Man With Beard

I made it 18 out of 51 ensemble members on the ECM 12Z that would likely lead to a covering of snow for the southern most counties (I didn't include the op or control as they generally returned less than 1cm). That's the most members for a couple of days. And yes, as you mention, there's the outside chance of a significant fall.

At least the current situation is worst case scenario for snow in central areas. There can only be more than zero!

I appreciate it doesn't happen every time but I'm always mindful of January 2010 - the time the entire country (except Bournemouth!) went white due to a feature only modelled within T48 - and that was on a northerly.

That's actually been very consistently modelled aside just a few runs. Actually, the whole thing has been modelled fairly consistently by the ensembles. There never was the promise of more than a few days of cold IMO.

Here's a Meteociel look at how the ECM mean has done for the famed 15th January, comparing the mean at D10 with this morning's op, which is now D4: That's absolutely brilliant.

This chart also shows reasonably tight clustering at -4C uppers or below until next Saturday? (This is London so colder further north)

It's hard to know what to wish for... last night's ECM was precarious with the cold combined with the channel low next Wednesday, but was very snowy across the ensembles ... this morning gets the cold further south but as a result a lot of ensemble members shift the snow into France... battleground snow always a risky and stressful business!

Member 27 of the ECM ensemble set, next Thursday. Foot of snow for many. Just for fun! just trying to cheer a few of you up

FWIW ... the majority of ECM ensembles have a snow event somewhere in England/Wales next Wednesday. Various clusterings, and no clear preference, for the event to be either south of M4, north of M4, or between Birmingham and Manchester (a few members still further north). All to play for!

Key point on this run, for me, is at T120. The Atlantic low has, at this point, retreated even further south, sucking up much more mild air towards the UK. So, when the low eventually reaches the UK, too much mild air over the top for the south - still ok further north. Precisely the way out of the cold snap some of us suggested even at the end of last week when all was looking rosy. That said, northern areas should still be fine as long as the low slides.

We're not used to pressure charts like this: occurring in combination with uppers like these: Although synoptically the GFS might not be precisely what coldies were after, it does deliver an alternative method of obtaining wintry weather in deep winter: Get the cold in first, and then any pattern that prevents mild southerlies pushing it out will be sufficient to sustain it. The cold gets in early next week (cross-model agreement getting better for that), and then a jet profile like the GFS is showing at D10 either locks the majority of mild air further south, or ushers it east before it can make sufficient inroads towards the UK: As a result, a pattern than looked lost to cold at D9 recovers quickly to this by D11: The moral of recent GFS runs, therefore: There's more than one way to crack a nut. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5004812

We're not used to pressure charts like this: occurring in combination with uppers like these: Although synoptically the GFS might not be precisely what coldies were after, it does deliver an alternative method of obtaining wintry weather in deep winter: Get the cold in first, and then any pattern that prevents mild southerlies pushing it out will be sufficient to sustain it. The cold gets in early next week (cross-model agreement getting better for that), and then a jet profile like the GFS is showing at D10 either locks the majority of mild air further south, or ushers it east before it can make sufficient inroads towards the UK: As a result, a pattern than looked lost to cold at D9 recovers quickly to this by D11: The moral of recent GFS runs, therefore: There's more than one way to crack a nut.

In all honesty I sense areas north of, say, Birmingham look in a fantastic position - the cold looks like getting in, the Atlantic doesn't look aligned in a way to mix milder air to northern areas, and plenty of instability to come. Not a cert but odds are good. It's the southern half which I suspect have a gut wrenching few days ahead.

Only one ECM cluster T192-T240, which either means good agreement or absolutely no agreement. A quick look at the individual ensembles confirms - it's the latter. Absolutely chaos for the UK on the 51 ECM members - snow, mild, dry, wet, wind, calm, it really could be anything for anyone by the middle of next week. No basis at all for a confident forecast after Monday.

UKMO T144 850s - reading the script for the 15th January so it seems, and at just D6 now:

Looks like the UKMO has ditched the idea of sending the Atlantic low into France altogether - which clears the way for a stronger push from the north by T144. Perhaps this is the new development to look for?

Trouble is ... it's a very plausible run

Well I thought so! Guess it depends what you want. If you are content with one cold and snowy week, then the GFS is awesome tonight. If you want a reprise of 1947 (as some seem to have as their bar) then naturally even the cold and snow on the GFS won't be enough

GFS has much better orientation of the low to the SW for extended cold, as it sweeps the low into France by D9. Massive snowstorm for the south. What could possibly go wrong

Should the Scandi trough verify precisely like that, it should be enough for a cold spell nationwide of at least a few days - however, there remains sufficient margin for error in southern/western areas from a synoptics point of view to avoid deep cold in these parts.

Uppers below 4C right down to the south coast for several days next week on ECM mean. Suggests the cold, once in, may not be forced out quickly.

The extra Iberian heights is always my fear - so often they get ramped up D6-D7. On this occasion it seems the Greenland side has also slipped. THAT SAID! There's still lots of ensemble members that retain the pattern of 3 days ago, and we know they all run at the same resolution as the op

Looking at the individual ECM ensembles for 15 January, the cold signal is distinctively "dodgy". There are still a good number of Greenland High members but there is no ascendancy in either the cold or mild camp. We're back in a waiting game.

Unbelievable cold coming across the Arctic by T264. Any chance it might get here?

Knife edge stuff at T192. That low in the Atlantic needs to keep coming!!