokidugway]

The uk will see snow , problem is it will be observed mostly by ptarmigans and the monarch of the glen 

[Nick L]

The EC Sunday event would bring buckets of snow to hills of northern England, Midlands southwards would see a brief spell of snow but any accumulations would be slushy and temporary.

[iowpompeylee]

30 minutes ago, ANYWEATHER said:

Plenty of scope from Friday into Sunday, for snow to fall just about anywhere, and even though Ive not got the dewpoint figures but as long as they are at freezing or below ,despite an air temperature above freezing, snow will fall.

Probably one of the most level headed comments I've seen on here all day! Bravo! 

Edited December 5, 2017 by iowpompeylee

[shaky]

3 minutes ago, Nick L said:

The EC Sunday event would bring buckets of snow to hills of northern England, Midlands southwards would see a brief spell of snow but any accumulations would be slushy and temporary.

Still time for it to change though nick!!if it goes any further south then it could be midlands and wales that get hammered!!higher chance of it goin north i think though!!

[snowray]

51 minutes ago, MKN said:

A few members keep saying midlands north wrt to snow. Gfs and ECM your looking at leeds north not the midlands.  

I think its more of a case of potential, certainly the North Midland might get involved, some snow charts are showing settled snow as far south as the M4 by the beginning of next week.

[Geordiesnow]

One more thing to note is the forecast very tight squeeze in the isobars has shifted southwards slightly so populated areas like Glasgow and Edinburgh could very well see gusts nearing 80,mph potentially if not slightly higher. Those really major gusts may not last all that long but the potential for disruption will be pretty high. Interesting times ahead for sure.

[gottolovethisweather]

On 04/12/2017 at 18:49, gottolovethisweather said:

And a couple of active fronts chasing the 528DAM line southwards. As stated in my previous post, I think this might also improve coldies hopes rather than anything else, as it might well produce deeper cold 850s than currently modelled. A lot for the professional forecasters to consider this week.

Also, I just saw my local tv forecast, goes from 13c Thursday to a max of 4c on Friday. Who knows where it'll go from there, but Fax charts will give us sound guidance as ever, thanks for sharing.

Well, the Fax charts are still proving their worth as we head into the period of greatest wintry (snow) potential. Come dawn on Friday, lying snow could well be affecting much of Scotland (including lowland parts of northern England perhaps?) and also parts of Western England, maybe into central parts too if conditions are ripe for it. Our first lowland snowfalls of the winter season 2017/18 are on their way, according to this D3 Fax Chart. As to my percentage chances of something significantly wintry occurring and lasting, I'll give it a 70:30 percent shot as no mild air is likely to kill off the wintry flavour for a good few days yet. The strongest depth of the cold will be felt from the 8th to 10th December as anticipated, previously. The more the snow settles, the greater our chances are of prolonging the cold spell IMHO. Timing is key with regards to the settling of any snowfall and the attached chart needs to come off as suggested for a coldies best hopes to happen. Bring on the chill and take care all, a certain Storm Caroline to deal with beforehand. Winter is just about to show its energetic and more seasonal side! 

Edited December 5, 2017 by gottolovethisweather

[MattStoke]

7 minutes ago, Walsall Wood Snow said:

What concerns me is not so much whether it will be rain or snow (I'd lean towards a fairly high likelihood for snow) but the possibility that if it is snow it might struggle to settle, possibly at all. It always seems a bit of a waste then anyway. Not that I know either way, but it's starting to look like it could be nothing more than one of those sort of events, which we've had the odd few of the last few Winters. Though granted never this early, so at least there's a long time yet for hopefully something better down the line.

I have seen snow settle heavily following a spell of torrential rain before, and that was in London! 

I notice most of the model output shows the snow on Friday missing me. However, a NW'ly always brings snow to Stoke, in my experience. What's even more odd is that the Met Office app forecast is showing sleet.

[feb1991blizzard]

1 minute ago, Nick L said:

The EC Sunday event would bring buckets of snow to hills of northern England, Midlands southwards would see a brief spell of snow but any accumulations would be slushy and temporary.

Just wondering Nick, what are the ECM snow charts like for verification, they look overdone on amounts to me, given they have predicted snow amounts in Manchester at least double anything that has happened in 40 years 3 times in the last week!!!   what I mean though is the GFS has a bias to snow when parameters in the run don't look favourable and rain looks more likely, what's the ECM like in this regard please?, I haven't tested the snow charts yet as ive only been using them just over a week.

[terrier]

Think the snowfall will correct further northwards next few days. Can see Newcastle northwards getting a good covering. With rest of us seeing cold rain. The gales look more worrying on Thursday. With Scotland seeing gusts in excess of 80mph. Then into next week looks like it could turn very wet for most of the uk. 

[Nick L]

Just now, feb1991blizzard said:

Just wondering Nick, what are the ECM snow charts like for verification, they look overdone on amounts to me, given they have predicted snow amounts in Manchester at least double anything that has happened in 40 years 3 times in the last week!!!   what I mean though is the GFS has a bias to snow when parameters in the run don't look favourable and rain looks more likely, what's the ECM like in this regard please?, I haven't tested the snow charts yet as ive only been using them just over a week.

Well the snow depth charts are derived so it depends on the algorithm used. Some totally exaggerate the reality. The ones I use at work are showing about 5cm or so but they tend to overegg it a little too.

[Winter Hill]

2 minutes ago, terrier said:

Think the snowfall will correct further northwards next few days. Can see Newcastle northwards getting a good covering. With rest of us seeing cold rain. The gales look more worrying on Thursday. With Scotland seeing gusts in excess of 80mph. Then into next week looks like it could turn very wet for most of the uk. 

Barrel of laughs you are 

[bobbydog]

34 minutes ago, blizzard81 said:

We have seen much worse charts over the last few years. That is true but where does it go from there? The azores high can only go east from that position which means the following charts would not look pretty at all. The intense pv to the north west is looking more ominous with each and every run. 

the "intense PV" is a lobe of the split vortex. another lobe is over the other side of the hemisphere in the north west pacific. there is an omnipresent HP cell over the pole. the vortex is shifting and splitting all over the place. people see purple over greenland and start to panic unnecessarily. it is likely a transient feature, not the powerful engine of a zonal jet like previous years.

Edited December 5, 2017 by bobbydog

[Snowmadsam]

Snowfall amounts in these sort of situations are very difficult to predict, especially in a northerly scenario. Take everything with a pinch of salt.

[Dean E]

I swear if I hear that 'North of the M4' again, i'll move to Alaska!

ECM joins the GFS with the uncertainties in my opinion, this is a very fluid (or solid) situation which needs more days and possible could be down to the 'nowcasting' time frame with this type of setup.

[Frosty.]

2 minutes ago, terrier said:

Then into next week looks like it could turn very wet for most of the uk. 

I think next week could be still on the cold side following the arctic outbreak with a mix of rain, sleet and snow, the snow risk especially further north and with elevation with a risk of further frosts and ice overnight.

[weirpig]

13 minutes ago, Nick L said:

The EC Sunday event would bring buckets of snow to hills of northern England, Midlands southwards would see a brief spell of snow but any accumulations would be slushy and temporary.

But about Midlands northwards:) 

[Mr Frost]

Will it snow in Carlisle though? That is the question...

All joking aside the weather looks very exciting IMBY over the next five days. (severe gales and a chance of snowfall - can’t ask for much more than that at the start of Winter!)

The GFS 18z will send all cold weather lovers to bed happy later tonight ...

Edited December 5, 2017 by Mr Frost

[Nick L]

To add a further perspective, the last frame of the 15z UKV goes out to +120 (Sunday 15:00) has it rain even on the leading edge south of Manchester.

[Team Jo]

Evening all - hello, hi! ? 

not entirely sure where the despair is coming from. OH WAIT it’s because it’s not microcasting to snow on your doorstep. Guess what! There’s a thread for that! It’s just not this one.

Please understand when you post something off topic that provokes a response, then lots of people reply, it makes this thread incredibly difficult to fathom. Even to those who have been around for lots of winters. In the space of my journey home I think I have scrolled through five pages of woe. Joy. Despondency. Joy. Despair.

At the rate some are going, you’re overlooking the fact we are about to hit a cold spell at all. In fact you might it whilst nitpicking every chart out to t+240...which surely sucks all the fun out of it, no?